JOURNAL OF PLANT NUTRITION
Vol 27 No 7 pp 1199ndash1226 2004
Switchgrass Response to Harvest Frequency
and Time and Rate of Applied Nitrogen
W E Thomason1 W R Raun2 G V Johnson2
C M Taliaferro2 K W Freeman2 K J Wynn2
and R W Mullen2
1Samuel Roberts Noble Foundation
Ardmore Oklahoma USA2Department of Plant and Soil Science Oklahoma
State University Stillwater Oklahoma USA
ABSTRACT
Switchgrass (Panicum virgatum L) is currently being evaluated as
a raw material for producing fuel chemicals and electricity
Switchgrass biomass is bound by the growing environment that
includes fertility More information is needed on sustainable switch-
grass production as influenced by nitrogen fertility and harvest
management Field experiments were initiated at Chickasha and
Perkins OK in 1996 and 1998 respectively to evaluate switchgrass
Contribution from the Oklahoma Agricultural Experiment Station
Correspondence W E Thomason Virginia Polytechnic Institute and State
University Department of Crop and Soil Environmental Sciences 422 Smyth
Hall Blacksburg VA 24061 USA Fax 540-231-3075 E-mail wthomaso
vtedu
1199
DOI 101081PLN-120038544 0190-4167 (Print) 1532-4087 (Online)
Copyright amp 2004 by Marcel Dekker Inc wwwdekkercom
ORDER REPRINTS
response to applied nitrogen (N) at rates of 0 112 224 448 and
896 kg ha1 In addition harvest frequency and time of N application
were evaluated Yield maximums and the greatest N potassium (K)
phosphorus (P) and sulfur (S) uptake values were achieved with
448 kgNha1 applied all in April and harvested three times In fact
harvest frequency was the most important factor affecting yields
over the course of these studies with average dry matter yields of
163 147 and 129Mgha1 yr1 for three two and one harvest
yr1 respectively No significant change in soil organic carbon was
detected over time Although dry matter yields were found to decline
with time total N uptake did not Forage N concentration was found
to be greater in later years thus increasing production costs While
yields were highest (180Mgha1) with 448 kgNha1 applied all in
April and three harvests applying 0N and harvesting three times
produced almost as much total biomass (169Mgha1) This limited
response to N is possibly explained by the evolution of switchgrass
under low N conditions Increasing forage concentrations of K
magnesium (Mg) P and S were noted with increasing yields
indicating a potential for response to these nutrients
Key Words Switchgrass Panicum virgatum Nitrogen Biofuel
INTRODUCTION
Evaluation of switchgrass has shown that it is suitable for use as anenergy feedstock either for producing ethanol via bioconversiontechniques or electricity via co-firing with coal It is also beinginvestigated as a replacement for wood pulp in the paper makingprocess The energy content of switchgrass has been found to becomparable to that of wood and when the expected costs of productionare weighed against the value of the crop switchgrass was capable ofproducing five times more energy than that required to grow the crop[1]
Analysis of ash and alkali content of switchgrass has shown relatively lowalkali levels and therefore should have little slagging potential when usedin coal firing systems[1] This same research noted that due to the highcellulose content low ash levels and good fiber length to width ratiosswitchgrass could substitute for hardwood pulp in production of highquality paper Later work estimates the cost of switchgrass production ataround $30 t1 indicating that it would be viable at least on a cost basisas a replacement for wood pulp[2]
Nutrient uptake and loss from production sites are important issuesfor high-biomass producing crops such as switchgrass This is especially
1200 Thomason et al
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true if removal as in haying and not grazing is practiced Mineralcontent of switchgrass has been found to be higher on a percentage scalewith lower yields for the macronutrients N P K and calcium (Ca) Nochange in concentration for many micronutrients has been noted butconcentrations of boron (B) and manganese (Mn) have been found toincrease with increasing yields[3] Increases in plant N concentration withincreased applied N throughout the season have been noted[4] Staleyet al[5] found increasing N concentration in harvested plant parts withincreases in applied nitrogen They also found increased N uptake withincreased N rates but only in a one-harvest system Using 15N as a tracerthey attributed only 15ndash39 of total N uptake to fertilizer sources butthese uptake levels were still above those of tall fescue grown on the samemarginal sites Researchers in Pennsylvania have found N recoveries of40 of that applied and noted that this number was thought to decreaseas native soil N levels increased Measured on a daily basis switchgrasshas been found to take up 149ndash263 kgNha1 d1[6] Other researchstates that if water is not limiting then N levels account for 80 of thevariation in yields When water is limiting however the absence ofmoisture is the most important factor in yield determination[7] Depth ofsoil has been found to have little effect on N uptake[8]
Harvesting methods involving one to two cuttings each season havebeen shown to produce optimum yields in most systems[9] The earlierharvest is usually much higher in animal feed value and a two-cut systemmay allow early cuttings to be used as livestock feed and later cuttings forbiofuel production[10] Sanderson[11] found that as switchgrass maturesthrough the growing season stem components increase and leaf compo-nents decrease as a percent of total dry biomass This increase in stemportion is attributed to internode elongation necessary for plant growthand competitiveness
Switchgrass yields of 10ndash12Mgha1 have been reported inCanada[12] This led the authors to surmise that switchgrass could be avaluable source of biomass for biofuel production Hall et al[13] foundswitchgrass yields in Iowa to be near 6Mgha1 and noted a consistentresponse to added N up to 75 kgNha1
Bransby et al[14] noted switchgrass environmental benefits as an Nbuffer strip crop and as a net fixer of carbon (C) They state that the mostimportant benefit of using switchgrass as a fuel is the net cycling of C in theenvironment and give only slight importance to soil C sequestrationLong-term research in Alabama has recently shown no change in soilorganic C levels after 3 yrs in continuous switchgrass but after 10 yrs soilorganic C was 45 higher than adjacent fallow ground[15] The objectivesof this study were (1) to evaluate the response in biomass yield and uptake
Switchgrass Response to Applied Nitrogen 1201
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of N K P Ca Mg and S of switchgrass grown in Oklahoma to harvestfrequency and time and rate of applied nitrogen and (2) to evaluate theshort term effects of switchgrass production on soil organic C levels
MATERIALS AND METHODS
Two field experiments were initiated to evaluate switchgrass responseto applied N at rates of 0 112 224 448 and 896 kg ha1 In additionharvest frequency (once at the end of September twice mid-July andSeptember and three times May mid-July and September) and time ofN application (all in April 12 in April and 12 following first harvestand 13 in April 13 following first harvest and 13 following secondharvest) were evaluated (Table 1) Experiments were initiated atChickasha (Dale silt loam fine-silty mixed superactive thermic PachicHaplustoll) and Perkins (Teller sandy loam fine-loamy mixed thermicUdic Arguistoll) OK in 1996 and 1998 respectively Pre-establishmentsoil test values and soil classifications for the sites are reported in Table 2A randomized complete block design with three replications was used atboth locations with an incomplete factorial arrangement of treatments(Table 1) The northern lowland switchgrass variety lsquolsquoKanlowrsquorsquo wasbroadcast seeded in 1996 at Chickasha and 1998 at Perkins at a rate of11 kg pure live seed ha1 The stand at Chickasha was allowed a one-yearestablishment phase and harvesting began the following spring whilePerkins was planted and harvesting begun in the same year At both sitespreplant rates of 112 kgNha1 224 kg P2O5 ha
1 and 560 kgK2Oha1
were applied to the entire area Switchgrass was harvested at a heightof 10ndash15 cm using a lsquolsquoCarterrsquorsquo harvester
Forage samples were dried and ground to pass a 140-mesh sieve(100 um) and analyzed for total N content using a Carlo-Erba NA 1500automated dry combustion analyzer[16] Forage samples were alsoanalyzed for tissue concentrations of P K[17] Ca Mg and S[18]
Nutrient uptake values were calculated by multiplying the yield inkg ha1 by the elemental in the dry forage
Surface soil samples (0ndash15 cm) were taken from both experiments atinitiation and analyzed for organic carbon using dry combustion[16] Inspring 2001 bulk density samples were taken with a Giddings soil probefrom the experimental area and an adjacent area that was conventionallytilled for comparison Also in spring 2001 surface soil samples (0ndash15 cm)samples were taken between plant crowns to simulate the initial samplingand also from within the crown of the plant to evaluate samplingmethods Soil organic carbon levels (mgC cm2) were calculated as
1202 Thomason et al
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a product of bulk density (g soil cm3) core depth (cm) and soil carbonconcentration (mgCg1 soil)
Statistical evaluation and analysis of variance were performedusing SAS[19]
RESULTS
Chickasha
The Chickasha site was the only one established in time for the 1997summer harvests Central Oklahoma received timely and adequaterainfall throughout the summer and maximum production levels werein excess of 30Mgha1 (Table 3) Three harvests one early in the
Table 1 Treatment structure for switchgrass experiment Chickasha (initiated
1996) and Perkins (initiated 1998)
Trt N rate N application method of harvests
1 0 mdash One
2 0 mdash Two
3 0 mdash Three
4 112 All in April One
5 224 All in April One
6 448 All in April One
7 896 All in April One
8 112 All in April Two
9 224 All in April Two
10 448 All in April Two
11 896 All in April Two
12 112 All in April Three
13 224 All in April Three
14 448 All in April Three
15 896 All in April Three
16 112 12 in April 12 aft 1st harvest Two
17 224 12 in April 12 aft 1st harvest Two
18 448 12 in April 12 aft 1st harvest Two
19 896 12 in April 12 aft 1st harvest Two
20 112 13 in April 13 aft 1st harv 13 aft 2nd harv Three
21 224 13 in April 13 aft 1st harv 13 aft 2nd harv Three
22 448 13 in April 13 aft 1st harv 13 aft 2nd harv Three
23 896 13 in April 13 aft 1st harv 13 aft 2nd harv Three
Switchgrass Response to Applied Nitrogen 1203
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Table
2
Initialsoilchem
icalcharacteristics
(0ndash15cm
)andclassificationatChickashaandPerkinsOK
Location
pH
a
NH
4-N
NO
3-N
Pb
Kb
TotalN
cOrganic
Cc
Dbinitial
Db2001
(mgkg1)
(mgg1)
(gcm
3)
Chickasha
69
758
112
28
215
006
82
143
141
ClassificationDale
siltloam
(fine-siltymixedsuperactive
thermic
Pachic
Haplustoll)
Perkins
67
753
21
77
325
09
68
147
147
ClassificationTellersandyloam
(fine-loamymixedactive
thermic
Udic
Argiustoll)
Dbbulk
density
(gcm
3)
apH11
soilwater
bPandKMehlich
III
cOrganic
CandtotalNdry
combustion
1204 Thomason et al
ORDER REPRINTS
summer one in late summer and one at the end of the season producedmore biomass (277Mgha1) compared to one harvest at the end of theseason (186Mgha1) These results reflect the ideal weather conditionspresent in 1997 that resulted in high yields Three harvests resulted inhigher N uptake values than those with fewer cuttings even when yieldswere higher for plots with fewer cutting dates (Table 3) The lowest Nuptake values for any treatment occurred with lower N rates (less than224 kg ha1) and one or two cuttings Three harvests increased K uptakeby the plants and split-applying the N over three dates resulted in more Kuptake than with two N application dates Neither treatment removed asmuch K as those with all N applied in April This is plausible consideringthe amount of K removed in the stems Phosphorus uptake levels wereon average approximately ten times lower than N or K uptake levelsThis was expected based on previous work documenting NP ratios of101[20] Splitting N applications over two dates resulted in lower Premoval than when applying all N early in the season (Table 3)
In 1998 a significant response to applied N was observed Howeverno differences in harvest frequency were noted probably due to the lackof rainfall in mid-summer Total yields were much lower than in 1997Lower rates of early season N and the removal of forage in late-summerdecreased yields in plots with three harvests and three-way split Napplications when compared to those cut twice Although yields werelower in 1998 maximum N uptake was higher than 1997 (375 and330 kg ha1 respectively) There was no difference in N uptake untiltotal N rates reached 224 kg ha1 Potassium uptake values were foundto follow the same trend as N Maximum K uptake occurred withthree-harvests and lowest values with one-harvest (Table 4)
Yields were again high at the Chickasha site in 1999 with some plotsproducing over 20Mgha1 (Table 5) The average yield for the site was17Mgha1 The highest levels of N uptake were observed with splitapplications of N and multiple harvests Uptake of K mirrored that forN in that number of harvests was highly significant and multipleharvests tended to remove more K than one harvest Phosphorus uptakewas greatest for three harvests regardless of N timing (353 and154 kg ha1 for three and one harvest respectively)
Yields for 2000 represent only the first two scheduled harvests for theyear and not the final end of season harvest Due to heavy fall rainsharvest was delayed and due to lack of communication the area wasburned before the final harvest could be taken Therefore yields shown inTable 6 represent the sum of only two cuttings The highest yields werecut two times (scheduled for three) and either not fertilized or fertilizedat the lowest rate of 112 kgNha1 (154 and 157Mgha1) Nitrogen
Switchgrass Response to Applied Nitrogen 1205
ORDER REPRINTS
Table
3
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1997
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
238501
10941
28072
258
441
1491
191
Cutting
24132329
b709443
b1344882
b6236
b9809
11234
b4789
b
Ntiming
3361873
10535
37908
134
30
19
58
Nrate
31564708
a209208
a171088
a15333
2605
2557
534
a
CuttingaN
rate
8707859
56216
26387
393
1526
2166
302
NtimingaN
rate
6651074
41644
60091
527
1232
2031
314
Residualerror
44
478953
38207
52088
473
1924
1917
288
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
222
1650
1689
195
386
400
131
112
1harvest
174
1177
1247
134
337
372
104
224
1harvest
164
1406
1285
154
284
310
100
448
1harvest
169
1186
1311
135
322
352
105
896
1harvest
203
1541
1489
173
394
390
127
02harvests
334
2548
2612
296
552
600
208
112
2harvests
155
1536
1521
161
403
344
118
1206 Thomason et al
ORDER REPRINTS
224
2harvests
337
2825
2694
284
643
688
222
448
2harvests
296
2830
2842
310
531
589
206
896
2harvests
244
2311
2337
217
403
464
163
03harvests
267
2325
3136
267
520
594
182
112
3harvests
249
2151
2902
244
348
389
193
224
3harvests
277
2608
3358
293
420
432
237
448
3harvests
309
3000
3814
333
425
473
265
896
3harvests
286
3202
3275
268
420
449
250
112
2-spN2harv
241
2037
1976
216
420
490
160
224
2-spN2harv
253
2091
1958
219
482
492
162
448
2-spN2harv
367
3306
3413
382
626
691
243
896
2-spN2harv
202
1950
1714
212
416
424
148
112
3-spN3harv
247
2101
2677
237
354
416
220
224
3-spN3harv
199
1821
2191
202
322
342
164
448
3-spN3harv
318
2145
3687
325
490
485
251
896
3-spN3harv
291
2739
3411
313
433
469
254
SED
57
505
589
53
113
113
44
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1207
ORDER REPRINTS
Table
4
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2996539
a87600
205053
a636
9278
15536
1010
Cutting
2372035
414096
a653177
b1024
1009
1563
266
Ntiming
3576196
111018
185774
a936
4895
6344
804
Nrate
3811575
a33003
62676
a527
a4584
a5872
336
a
CuttingaN
rate
8239068
59376
64205
400
6028
10433
560
NtimingaN
rate
6168684
34597
43532
180
2624
7172
282
Residualerror
44
220581
50460
52109
412
3338
4005
318
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
166
2048
1902
221
689
592
180
112
1harvest
141
1780
1875
195
601
638
164
224
1harvest
158
2127
2119
207
698
668
183
448
1harvest
172
2170
2212
211
726
747
200
896
1harvest
100
1328
1256
117
434
430
114
02harvests
166
2232
2468
225
677
776
205
112
2harvests
112
1548
1610
169
436
438
124
224
2harvests
226
3000
3378
311
910
1046
277
1208 Thomason et al
ORDER REPRINTS
448
2harvests
147
1956
1855
187
309
300
98
896
2harvests
162
2265
2241
191
575
680
190
03harvests
215
3403
3473
280
671
819
228
112
3harvests
168
2352
2705
201
533
658
184
224
3harvests
205
2833
3432
253
616
716
205
448
3harvests
245
3756
3864
289
641
668
190
896
3harvests
147
2229
2377
189
487
537
165
112
2-spN2harv
175
2119
2455
247
614
757
213
224
2-spN2harv
200
2677
3123
289
777
846
258
448
2-spN2harv
158
2070
2464
212
601
725
200
896
2-spN2harv
156
2355
2207
220
621
609
201
112
3-spN3harv
141
1962
2110
164
425
522
140
224
3-spN3harv
146
2233
2228
183
520
567
169
448
3-spN3harv
175
2375
2739
219
531
619
172
896
3-spN3harv
135
2210
2376
172
463
534
162
SED
12
580
589
52
149
163
46
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1209
ORDER REPRINTS
Table
5
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2464423
865906
1102070
a13008
a1665
6961
a291
Cutting
245101
952918
a1038877
b14290
b139
209
2203
b
Ntiming
3120137
133208
134666
1091
3230
2274
789
a
Nrate
32430687
717517
596007
4215
1799
2500
102
CuttingaN
rate
8207490
28101
43658
250
4465
b4667
a380
NtimingaN
rate
62060595
493140
380903
3444
810
1207
159
Residualerror
44
1562737
391299
334675
3504
1491
1808
291
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
109
781
1011
124
328
380
93
112
1harvest
150
1577
1541
171
478
532
145
224
1harvest
162
1459
1954
189
436
581
131
448
1harvest
191
1800
2386
181
693
715
180
896
1harvest
114
1257
1095
104
345
363
98
02harvests
179
2278
2736
274
543
602
192
112
2harvests
132
1754
2237
211
416
432
149
224
2harvests
170
2210
2453
244
530
614
182
1210 Thomason et al
ORDER REPRINTS
448
2harvests
162
2172
2291
221
352
400
120
896
2harvests
173
2474
2514
216
534
584
180
03harvests
200
2750
3273
352
500
559
205
112
3harvests
185
3150
3450
379
533
515
249
224
3harvests
167
2787
3303
335
392
436
184
448
3harvests
191
3300
3491
368
480
530
207
896
3harvests
154
2857
3000
331
431
472
194
112
2-spN2harv
145
1794
2258
226
432
469
156
224
2-spN2harv
146
1808
2078
223
564
501
195
448
2-spN2harv
175
2181
2713
248
487
557
171
896
2-spN2harv
208
2702
3557
288
654
703
220
112
3-spN3harv
155
2220
2522
260
353
381
145
224
3-spN3harv
152
2501
2949
304
412
401
174
448
3-spN3harv
180
2707
3137
354
405
475
170
896
3-spN3harv
263
3328
3144
425
366
401
167
SED
102
1573
1494
153
100
110
38
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1211
ORDER REPRINTS
Table
6
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2194823
b35769
a23391
1497
b1151
2969
b240
a
Cutting
2325370
b727339
b1445641
b9451
b2978
b1602
769
b
Ntiming
318979
a10279
15723
60
663
380
28
Nrate
3131730
b13237
24928
765
344
1865
a124
CuttingaN
rate
874236
a32484
a29096
491
1268
a1213
105
NtimingaN
rate
629574
7762
26341
384
237
239
41
Residualerror
44
31244
8263
16602
157
352
385
52
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
mdashmdash
mdashmdash
mdashmdash
mdash
112
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
224
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
448
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
896
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
02harvests
140
1493
1923
217
320
439
132
112
2harvests
110
1252
1516
203
264
345
106
224
2harvests
125
1334
1942
193
277
418
109
1212 Thomason et al
ORDER REPRINTS
448
2harvests
117
1485
1232
185
264
361
114
896
2harvests
102
1509
1217
152
315
338
104
03harvests
154
2564
3177
317
389
481
171
112
3harvests
157
2560
3317
347
387
507
170
224
3harvests
141
2477
3183
336
376
434
177
448
3harvests
154
2719
3084
342
384
451
180
896
3harvests
92
1676
2012
170
218
258
110
112
2-spN2harv
103
1123
1262
167
225
319
97
224
2-spN2harv
125
1265
1468
192
282
404
108
448
2-spN2harv
107
1212
1350
185
232
353
98
896
2-spN2harv
106
1419
1490
164
260
325
101
112
3-spN3harv
139
2238
2762
280
346
418
154
224
3-spN3harv
120
2194
2474
268
281
361
145
448
3-spN3harv
144
2504
3053
336
338
441
178
896
3-spN3harv
112
2013
2427
259
253
297
134
SED
14
235
333
32
49
51
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1213
ORDER REPRINTS
uptake of 240 kgNha1 was highest for two harvests (scheduled for
three) and April fertilization (Table 6) Potassium uptake was highest
with multiple harvests The lack of the final harvest for this data set
severely limited interpretation
Perkins
Yields in 1998 were lower than those at Chickasha due to sandier
soil and less total rainfall Treatment combinations with two or three
harvests and split N applications produced the highest yields averaging
over 11Mgha1 Forage nitrogen concentration did not increase
with increasing yields as was the trend over all years (Fig 1) Potassium
uptake was maximized with two harvests and either one or two N
applications both averaging near 180 kgKha1 Uptake of P was
significantly affected by N rate and was greatest with one harvest and
one N application date at 174 kg ha1 (Table 7) Phosphorus uptake
decreased with multiple harvestsPerkins again produced much lower yields than Chickasha in 1999
and significant differences were noted due to number of harvests and N
timing (Table 8) Average yields were highest for the three harvests three-
way split N treatments (Table 8) Multiple harvests increased crop N
uptake over those with the same total N rates and one harvest Potassium
uptake was high for all multiple harvest plots In fact one harvest
0
05
1
15
2
25
3
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
KN
y = 00002x - 16581 R2= 07749
y = 5E-05x + 04825 R2= 02171
Figure 1 N and K concentrations with increasing dry biomass yields Chickasha
and Perkins (View this art in color at wwwdekkercom)
1214 Thomason et al
ORDER REPRINTS
removed little more than half of the K of two or three harvests (775 vs1552 kg ha1) Three harvests also resulted in increased P uptake
Dry matter yield in 2000 averaged over N rate was 133Mgha1
(Table 9) Nitrogen removal was maximized with three harvests andsplitting N into three applications (Table 9) There was a trend towardincreased N uptake with increasing harvest frequency and increasing Nrate Three harvests with N split into three increments resulted in 48more K uptake than two harvests and two N application dates (896 vs1844 kg ha1) The highest average P uptake was found for three harvestsand three-way split N applications (202 kg ha1) (Table 9)
Soil Carbon
Organic C data from in crown and between crown samples werecompared to organic C from initial samples from the area to determine ifchanges had occurred Bulk density measurements taken from theexperimental area did not differ from an adjacent area that wasconventionally tilled Initial samples indicated average soil organic C(SOC) for the site of 68 and 82mg g1 for Perkins and Chickasharespectively These results are possibly confounded by known spatialvariability in SOC reported by Raun et al[21] Contrast comparisons founda significant linear decrease in SOC with increasing N rates and twoharvests for the Chickasha crown sampling (Table 10) A significantquadratic increase was noted for Perkins in crown samples and asignificant quadratic decrease in SOC with increasing N rate was foundfor between crown samples at Chickasha Taken together there seem to beno obvious trends toward increasing or decreasing SOC at either site Thisis potentially influenced by the fact that aboveground biomass wasremoved from the site Garten and Wullschleger[22] have estimated that itmay take a decade of switchgrass production to sequester a significantmeasurable amount of soil carbon Given more time SOC may increasebut the short duration (3ndash5 yrs) of this study has provided no real evidencesupporting this increase in SOC especially in the lsquolsquobetween crownrsquorsquosamples
CONCLUSIONS
Overall forage K concentrations increased with increasing yieldwhile N concentrations were not affected (Fig 1) This suggests anincreased likelihood of obtaining a response to K rather than N in
Switchgrass Response to Applied Nitrogen 1215
ORDER REPRINTS
Table
7
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
273649
35478
70045
b2962
b18430
b2215
a151
Cutting
239889
137708
102599
b392
18
1398
56
Ntiming
31062
151319
7734
76
4818
105
14
Nrate
3118782
a202660
47764
157
a1925
1045
184
CuttingaN
rate
850489
92751
21729
a164
2875
1466
165
NtimingaN
rate
622391
217859
21916
189
3453
1344
161
Residualerror
44
28679
173477
12329
94
2004
620
112
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
106
1889
972
162
442
261
147
112
1harvest
84
1239
1058
136
577
268
124
224
1harvest
102
1812
1033
173
448
276
145
448
1harvest
119
1970
1530
177
535
326
166
896
1harvest
104
2349
1840
222
522
323
178
02harvests
87
1110
1283
112
330
257
110
112
2harvests
103
1596
1662
139
534
350
147
1216 Thomason et al
ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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response to applied nitrogen (N) at rates of 0 112 224 448 and
896 kg ha1 In addition harvest frequency and time of N application
were evaluated Yield maximums and the greatest N potassium (K)
phosphorus (P) and sulfur (S) uptake values were achieved with
448 kgNha1 applied all in April and harvested three times In fact
harvest frequency was the most important factor affecting yields
over the course of these studies with average dry matter yields of
163 147 and 129Mgha1 yr1 for three two and one harvest
yr1 respectively No significant change in soil organic carbon was
detected over time Although dry matter yields were found to decline
with time total N uptake did not Forage N concentration was found
to be greater in later years thus increasing production costs While
yields were highest (180Mgha1) with 448 kgNha1 applied all in
April and three harvests applying 0N and harvesting three times
produced almost as much total biomass (169Mgha1) This limited
response to N is possibly explained by the evolution of switchgrass
under low N conditions Increasing forage concentrations of K
magnesium (Mg) P and S were noted with increasing yields
indicating a potential for response to these nutrients
Key Words Switchgrass Panicum virgatum Nitrogen Biofuel
INTRODUCTION
Evaluation of switchgrass has shown that it is suitable for use as anenergy feedstock either for producing ethanol via bioconversiontechniques or electricity via co-firing with coal It is also beinginvestigated as a replacement for wood pulp in the paper makingprocess The energy content of switchgrass has been found to becomparable to that of wood and when the expected costs of productionare weighed against the value of the crop switchgrass was capable ofproducing five times more energy than that required to grow the crop[1]
Analysis of ash and alkali content of switchgrass has shown relatively lowalkali levels and therefore should have little slagging potential when usedin coal firing systems[1] This same research noted that due to the highcellulose content low ash levels and good fiber length to width ratiosswitchgrass could substitute for hardwood pulp in production of highquality paper Later work estimates the cost of switchgrass production ataround $30 t1 indicating that it would be viable at least on a cost basisas a replacement for wood pulp[2]
Nutrient uptake and loss from production sites are important issuesfor high-biomass producing crops such as switchgrass This is especially
1200 Thomason et al
ORDER REPRINTS
true if removal as in haying and not grazing is practiced Mineralcontent of switchgrass has been found to be higher on a percentage scalewith lower yields for the macronutrients N P K and calcium (Ca) Nochange in concentration for many micronutrients has been noted butconcentrations of boron (B) and manganese (Mn) have been found toincrease with increasing yields[3] Increases in plant N concentration withincreased applied N throughout the season have been noted[4] Staleyet al[5] found increasing N concentration in harvested plant parts withincreases in applied nitrogen They also found increased N uptake withincreased N rates but only in a one-harvest system Using 15N as a tracerthey attributed only 15ndash39 of total N uptake to fertilizer sources butthese uptake levels were still above those of tall fescue grown on the samemarginal sites Researchers in Pennsylvania have found N recoveries of40 of that applied and noted that this number was thought to decreaseas native soil N levels increased Measured on a daily basis switchgrasshas been found to take up 149ndash263 kgNha1 d1[6] Other researchstates that if water is not limiting then N levels account for 80 of thevariation in yields When water is limiting however the absence ofmoisture is the most important factor in yield determination[7] Depth ofsoil has been found to have little effect on N uptake[8]
Harvesting methods involving one to two cuttings each season havebeen shown to produce optimum yields in most systems[9] The earlierharvest is usually much higher in animal feed value and a two-cut systemmay allow early cuttings to be used as livestock feed and later cuttings forbiofuel production[10] Sanderson[11] found that as switchgrass maturesthrough the growing season stem components increase and leaf compo-nents decrease as a percent of total dry biomass This increase in stemportion is attributed to internode elongation necessary for plant growthand competitiveness
Switchgrass yields of 10ndash12Mgha1 have been reported inCanada[12] This led the authors to surmise that switchgrass could be avaluable source of biomass for biofuel production Hall et al[13] foundswitchgrass yields in Iowa to be near 6Mgha1 and noted a consistentresponse to added N up to 75 kgNha1
Bransby et al[14] noted switchgrass environmental benefits as an Nbuffer strip crop and as a net fixer of carbon (C) They state that the mostimportant benefit of using switchgrass as a fuel is the net cycling of C in theenvironment and give only slight importance to soil C sequestrationLong-term research in Alabama has recently shown no change in soilorganic C levels after 3 yrs in continuous switchgrass but after 10 yrs soilorganic C was 45 higher than adjacent fallow ground[15] The objectivesof this study were (1) to evaluate the response in biomass yield and uptake
Switchgrass Response to Applied Nitrogen 1201
ORDER REPRINTS
of N K P Ca Mg and S of switchgrass grown in Oklahoma to harvestfrequency and time and rate of applied nitrogen and (2) to evaluate theshort term effects of switchgrass production on soil organic C levels
MATERIALS AND METHODS
Two field experiments were initiated to evaluate switchgrass responseto applied N at rates of 0 112 224 448 and 896 kg ha1 In additionharvest frequency (once at the end of September twice mid-July andSeptember and three times May mid-July and September) and time ofN application (all in April 12 in April and 12 following first harvestand 13 in April 13 following first harvest and 13 following secondharvest) were evaluated (Table 1) Experiments were initiated atChickasha (Dale silt loam fine-silty mixed superactive thermic PachicHaplustoll) and Perkins (Teller sandy loam fine-loamy mixed thermicUdic Arguistoll) OK in 1996 and 1998 respectively Pre-establishmentsoil test values and soil classifications for the sites are reported in Table 2A randomized complete block design with three replications was used atboth locations with an incomplete factorial arrangement of treatments(Table 1) The northern lowland switchgrass variety lsquolsquoKanlowrsquorsquo wasbroadcast seeded in 1996 at Chickasha and 1998 at Perkins at a rate of11 kg pure live seed ha1 The stand at Chickasha was allowed a one-yearestablishment phase and harvesting began the following spring whilePerkins was planted and harvesting begun in the same year At both sitespreplant rates of 112 kgNha1 224 kg P2O5 ha
1 and 560 kgK2Oha1
were applied to the entire area Switchgrass was harvested at a heightof 10ndash15 cm using a lsquolsquoCarterrsquorsquo harvester
Forage samples were dried and ground to pass a 140-mesh sieve(100 um) and analyzed for total N content using a Carlo-Erba NA 1500automated dry combustion analyzer[16] Forage samples were alsoanalyzed for tissue concentrations of P K[17] Ca Mg and S[18]
Nutrient uptake values were calculated by multiplying the yield inkg ha1 by the elemental in the dry forage
Surface soil samples (0ndash15 cm) were taken from both experiments atinitiation and analyzed for organic carbon using dry combustion[16] Inspring 2001 bulk density samples were taken with a Giddings soil probefrom the experimental area and an adjacent area that was conventionallytilled for comparison Also in spring 2001 surface soil samples (0ndash15 cm)samples were taken between plant crowns to simulate the initial samplingand also from within the crown of the plant to evaluate samplingmethods Soil organic carbon levels (mgC cm2) were calculated as
1202 Thomason et al
ORDER REPRINTS
a product of bulk density (g soil cm3) core depth (cm) and soil carbonconcentration (mgCg1 soil)
Statistical evaluation and analysis of variance were performedusing SAS[19]
RESULTS
Chickasha
The Chickasha site was the only one established in time for the 1997summer harvests Central Oklahoma received timely and adequaterainfall throughout the summer and maximum production levels werein excess of 30Mgha1 (Table 3) Three harvests one early in the
Table 1 Treatment structure for switchgrass experiment Chickasha (initiated
1996) and Perkins (initiated 1998)
Trt N rate N application method of harvests
1 0 mdash One
2 0 mdash Two
3 0 mdash Three
4 112 All in April One
5 224 All in April One
6 448 All in April One
7 896 All in April One
8 112 All in April Two
9 224 All in April Two
10 448 All in April Two
11 896 All in April Two
12 112 All in April Three
13 224 All in April Three
14 448 All in April Three
15 896 All in April Three
16 112 12 in April 12 aft 1st harvest Two
17 224 12 in April 12 aft 1st harvest Two
18 448 12 in April 12 aft 1st harvest Two
19 896 12 in April 12 aft 1st harvest Two
20 112 13 in April 13 aft 1st harv 13 aft 2nd harv Three
21 224 13 in April 13 aft 1st harv 13 aft 2nd harv Three
22 448 13 in April 13 aft 1st harv 13 aft 2nd harv Three
23 896 13 in April 13 aft 1st harv 13 aft 2nd harv Three
Switchgrass Response to Applied Nitrogen 1203
ORDER REPRINTS
Table
2
Initialsoilchem
icalcharacteristics
(0ndash15cm
)andclassificationatChickashaandPerkinsOK
Location
pH
a
NH
4-N
NO
3-N
Pb
Kb
TotalN
cOrganic
Cc
Dbinitial
Db2001
(mgkg1)
(mgg1)
(gcm
3)
Chickasha
69
758
112
28
215
006
82
143
141
ClassificationDale
siltloam
(fine-siltymixedsuperactive
thermic
Pachic
Haplustoll)
Perkins
67
753
21
77
325
09
68
147
147
ClassificationTellersandyloam
(fine-loamymixedactive
thermic
Udic
Argiustoll)
Dbbulk
density
(gcm
3)
apH11
soilwater
bPandKMehlich
III
cOrganic
CandtotalNdry
combustion
1204 Thomason et al
ORDER REPRINTS
summer one in late summer and one at the end of the season producedmore biomass (277Mgha1) compared to one harvest at the end of theseason (186Mgha1) These results reflect the ideal weather conditionspresent in 1997 that resulted in high yields Three harvests resulted inhigher N uptake values than those with fewer cuttings even when yieldswere higher for plots with fewer cutting dates (Table 3) The lowest Nuptake values for any treatment occurred with lower N rates (less than224 kg ha1) and one or two cuttings Three harvests increased K uptakeby the plants and split-applying the N over three dates resulted in more Kuptake than with two N application dates Neither treatment removed asmuch K as those with all N applied in April This is plausible consideringthe amount of K removed in the stems Phosphorus uptake levels wereon average approximately ten times lower than N or K uptake levelsThis was expected based on previous work documenting NP ratios of101[20] Splitting N applications over two dates resulted in lower Premoval than when applying all N early in the season (Table 3)
In 1998 a significant response to applied N was observed Howeverno differences in harvest frequency were noted probably due to the lackof rainfall in mid-summer Total yields were much lower than in 1997Lower rates of early season N and the removal of forage in late-summerdecreased yields in plots with three harvests and three-way split Napplications when compared to those cut twice Although yields werelower in 1998 maximum N uptake was higher than 1997 (375 and330 kg ha1 respectively) There was no difference in N uptake untiltotal N rates reached 224 kg ha1 Potassium uptake values were foundto follow the same trend as N Maximum K uptake occurred withthree-harvests and lowest values with one-harvest (Table 4)
Yields were again high at the Chickasha site in 1999 with some plotsproducing over 20Mgha1 (Table 5) The average yield for the site was17Mgha1 The highest levels of N uptake were observed with splitapplications of N and multiple harvests Uptake of K mirrored that forN in that number of harvests was highly significant and multipleharvests tended to remove more K than one harvest Phosphorus uptakewas greatest for three harvests regardless of N timing (353 and154 kg ha1 for three and one harvest respectively)
Yields for 2000 represent only the first two scheduled harvests for theyear and not the final end of season harvest Due to heavy fall rainsharvest was delayed and due to lack of communication the area wasburned before the final harvest could be taken Therefore yields shown inTable 6 represent the sum of only two cuttings The highest yields werecut two times (scheduled for three) and either not fertilized or fertilizedat the lowest rate of 112 kgNha1 (154 and 157Mgha1) Nitrogen
Switchgrass Response to Applied Nitrogen 1205
ORDER REPRINTS
Table
3
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1997
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
238501
10941
28072
258
441
1491
191
Cutting
24132329
b709443
b1344882
b6236
b9809
11234
b4789
b
Ntiming
3361873
10535
37908
134
30
19
58
Nrate
31564708
a209208
a171088
a15333
2605
2557
534
a
CuttingaN
rate
8707859
56216
26387
393
1526
2166
302
NtimingaN
rate
6651074
41644
60091
527
1232
2031
314
Residualerror
44
478953
38207
52088
473
1924
1917
288
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
222
1650
1689
195
386
400
131
112
1harvest
174
1177
1247
134
337
372
104
224
1harvest
164
1406
1285
154
284
310
100
448
1harvest
169
1186
1311
135
322
352
105
896
1harvest
203
1541
1489
173
394
390
127
02harvests
334
2548
2612
296
552
600
208
112
2harvests
155
1536
1521
161
403
344
118
1206 Thomason et al
ORDER REPRINTS
224
2harvests
337
2825
2694
284
643
688
222
448
2harvests
296
2830
2842
310
531
589
206
896
2harvests
244
2311
2337
217
403
464
163
03harvests
267
2325
3136
267
520
594
182
112
3harvests
249
2151
2902
244
348
389
193
224
3harvests
277
2608
3358
293
420
432
237
448
3harvests
309
3000
3814
333
425
473
265
896
3harvests
286
3202
3275
268
420
449
250
112
2-spN2harv
241
2037
1976
216
420
490
160
224
2-spN2harv
253
2091
1958
219
482
492
162
448
2-spN2harv
367
3306
3413
382
626
691
243
896
2-spN2harv
202
1950
1714
212
416
424
148
112
3-spN3harv
247
2101
2677
237
354
416
220
224
3-spN3harv
199
1821
2191
202
322
342
164
448
3-spN3harv
318
2145
3687
325
490
485
251
896
3-spN3harv
291
2739
3411
313
433
469
254
SED
57
505
589
53
113
113
44
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1207
ORDER REPRINTS
Table
4
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2996539
a87600
205053
a636
9278
15536
1010
Cutting
2372035
414096
a653177
b1024
1009
1563
266
Ntiming
3576196
111018
185774
a936
4895
6344
804
Nrate
3811575
a33003
62676
a527
a4584
a5872
336
a
CuttingaN
rate
8239068
59376
64205
400
6028
10433
560
NtimingaN
rate
6168684
34597
43532
180
2624
7172
282
Residualerror
44
220581
50460
52109
412
3338
4005
318
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
166
2048
1902
221
689
592
180
112
1harvest
141
1780
1875
195
601
638
164
224
1harvest
158
2127
2119
207
698
668
183
448
1harvest
172
2170
2212
211
726
747
200
896
1harvest
100
1328
1256
117
434
430
114
02harvests
166
2232
2468
225
677
776
205
112
2harvests
112
1548
1610
169
436
438
124
224
2harvests
226
3000
3378
311
910
1046
277
1208 Thomason et al
ORDER REPRINTS
448
2harvests
147
1956
1855
187
309
300
98
896
2harvests
162
2265
2241
191
575
680
190
03harvests
215
3403
3473
280
671
819
228
112
3harvests
168
2352
2705
201
533
658
184
224
3harvests
205
2833
3432
253
616
716
205
448
3harvests
245
3756
3864
289
641
668
190
896
3harvests
147
2229
2377
189
487
537
165
112
2-spN2harv
175
2119
2455
247
614
757
213
224
2-spN2harv
200
2677
3123
289
777
846
258
448
2-spN2harv
158
2070
2464
212
601
725
200
896
2-spN2harv
156
2355
2207
220
621
609
201
112
3-spN3harv
141
1962
2110
164
425
522
140
224
3-spN3harv
146
2233
2228
183
520
567
169
448
3-spN3harv
175
2375
2739
219
531
619
172
896
3-spN3harv
135
2210
2376
172
463
534
162
SED
12
580
589
52
149
163
46
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1209
ORDER REPRINTS
Table
5
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2464423
865906
1102070
a13008
a1665
6961
a291
Cutting
245101
952918
a1038877
b14290
b139
209
2203
b
Ntiming
3120137
133208
134666
1091
3230
2274
789
a
Nrate
32430687
717517
596007
4215
1799
2500
102
CuttingaN
rate
8207490
28101
43658
250
4465
b4667
a380
NtimingaN
rate
62060595
493140
380903
3444
810
1207
159
Residualerror
44
1562737
391299
334675
3504
1491
1808
291
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
109
781
1011
124
328
380
93
112
1harvest
150
1577
1541
171
478
532
145
224
1harvest
162
1459
1954
189
436
581
131
448
1harvest
191
1800
2386
181
693
715
180
896
1harvest
114
1257
1095
104
345
363
98
02harvests
179
2278
2736
274
543
602
192
112
2harvests
132
1754
2237
211
416
432
149
224
2harvests
170
2210
2453
244
530
614
182
1210 Thomason et al
ORDER REPRINTS
448
2harvests
162
2172
2291
221
352
400
120
896
2harvests
173
2474
2514
216
534
584
180
03harvests
200
2750
3273
352
500
559
205
112
3harvests
185
3150
3450
379
533
515
249
224
3harvests
167
2787
3303
335
392
436
184
448
3harvests
191
3300
3491
368
480
530
207
896
3harvests
154
2857
3000
331
431
472
194
112
2-spN2harv
145
1794
2258
226
432
469
156
224
2-spN2harv
146
1808
2078
223
564
501
195
448
2-spN2harv
175
2181
2713
248
487
557
171
896
2-spN2harv
208
2702
3557
288
654
703
220
112
3-spN3harv
155
2220
2522
260
353
381
145
224
3-spN3harv
152
2501
2949
304
412
401
174
448
3-spN3harv
180
2707
3137
354
405
475
170
896
3-spN3harv
263
3328
3144
425
366
401
167
SED
102
1573
1494
153
100
110
38
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1211
ORDER REPRINTS
Table
6
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2194823
b35769
a23391
1497
b1151
2969
b240
a
Cutting
2325370
b727339
b1445641
b9451
b2978
b1602
769
b
Ntiming
318979
a10279
15723
60
663
380
28
Nrate
3131730
b13237
24928
765
344
1865
a124
CuttingaN
rate
874236
a32484
a29096
491
1268
a1213
105
NtimingaN
rate
629574
7762
26341
384
237
239
41
Residualerror
44
31244
8263
16602
157
352
385
52
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
mdashmdash
mdashmdash
mdashmdash
mdash
112
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
224
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
448
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
896
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
02harvests
140
1493
1923
217
320
439
132
112
2harvests
110
1252
1516
203
264
345
106
224
2harvests
125
1334
1942
193
277
418
109
1212 Thomason et al
ORDER REPRINTS
448
2harvests
117
1485
1232
185
264
361
114
896
2harvests
102
1509
1217
152
315
338
104
03harvests
154
2564
3177
317
389
481
171
112
3harvests
157
2560
3317
347
387
507
170
224
3harvests
141
2477
3183
336
376
434
177
448
3harvests
154
2719
3084
342
384
451
180
896
3harvests
92
1676
2012
170
218
258
110
112
2-spN2harv
103
1123
1262
167
225
319
97
224
2-spN2harv
125
1265
1468
192
282
404
108
448
2-spN2harv
107
1212
1350
185
232
353
98
896
2-spN2harv
106
1419
1490
164
260
325
101
112
3-spN3harv
139
2238
2762
280
346
418
154
224
3-spN3harv
120
2194
2474
268
281
361
145
448
3-spN3harv
144
2504
3053
336
338
441
178
896
3-spN3harv
112
2013
2427
259
253
297
134
SED
14
235
333
32
49
51
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1213
ORDER REPRINTS
uptake of 240 kgNha1 was highest for two harvests (scheduled for
three) and April fertilization (Table 6) Potassium uptake was highest
with multiple harvests The lack of the final harvest for this data set
severely limited interpretation
Perkins
Yields in 1998 were lower than those at Chickasha due to sandier
soil and less total rainfall Treatment combinations with two or three
harvests and split N applications produced the highest yields averaging
over 11Mgha1 Forage nitrogen concentration did not increase
with increasing yields as was the trend over all years (Fig 1) Potassium
uptake was maximized with two harvests and either one or two N
applications both averaging near 180 kgKha1 Uptake of P was
significantly affected by N rate and was greatest with one harvest and
one N application date at 174 kg ha1 (Table 7) Phosphorus uptake
decreased with multiple harvestsPerkins again produced much lower yields than Chickasha in 1999
and significant differences were noted due to number of harvests and N
timing (Table 8) Average yields were highest for the three harvests three-
way split N treatments (Table 8) Multiple harvests increased crop N
uptake over those with the same total N rates and one harvest Potassium
uptake was high for all multiple harvest plots In fact one harvest
0
05
1
15
2
25
3
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
KN
y = 00002x - 16581 R2= 07749
y = 5E-05x + 04825 R2= 02171
Figure 1 N and K concentrations with increasing dry biomass yields Chickasha
and Perkins (View this art in color at wwwdekkercom)
1214 Thomason et al
ORDER REPRINTS
removed little more than half of the K of two or three harvests (775 vs1552 kg ha1) Three harvests also resulted in increased P uptake
Dry matter yield in 2000 averaged over N rate was 133Mgha1
(Table 9) Nitrogen removal was maximized with three harvests andsplitting N into three applications (Table 9) There was a trend towardincreased N uptake with increasing harvest frequency and increasing Nrate Three harvests with N split into three increments resulted in 48more K uptake than two harvests and two N application dates (896 vs1844 kg ha1) The highest average P uptake was found for three harvestsand three-way split N applications (202 kg ha1) (Table 9)
Soil Carbon
Organic C data from in crown and between crown samples werecompared to organic C from initial samples from the area to determine ifchanges had occurred Bulk density measurements taken from theexperimental area did not differ from an adjacent area that wasconventionally tilled Initial samples indicated average soil organic C(SOC) for the site of 68 and 82mg g1 for Perkins and Chickasharespectively These results are possibly confounded by known spatialvariability in SOC reported by Raun et al[21] Contrast comparisons founda significant linear decrease in SOC with increasing N rates and twoharvests for the Chickasha crown sampling (Table 10) A significantquadratic increase was noted for Perkins in crown samples and asignificant quadratic decrease in SOC with increasing N rate was foundfor between crown samples at Chickasha Taken together there seem to beno obvious trends toward increasing or decreasing SOC at either site Thisis potentially influenced by the fact that aboveground biomass wasremoved from the site Garten and Wullschleger[22] have estimated that itmay take a decade of switchgrass production to sequester a significantmeasurable amount of soil carbon Given more time SOC may increasebut the short duration (3ndash5 yrs) of this study has provided no real evidencesupporting this increase in SOC especially in the lsquolsquobetween crownrsquorsquosamples
CONCLUSIONS
Overall forage K concentrations increased with increasing yieldwhile N concentrations were not affected (Fig 1) This suggests anincreased likelihood of obtaining a response to K rather than N in
Switchgrass Response to Applied Nitrogen 1215
ORDER REPRINTS
Table
7
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
273649
35478
70045
b2962
b18430
b2215
a151
Cutting
239889
137708
102599
b392
18
1398
56
Ntiming
31062
151319
7734
76
4818
105
14
Nrate
3118782
a202660
47764
157
a1925
1045
184
CuttingaN
rate
850489
92751
21729
a164
2875
1466
165
NtimingaN
rate
622391
217859
21916
189
3453
1344
161
Residualerror
44
28679
173477
12329
94
2004
620
112
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
106
1889
972
162
442
261
147
112
1harvest
84
1239
1058
136
577
268
124
224
1harvest
102
1812
1033
173
448
276
145
448
1harvest
119
1970
1530
177
535
326
166
896
1harvest
104
2349
1840
222
522
323
178
02harvests
87
1110
1283
112
330
257
110
112
2harvests
103
1596
1662
139
534
350
147
1216 Thomason et al
ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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true if removal as in haying and not grazing is practiced Mineralcontent of switchgrass has been found to be higher on a percentage scalewith lower yields for the macronutrients N P K and calcium (Ca) Nochange in concentration for many micronutrients has been noted butconcentrations of boron (B) and manganese (Mn) have been found toincrease with increasing yields[3] Increases in plant N concentration withincreased applied N throughout the season have been noted[4] Staleyet al[5] found increasing N concentration in harvested plant parts withincreases in applied nitrogen They also found increased N uptake withincreased N rates but only in a one-harvest system Using 15N as a tracerthey attributed only 15ndash39 of total N uptake to fertilizer sources butthese uptake levels were still above those of tall fescue grown on the samemarginal sites Researchers in Pennsylvania have found N recoveries of40 of that applied and noted that this number was thought to decreaseas native soil N levels increased Measured on a daily basis switchgrasshas been found to take up 149ndash263 kgNha1 d1[6] Other researchstates that if water is not limiting then N levels account for 80 of thevariation in yields When water is limiting however the absence ofmoisture is the most important factor in yield determination[7] Depth ofsoil has been found to have little effect on N uptake[8]
Harvesting methods involving one to two cuttings each season havebeen shown to produce optimum yields in most systems[9] The earlierharvest is usually much higher in animal feed value and a two-cut systemmay allow early cuttings to be used as livestock feed and later cuttings forbiofuel production[10] Sanderson[11] found that as switchgrass maturesthrough the growing season stem components increase and leaf compo-nents decrease as a percent of total dry biomass This increase in stemportion is attributed to internode elongation necessary for plant growthand competitiveness
Switchgrass yields of 10ndash12Mgha1 have been reported inCanada[12] This led the authors to surmise that switchgrass could be avaluable source of biomass for biofuel production Hall et al[13] foundswitchgrass yields in Iowa to be near 6Mgha1 and noted a consistentresponse to added N up to 75 kgNha1
Bransby et al[14] noted switchgrass environmental benefits as an Nbuffer strip crop and as a net fixer of carbon (C) They state that the mostimportant benefit of using switchgrass as a fuel is the net cycling of C in theenvironment and give only slight importance to soil C sequestrationLong-term research in Alabama has recently shown no change in soilorganic C levels after 3 yrs in continuous switchgrass but after 10 yrs soilorganic C was 45 higher than adjacent fallow ground[15] The objectivesof this study were (1) to evaluate the response in biomass yield and uptake
Switchgrass Response to Applied Nitrogen 1201
ORDER REPRINTS
of N K P Ca Mg and S of switchgrass grown in Oklahoma to harvestfrequency and time and rate of applied nitrogen and (2) to evaluate theshort term effects of switchgrass production on soil organic C levels
MATERIALS AND METHODS
Two field experiments were initiated to evaluate switchgrass responseto applied N at rates of 0 112 224 448 and 896 kg ha1 In additionharvest frequency (once at the end of September twice mid-July andSeptember and three times May mid-July and September) and time ofN application (all in April 12 in April and 12 following first harvestand 13 in April 13 following first harvest and 13 following secondharvest) were evaluated (Table 1) Experiments were initiated atChickasha (Dale silt loam fine-silty mixed superactive thermic PachicHaplustoll) and Perkins (Teller sandy loam fine-loamy mixed thermicUdic Arguistoll) OK in 1996 and 1998 respectively Pre-establishmentsoil test values and soil classifications for the sites are reported in Table 2A randomized complete block design with three replications was used atboth locations with an incomplete factorial arrangement of treatments(Table 1) The northern lowland switchgrass variety lsquolsquoKanlowrsquorsquo wasbroadcast seeded in 1996 at Chickasha and 1998 at Perkins at a rate of11 kg pure live seed ha1 The stand at Chickasha was allowed a one-yearestablishment phase and harvesting began the following spring whilePerkins was planted and harvesting begun in the same year At both sitespreplant rates of 112 kgNha1 224 kg P2O5 ha
1 and 560 kgK2Oha1
were applied to the entire area Switchgrass was harvested at a heightof 10ndash15 cm using a lsquolsquoCarterrsquorsquo harvester
Forage samples were dried and ground to pass a 140-mesh sieve(100 um) and analyzed for total N content using a Carlo-Erba NA 1500automated dry combustion analyzer[16] Forage samples were alsoanalyzed for tissue concentrations of P K[17] Ca Mg and S[18]
Nutrient uptake values were calculated by multiplying the yield inkg ha1 by the elemental in the dry forage
Surface soil samples (0ndash15 cm) were taken from both experiments atinitiation and analyzed for organic carbon using dry combustion[16] Inspring 2001 bulk density samples were taken with a Giddings soil probefrom the experimental area and an adjacent area that was conventionallytilled for comparison Also in spring 2001 surface soil samples (0ndash15 cm)samples were taken between plant crowns to simulate the initial samplingand also from within the crown of the plant to evaluate samplingmethods Soil organic carbon levels (mgC cm2) were calculated as
1202 Thomason et al
ORDER REPRINTS
a product of bulk density (g soil cm3) core depth (cm) and soil carbonconcentration (mgCg1 soil)
Statistical evaluation and analysis of variance were performedusing SAS[19]
RESULTS
Chickasha
The Chickasha site was the only one established in time for the 1997summer harvests Central Oklahoma received timely and adequaterainfall throughout the summer and maximum production levels werein excess of 30Mgha1 (Table 3) Three harvests one early in the
Table 1 Treatment structure for switchgrass experiment Chickasha (initiated
1996) and Perkins (initiated 1998)
Trt N rate N application method of harvests
1 0 mdash One
2 0 mdash Two
3 0 mdash Three
4 112 All in April One
5 224 All in April One
6 448 All in April One
7 896 All in April One
8 112 All in April Two
9 224 All in April Two
10 448 All in April Two
11 896 All in April Two
12 112 All in April Three
13 224 All in April Three
14 448 All in April Three
15 896 All in April Three
16 112 12 in April 12 aft 1st harvest Two
17 224 12 in April 12 aft 1st harvest Two
18 448 12 in April 12 aft 1st harvest Two
19 896 12 in April 12 aft 1st harvest Two
20 112 13 in April 13 aft 1st harv 13 aft 2nd harv Three
21 224 13 in April 13 aft 1st harv 13 aft 2nd harv Three
22 448 13 in April 13 aft 1st harv 13 aft 2nd harv Three
23 896 13 in April 13 aft 1st harv 13 aft 2nd harv Three
Switchgrass Response to Applied Nitrogen 1203
ORDER REPRINTS
Table
2
Initialsoilchem
icalcharacteristics
(0ndash15cm
)andclassificationatChickashaandPerkinsOK
Location
pH
a
NH
4-N
NO
3-N
Pb
Kb
TotalN
cOrganic
Cc
Dbinitial
Db2001
(mgkg1)
(mgg1)
(gcm
3)
Chickasha
69
758
112
28
215
006
82
143
141
ClassificationDale
siltloam
(fine-siltymixedsuperactive
thermic
Pachic
Haplustoll)
Perkins
67
753
21
77
325
09
68
147
147
ClassificationTellersandyloam
(fine-loamymixedactive
thermic
Udic
Argiustoll)
Dbbulk
density
(gcm
3)
apH11
soilwater
bPandKMehlich
III
cOrganic
CandtotalNdry
combustion
1204 Thomason et al
ORDER REPRINTS
summer one in late summer and one at the end of the season producedmore biomass (277Mgha1) compared to one harvest at the end of theseason (186Mgha1) These results reflect the ideal weather conditionspresent in 1997 that resulted in high yields Three harvests resulted inhigher N uptake values than those with fewer cuttings even when yieldswere higher for plots with fewer cutting dates (Table 3) The lowest Nuptake values for any treatment occurred with lower N rates (less than224 kg ha1) and one or two cuttings Three harvests increased K uptakeby the plants and split-applying the N over three dates resulted in more Kuptake than with two N application dates Neither treatment removed asmuch K as those with all N applied in April This is plausible consideringthe amount of K removed in the stems Phosphorus uptake levels wereon average approximately ten times lower than N or K uptake levelsThis was expected based on previous work documenting NP ratios of101[20] Splitting N applications over two dates resulted in lower Premoval than when applying all N early in the season (Table 3)
In 1998 a significant response to applied N was observed Howeverno differences in harvest frequency were noted probably due to the lackof rainfall in mid-summer Total yields were much lower than in 1997Lower rates of early season N and the removal of forage in late-summerdecreased yields in plots with three harvests and three-way split Napplications when compared to those cut twice Although yields werelower in 1998 maximum N uptake was higher than 1997 (375 and330 kg ha1 respectively) There was no difference in N uptake untiltotal N rates reached 224 kg ha1 Potassium uptake values were foundto follow the same trend as N Maximum K uptake occurred withthree-harvests and lowest values with one-harvest (Table 4)
Yields were again high at the Chickasha site in 1999 with some plotsproducing over 20Mgha1 (Table 5) The average yield for the site was17Mgha1 The highest levels of N uptake were observed with splitapplications of N and multiple harvests Uptake of K mirrored that forN in that number of harvests was highly significant and multipleharvests tended to remove more K than one harvest Phosphorus uptakewas greatest for three harvests regardless of N timing (353 and154 kg ha1 for three and one harvest respectively)
Yields for 2000 represent only the first two scheduled harvests for theyear and not the final end of season harvest Due to heavy fall rainsharvest was delayed and due to lack of communication the area wasburned before the final harvest could be taken Therefore yields shown inTable 6 represent the sum of only two cuttings The highest yields werecut two times (scheduled for three) and either not fertilized or fertilizedat the lowest rate of 112 kgNha1 (154 and 157Mgha1) Nitrogen
Switchgrass Response to Applied Nitrogen 1205
ORDER REPRINTS
Table
3
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1997
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
238501
10941
28072
258
441
1491
191
Cutting
24132329
b709443
b1344882
b6236
b9809
11234
b4789
b
Ntiming
3361873
10535
37908
134
30
19
58
Nrate
31564708
a209208
a171088
a15333
2605
2557
534
a
CuttingaN
rate
8707859
56216
26387
393
1526
2166
302
NtimingaN
rate
6651074
41644
60091
527
1232
2031
314
Residualerror
44
478953
38207
52088
473
1924
1917
288
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
222
1650
1689
195
386
400
131
112
1harvest
174
1177
1247
134
337
372
104
224
1harvest
164
1406
1285
154
284
310
100
448
1harvest
169
1186
1311
135
322
352
105
896
1harvest
203
1541
1489
173
394
390
127
02harvests
334
2548
2612
296
552
600
208
112
2harvests
155
1536
1521
161
403
344
118
1206 Thomason et al
ORDER REPRINTS
224
2harvests
337
2825
2694
284
643
688
222
448
2harvests
296
2830
2842
310
531
589
206
896
2harvests
244
2311
2337
217
403
464
163
03harvests
267
2325
3136
267
520
594
182
112
3harvests
249
2151
2902
244
348
389
193
224
3harvests
277
2608
3358
293
420
432
237
448
3harvests
309
3000
3814
333
425
473
265
896
3harvests
286
3202
3275
268
420
449
250
112
2-spN2harv
241
2037
1976
216
420
490
160
224
2-spN2harv
253
2091
1958
219
482
492
162
448
2-spN2harv
367
3306
3413
382
626
691
243
896
2-spN2harv
202
1950
1714
212
416
424
148
112
3-spN3harv
247
2101
2677
237
354
416
220
224
3-spN3harv
199
1821
2191
202
322
342
164
448
3-spN3harv
318
2145
3687
325
490
485
251
896
3-spN3harv
291
2739
3411
313
433
469
254
SED
57
505
589
53
113
113
44
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1207
ORDER REPRINTS
Table
4
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2996539
a87600
205053
a636
9278
15536
1010
Cutting
2372035
414096
a653177
b1024
1009
1563
266
Ntiming
3576196
111018
185774
a936
4895
6344
804
Nrate
3811575
a33003
62676
a527
a4584
a5872
336
a
CuttingaN
rate
8239068
59376
64205
400
6028
10433
560
NtimingaN
rate
6168684
34597
43532
180
2624
7172
282
Residualerror
44
220581
50460
52109
412
3338
4005
318
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
166
2048
1902
221
689
592
180
112
1harvest
141
1780
1875
195
601
638
164
224
1harvest
158
2127
2119
207
698
668
183
448
1harvest
172
2170
2212
211
726
747
200
896
1harvest
100
1328
1256
117
434
430
114
02harvests
166
2232
2468
225
677
776
205
112
2harvests
112
1548
1610
169
436
438
124
224
2harvests
226
3000
3378
311
910
1046
277
1208 Thomason et al
ORDER REPRINTS
448
2harvests
147
1956
1855
187
309
300
98
896
2harvests
162
2265
2241
191
575
680
190
03harvests
215
3403
3473
280
671
819
228
112
3harvests
168
2352
2705
201
533
658
184
224
3harvests
205
2833
3432
253
616
716
205
448
3harvests
245
3756
3864
289
641
668
190
896
3harvests
147
2229
2377
189
487
537
165
112
2-spN2harv
175
2119
2455
247
614
757
213
224
2-spN2harv
200
2677
3123
289
777
846
258
448
2-spN2harv
158
2070
2464
212
601
725
200
896
2-spN2harv
156
2355
2207
220
621
609
201
112
3-spN3harv
141
1962
2110
164
425
522
140
224
3-spN3harv
146
2233
2228
183
520
567
169
448
3-spN3harv
175
2375
2739
219
531
619
172
896
3-spN3harv
135
2210
2376
172
463
534
162
SED
12
580
589
52
149
163
46
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1209
ORDER REPRINTS
Table
5
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2464423
865906
1102070
a13008
a1665
6961
a291
Cutting
245101
952918
a1038877
b14290
b139
209
2203
b
Ntiming
3120137
133208
134666
1091
3230
2274
789
a
Nrate
32430687
717517
596007
4215
1799
2500
102
CuttingaN
rate
8207490
28101
43658
250
4465
b4667
a380
NtimingaN
rate
62060595
493140
380903
3444
810
1207
159
Residualerror
44
1562737
391299
334675
3504
1491
1808
291
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
109
781
1011
124
328
380
93
112
1harvest
150
1577
1541
171
478
532
145
224
1harvest
162
1459
1954
189
436
581
131
448
1harvest
191
1800
2386
181
693
715
180
896
1harvest
114
1257
1095
104
345
363
98
02harvests
179
2278
2736
274
543
602
192
112
2harvests
132
1754
2237
211
416
432
149
224
2harvests
170
2210
2453
244
530
614
182
1210 Thomason et al
ORDER REPRINTS
448
2harvests
162
2172
2291
221
352
400
120
896
2harvests
173
2474
2514
216
534
584
180
03harvests
200
2750
3273
352
500
559
205
112
3harvests
185
3150
3450
379
533
515
249
224
3harvests
167
2787
3303
335
392
436
184
448
3harvests
191
3300
3491
368
480
530
207
896
3harvests
154
2857
3000
331
431
472
194
112
2-spN2harv
145
1794
2258
226
432
469
156
224
2-spN2harv
146
1808
2078
223
564
501
195
448
2-spN2harv
175
2181
2713
248
487
557
171
896
2-spN2harv
208
2702
3557
288
654
703
220
112
3-spN3harv
155
2220
2522
260
353
381
145
224
3-spN3harv
152
2501
2949
304
412
401
174
448
3-spN3harv
180
2707
3137
354
405
475
170
896
3-spN3harv
263
3328
3144
425
366
401
167
SED
102
1573
1494
153
100
110
38
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1211
ORDER REPRINTS
Table
6
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2194823
b35769
a23391
1497
b1151
2969
b240
a
Cutting
2325370
b727339
b1445641
b9451
b2978
b1602
769
b
Ntiming
318979
a10279
15723
60
663
380
28
Nrate
3131730
b13237
24928
765
344
1865
a124
CuttingaN
rate
874236
a32484
a29096
491
1268
a1213
105
NtimingaN
rate
629574
7762
26341
384
237
239
41
Residualerror
44
31244
8263
16602
157
352
385
52
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
mdashmdash
mdashmdash
mdashmdash
mdash
112
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
224
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
448
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
896
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
02harvests
140
1493
1923
217
320
439
132
112
2harvests
110
1252
1516
203
264
345
106
224
2harvests
125
1334
1942
193
277
418
109
1212 Thomason et al
ORDER REPRINTS
448
2harvests
117
1485
1232
185
264
361
114
896
2harvests
102
1509
1217
152
315
338
104
03harvests
154
2564
3177
317
389
481
171
112
3harvests
157
2560
3317
347
387
507
170
224
3harvests
141
2477
3183
336
376
434
177
448
3harvests
154
2719
3084
342
384
451
180
896
3harvests
92
1676
2012
170
218
258
110
112
2-spN2harv
103
1123
1262
167
225
319
97
224
2-spN2harv
125
1265
1468
192
282
404
108
448
2-spN2harv
107
1212
1350
185
232
353
98
896
2-spN2harv
106
1419
1490
164
260
325
101
112
3-spN3harv
139
2238
2762
280
346
418
154
224
3-spN3harv
120
2194
2474
268
281
361
145
448
3-spN3harv
144
2504
3053
336
338
441
178
896
3-spN3harv
112
2013
2427
259
253
297
134
SED
14
235
333
32
49
51
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1213
ORDER REPRINTS
uptake of 240 kgNha1 was highest for two harvests (scheduled for
three) and April fertilization (Table 6) Potassium uptake was highest
with multiple harvests The lack of the final harvest for this data set
severely limited interpretation
Perkins
Yields in 1998 were lower than those at Chickasha due to sandier
soil and less total rainfall Treatment combinations with two or three
harvests and split N applications produced the highest yields averaging
over 11Mgha1 Forage nitrogen concentration did not increase
with increasing yields as was the trend over all years (Fig 1) Potassium
uptake was maximized with two harvests and either one or two N
applications both averaging near 180 kgKha1 Uptake of P was
significantly affected by N rate and was greatest with one harvest and
one N application date at 174 kg ha1 (Table 7) Phosphorus uptake
decreased with multiple harvestsPerkins again produced much lower yields than Chickasha in 1999
and significant differences were noted due to number of harvests and N
timing (Table 8) Average yields were highest for the three harvests three-
way split N treatments (Table 8) Multiple harvests increased crop N
uptake over those with the same total N rates and one harvest Potassium
uptake was high for all multiple harvest plots In fact one harvest
0
05
1
15
2
25
3
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
KN
y = 00002x - 16581 R2= 07749
y = 5E-05x + 04825 R2= 02171
Figure 1 N and K concentrations with increasing dry biomass yields Chickasha
and Perkins (View this art in color at wwwdekkercom)
1214 Thomason et al
ORDER REPRINTS
removed little more than half of the K of two or three harvests (775 vs1552 kg ha1) Three harvests also resulted in increased P uptake
Dry matter yield in 2000 averaged over N rate was 133Mgha1
(Table 9) Nitrogen removal was maximized with three harvests andsplitting N into three applications (Table 9) There was a trend towardincreased N uptake with increasing harvest frequency and increasing Nrate Three harvests with N split into three increments resulted in 48more K uptake than two harvests and two N application dates (896 vs1844 kg ha1) The highest average P uptake was found for three harvestsand three-way split N applications (202 kg ha1) (Table 9)
Soil Carbon
Organic C data from in crown and between crown samples werecompared to organic C from initial samples from the area to determine ifchanges had occurred Bulk density measurements taken from theexperimental area did not differ from an adjacent area that wasconventionally tilled Initial samples indicated average soil organic C(SOC) for the site of 68 and 82mg g1 for Perkins and Chickasharespectively These results are possibly confounded by known spatialvariability in SOC reported by Raun et al[21] Contrast comparisons founda significant linear decrease in SOC with increasing N rates and twoharvests for the Chickasha crown sampling (Table 10) A significantquadratic increase was noted for Perkins in crown samples and asignificant quadratic decrease in SOC with increasing N rate was foundfor between crown samples at Chickasha Taken together there seem to beno obvious trends toward increasing or decreasing SOC at either site Thisis potentially influenced by the fact that aboveground biomass wasremoved from the site Garten and Wullschleger[22] have estimated that itmay take a decade of switchgrass production to sequester a significantmeasurable amount of soil carbon Given more time SOC may increasebut the short duration (3ndash5 yrs) of this study has provided no real evidencesupporting this increase in SOC especially in the lsquolsquobetween crownrsquorsquosamples
CONCLUSIONS
Overall forage K concentrations increased with increasing yieldwhile N concentrations were not affected (Fig 1) This suggests anincreased likelihood of obtaining a response to K rather than N in
Switchgrass Response to Applied Nitrogen 1215
ORDER REPRINTS
Table
7
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
273649
35478
70045
b2962
b18430
b2215
a151
Cutting
239889
137708
102599
b392
18
1398
56
Ntiming
31062
151319
7734
76
4818
105
14
Nrate
3118782
a202660
47764
157
a1925
1045
184
CuttingaN
rate
850489
92751
21729
a164
2875
1466
165
NtimingaN
rate
622391
217859
21916
189
3453
1344
161
Residualerror
44
28679
173477
12329
94
2004
620
112
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
106
1889
972
162
442
261
147
112
1harvest
84
1239
1058
136
577
268
124
224
1harvest
102
1812
1033
173
448
276
145
448
1harvest
119
1970
1530
177
535
326
166
896
1harvest
104
2349
1840
222
522
323
178
02harvests
87
1110
1283
112
330
257
110
112
2harvests
103
1596
1662
139
534
350
147
1216 Thomason et al
ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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of N K P Ca Mg and S of switchgrass grown in Oklahoma to harvestfrequency and time and rate of applied nitrogen and (2) to evaluate theshort term effects of switchgrass production on soil organic C levels
MATERIALS AND METHODS
Two field experiments were initiated to evaluate switchgrass responseto applied N at rates of 0 112 224 448 and 896 kg ha1 In additionharvest frequency (once at the end of September twice mid-July andSeptember and three times May mid-July and September) and time ofN application (all in April 12 in April and 12 following first harvestand 13 in April 13 following first harvest and 13 following secondharvest) were evaluated (Table 1) Experiments were initiated atChickasha (Dale silt loam fine-silty mixed superactive thermic PachicHaplustoll) and Perkins (Teller sandy loam fine-loamy mixed thermicUdic Arguistoll) OK in 1996 and 1998 respectively Pre-establishmentsoil test values and soil classifications for the sites are reported in Table 2A randomized complete block design with three replications was used atboth locations with an incomplete factorial arrangement of treatments(Table 1) The northern lowland switchgrass variety lsquolsquoKanlowrsquorsquo wasbroadcast seeded in 1996 at Chickasha and 1998 at Perkins at a rate of11 kg pure live seed ha1 The stand at Chickasha was allowed a one-yearestablishment phase and harvesting began the following spring whilePerkins was planted and harvesting begun in the same year At both sitespreplant rates of 112 kgNha1 224 kg P2O5 ha
1 and 560 kgK2Oha1
were applied to the entire area Switchgrass was harvested at a heightof 10ndash15 cm using a lsquolsquoCarterrsquorsquo harvester
Forage samples were dried and ground to pass a 140-mesh sieve(100 um) and analyzed for total N content using a Carlo-Erba NA 1500automated dry combustion analyzer[16] Forage samples were alsoanalyzed for tissue concentrations of P K[17] Ca Mg and S[18]
Nutrient uptake values were calculated by multiplying the yield inkg ha1 by the elemental in the dry forage
Surface soil samples (0ndash15 cm) were taken from both experiments atinitiation and analyzed for organic carbon using dry combustion[16] Inspring 2001 bulk density samples were taken with a Giddings soil probefrom the experimental area and an adjacent area that was conventionallytilled for comparison Also in spring 2001 surface soil samples (0ndash15 cm)samples were taken between plant crowns to simulate the initial samplingand also from within the crown of the plant to evaluate samplingmethods Soil organic carbon levels (mgC cm2) were calculated as
1202 Thomason et al
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a product of bulk density (g soil cm3) core depth (cm) and soil carbonconcentration (mgCg1 soil)
Statistical evaluation and analysis of variance were performedusing SAS[19]
RESULTS
Chickasha
The Chickasha site was the only one established in time for the 1997summer harvests Central Oklahoma received timely and adequaterainfall throughout the summer and maximum production levels werein excess of 30Mgha1 (Table 3) Three harvests one early in the
Table 1 Treatment structure for switchgrass experiment Chickasha (initiated
1996) and Perkins (initiated 1998)
Trt N rate N application method of harvests
1 0 mdash One
2 0 mdash Two
3 0 mdash Three
4 112 All in April One
5 224 All in April One
6 448 All in April One
7 896 All in April One
8 112 All in April Two
9 224 All in April Two
10 448 All in April Two
11 896 All in April Two
12 112 All in April Three
13 224 All in April Three
14 448 All in April Three
15 896 All in April Three
16 112 12 in April 12 aft 1st harvest Two
17 224 12 in April 12 aft 1st harvest Two
18 448 12 in April 12 aft 1st harvest Two
19 896 12 in April 12 aft 1st harvest Two
20 112 13 in April 13 aft 1st harv 13 aft 2nd harv Three
21 224 13 in April 13 aft 1st harv 13 aft 2nd harv Three
22 448 13 in April 13 aft 1st harv 13 aft 2nd harv Three
23 896 13 in April 13 aft 1st harv 13 aft 2nd harv Three
Switchgrass Response to Applied Nitrogen 1203
ORDER REPRINTS
Table
2
Initialsoilchem
icalcharacteristics
(0ndash15cm
)andclassificationatChickashaandPerkinsOK
Location
pH
a
NH
4-N
NO
3-N
Pb
Kb
TotalN
cOrganic
Cc
Dbinitial
Db2001
(mgkg1)
(mgg1)
(gcm
3)
Chickasha
69
758
112
28
215
006
82
143
141
ClassificationDale
siltloam
(fine-siltymixedsuperactive
thermic
Pachic
Haplustoll)
Perkins
67
753
21
77
325
09
68
147
147
ClassificationTellersandyloam
(fine-loamymixedactive
thermic
Udic
Argiustoll)
Dbbulk
density
(gcm
3)
apH11
soilwater
bPandKMehlich
III
cOrganic
CandtotalNdry
combustion
1204 Thomason et al
ORDER REPRINTS
summer one in late summer and one at the end of the season producedmore biomass (277Mgha1) compared to one harvest at the end of theseason (186Mgha1) These results reflect the ideal weather conditionspresent in 1997 that resulted in high yields Three harvests resulted inhigher N uptake values than those with fewer cuttings even when yieldswere higher for plots with fewer cutting dates (Table 3) The lowest Nuptake values for any treatment occurred with lower N rates (less than224 kg ha1) and one or two cuttings Three harvests increased K uptakeby the plants and split-applying the N over three dates resulted in more Kuptake than with two N application dates Neither treatment removed asmuch K as those with all N applied in April This is plausible consideringthe amount of K removed in the stems Phosphorus uptake levels wereon average approximately ten times lower than N or K uptake levelsThis was expected based on previous work documenting NP ratios of101[20] Splitting N applications over two dates resulted in lower Premoval than when applying all N early in the season (Table 3)
In 1998 a significant response to applied N was observed Howeverno differences in harvest frequency were noted probably due to the lackof rainfall in mid-summer Total yields were much lower than in 1997Lower rates of early season N and the removal of forage in late-summerdecreased yields in plots with three harvests and three-way split Napplications when compared to those cut twice Although yields werelower in 1998 maximum N uptake was higher than 1997 (375 and330 kg ha1 respectively) There was no difference in N uptake untiltotal N rates reached 224 kg ha1 Potassium uptake values were foundto follow the same trend as N Maximum K uptake occurred withthree-harvests and lowest values with one-harvest (Table 4)
Yields were again high at the Chickasha site in 1999 with some plotsproducing over 20Mgha1 (Table 5) The average yield for the site was17Mgha1 The highest levels of N uptake were observed with splitapplications of N and multiple harvests Uptake of K mirrored that forN in that number of harvests was highly significant and multipleharvests tended to remove more K than one harvest Phosphorus uptakewas greatest for three harvests regardless of N timing (353 and154 kg ha1 for three and one harvest respectively)
Yields for 2000 represent only the first two scheduled harvests for theyear and not the final end of season harvest Due to heavy fall rainsharvest was delayed and due to lack of communication the area wasburned before the final harvest could be taken Therefore yields shown inTable 6 represent the sum of only two cuttings The highest yields werecut two times (scheduled for three) and either not fertilized or fertilizedat the lowest rate of 112 kgNha1 (154 and 157Mgha1) Nitrogen
Switchgrass Response to Applied Nitrogen 1205
ORDER REPRINTS
Table
3
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1997
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
238501
10941
28072
258
441
1491
191
Cutting
24132329
b709443
b1344882
b6236
b9809
11234
b4789
b
Ntiming
3361873
10535
37908
134
30
19
58
Nrate
31564708
a209208
a171088
a15333
2605
2557
534
a
CuttingaN
rate
8707859
56216
26387
393
1526
2166
302
NtimingaN
rate
6651074
41644
60091
527
1232
2031
314
Residualerror
44
478953
38207
52088
473
1924
1917
288
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
222
1650
1689
195
386
400
131
112
1harvest
174
1177
1247
134
337
372
104
224
1harvest
164
1406
1285
154
284
310
100
448
1harvest
169
1186
1311
135
322
352
105
896
1harvest
203
1541
1489
173
394
390
127
02harvests
334
2548
2612
296
552
600
208
112
2harvests
155
1536
1521
161
403
344
118
1206 Thomason et al
ORDER REPRINTS
224
2harvests
337
2825
2694
284
643
688
222
448
2harvests
296
2830
2842
310
531
589
206
896
2harvests
244
2311
2337
217
403
464
163
03harvests
267
2325
3136
267
520
594
182
112
3harvests
249
2151
2902
244
348
389
193
224
3harvests
277
2608
3358
293
420
432
237
448
3harvests
309
3000
3814
333
425
473
265
896
3harvests
286
3202
3275
268
420
449
250
112
2-spN2harv
241
2037
1976
216
420
490
160
224
2-spN2harv
253
2091
1958
219
482
492
162
448
2-spN2harv
367
3306
3413
382
626
691
243
896
2-spN2harv
202
1950
1714
212
416
424
148
112
3-spN3harv
247
2101
2677
237
354
416
220
224
3-spN3harv
199
1821
2191
202
322
342
164
448
3-spN3harv
318
2145
3687
325
490
485
251
896
3-spN3harv
291
2739
3411
313
433
469
254
SED
57
505
589
53
113
113
44
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1207
ORDER REPRINTS
Table
4
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2996539
a87600
205053
a636
9278
15536
1010
Cutting
2372035
414096
a653177
b1024
1009
1563
266
Ntiming
3576196
111018
185774
a936
4895
6344
804
Nrate
3811575
a33003
62676
a527
a4584
a5872
336
a
CuttingaN
rate
8239068
59376
64205
400
6028
10433
560
NtimingaN
rate
6168684
34597
43532
180
2624
7172
282
Residualerror
44
220581
50460
52109
412
3338
4005
318
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
166
2048
1902
221
689
592
180
112
1harvest
141
1780
1875
195
601
638
164
224
1harvest
158
2127
2119
207
698
668
183
448
1harvest
172
2170
2212
211
726
747
200
896
1harvest
100
1328
1256
117
434
430
114
02harvests
166
2232
2468
225
677
776
205
112
2harvests
112
1548
1610
169
436
438
124
224
2harvests
226
3000
3378
311
910
1046
277
1208 Thomason et al
ORDER REPRINTS
448
2harvests
147
1956
1855
187
309
300
98
896
2harvests
162
2265
2241
191
575
680
190
03harvests
215
3403
3473
280
671
819
228
112
3harvests
168
2352
2705
201
533
658
184
224
3harvests
205
2833
3432
253
616
716
205
448
3harvests
245
3756
3864
289
641
668
190
896
3harvests
147
2229
2377
189
487
537
165
112
2-spN2harv
175
2119
2455
247
614
757
213
224
2-spN2harv
200
2677
3123
289
777
846
258
448
2-spN2harv
158
2070
2464
212
601
725
200
896
2-spN2harv
156
2355
2207
220
621
609
201
112
3-spN3harv
141
1962
2110
164
425
522
140
224
3-spN3harv
146
2233
2228
183
520
567
169
448
3-spN3harv
175
2375
2739
219
531
619
172
896
3-spN3harv
135
2210
2376
172
463
534
162
SED
12
580
589
52
149
163
46
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1209
ORDER REPRINTS
Table
5
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2464423
865906
1102070
a13008
a1665
6961
a291
Cutting
245101
952918
a1038877
b14290
b139
209
2203
b
Ntiming
3120137
133208
134666
1091
3230
2274
789
a
Nrate
32430687
717517
596007
4215
1799
2500
102
CuttingaN
rate
8207490
28101
43658
250
4465
b4667
a380
NtimingaN
rate
62060595
493140
380903
3444
810
1207
159
Residualerror
44
1562737
391299
334675
3504
1491
1808
291
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
109
781
1011
124
328
380
93
112
1harvest
150
1577
1541
171
478
532
145
224
1harvest
162
1459
1954
189
436
581
131
448
1harvest
191
1800
2386
181
693
715
180
896
1harvest
114
1257
1095
104
345
363
98
02harvests
179
2278
2736
274
543
602
192
112
2harvests
132
1754
2237
211
416
432
149
224
2harvests
170
2210
2453
244
530
614
182
1210 Thomason et al
ORDER REPRINTS
448
2harvests
162
2172
2291
221
352
400
120
896
2harvests
173
2474
2514
216
534
584
180
03harvests
200
2750
3273
352
500
559
205
112
3harvests
185
3150
3450
379
533
515
249
224
3harvests
167
2787
3303
335
392
436
184
448
3harvests
191
3300
3491
368
480
530
207
896
3harvests
154
2857
3000
331
431
472
194
112
2-spN2harv
145
1794
2258
226
432
469
156
224
2-spN2harv
146
1808
2078
223
564
501
195
448
2-spN2harv
175
2181
2713
248
487
557
171
896
2-spN2harv
208
2702
3557
288
654
703
220
112
3-spN3harv
155
2220
2522
260
353
381
145
224
3-spN3harv
152
2501
2949
304
412
401
174
448
3-spN3harv
180
2707
3137
354
405
475
170
896
3-spN3harv
263
3328
3144
425
366
401
167
SED
102
1573
1494
153
100
110
38
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1211
ORDER REPRINTS
Table
6
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2194823
b35769
a23391
1497
b1151
2969
b240
a
Cutting
2325370
b727339
b1445641
b9451
b2978
b1602
769
b
Ntiming
318979
a10279
15723
60
663
380
28
Nrate
3131730
b13237
24928
765
344
1865
a124
CuttingaN
rate
874236
a32484
a29096
491
1268
a1213
105
NtimingaN
rate
629574
7762
26341
384
237
239
41
Residualerror
44
31244
8263
16602
157
352
385
52
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
mdashmdash
mdashmdash
mdashmdash
mdash
112
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
224
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
448
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
896
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
02harvests
140
1493
1923
217
320
439
132
112
2harvests
110
1252
1516
203
264
345
106
224
2harvests
125
1334
1942
193
277
418
109
1212 Thomason et al
ORDER REPRINTS
448
2harvests
117
1485
1232
185
264
361
114
896
2harvests
102
1509
1217
152
315
338
104
03harvests
154
2564
3177
317
389
481
171
112
3harvests
157
2560
3317
347
387
507
170
224
3harvests
141
2477
3183
336
376
434
177
448
3harvests
154
2719
3084
342
384
451
180
896
3harvests
92
1676
2012
170
218
258
110
112
2-spN2harv
103
1123
1262
167
225
319
97
224
2-spN2harv
125
1265
1468
192
282
404
108
448
2-spN2harv
107
1212
1350
185
232
353
98
896
2-spN2harv
106
1419
1490
164
260
325
101
112
3-spN3harv
139
2238
2762
280
346
418
154
224
3-spN3harv
120
2194
2474
268
281
361
145
448
3-spN3harv
144
2504
3053
336
338
441
178
896
3-spN3harv
112
2013
2427
259
253
297
134
SED
14
235
333
32
49
51
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1213
ORDER REPRINTS
uptake of 240 kgNha1 was highest for two harvests (scheduled for
three) and April fertilization (Table 6) Potassium uptake was highest
with multiple harvests The lack of the final harvest for this data set
severely limited interpretation
Perkins
Yields in 1998 were lower than those at Chickasha due to sandier
soil and less total rainfall Treatment combinations with two or three
harvests and split N applications produced the highest yields averaging
over 11Mgha1 Forage nitrogen concentration did not increase
with increasing yields as was the trend over all years (Fig 1) Potassium
uptake was maximized with two harvests and either one or two N
applications both averaging near 180 kgKha1 Uptake of P was
significantly affected by N rate and was greatest with one harvest and
one N application date at 174 kg ha1 (Table 7) Phosphorus uptake
decreased with multiple harvestsPerkins again produced much lower yields than Chickasha in 1999
and significant differences were noted due to number of harvests and N
timing (Table 8) Average yields were highest for the three harvests three-
way split N treatments (Table 8) Multiple harvests increased crop N
uptake over those with the same total N rates and one harvest Potassium
uptake was high for all multiple harvest plots In fact one harvest
0
05
1
15
2
25
3
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
KN
y = 00002x - 16581 R2= 07749
y = 5E-05x + 04825 R2= 02171
Figure 1 N and K concentrations with increasing dry biomass yields Chickasha
and Perkins (View this art in color at wwwdekkercom)
1214 Thomason et al
ORDER REPRINTS
removed little more than half of the K of two or three harvests (775 vs1552 kg ha1) Three harvests also resulted in increased P uptake
Dry matter yield in 2000 averaged over N rate was 133Mgha1
(Table 9) Nitrogen removal was maximized with three harvests andsplitting N into three applications (Table 9) There was a trend towardincreased N uptake with increasing harvest frequency and increasing Nrate Three harvests with N split into three increments resulted in 48more K uptake than two harvests and two N application dates (896 vs1844 kg ha1) The highest average P uptake was found for three harvestsand three-way split N applications (202 kg ha1) (Table 9)
Soil Carbon
Organic C data from in crown and between crown samples werecompared to organic C from initial samples from the area to determine ifchanges had occurred Bulk density measurements taken from theexperimental area did not differ from an adjacent area that wasconventionally tilled Initial samples indicated average soil organic C(SOC) for the site of 68 and 82mg g1 for Perkins and Chickasharespectively These results are possibly confounded by known spatialvariability in SOC reported by Raun et al[21] Contrast comparisons founda significant linear decrease in SOC with increasing N rates and twoharvests for the Chickasha crown sampling (Table 10) A significantquadratic increase was noted for Perkins in crown samples and asignificant quadratic decrease in SOC with increasing N rate was foundfor between crown samples at Chickasha Taken together there seem to beno obvious trends toward increasing or decreasing SOC at either site Thisis potentially influenced by the fact that aboveground biomass wasremoved from the site Garten and Wullschleger[22] have estimated that itmay take a decade of switchgrass production to sequester a significantmeasurable amount of soil carbon Given more time SOC may increasebut the short duration (3ndash5 yrs) of this study has provided no real evidencesupporting this increase in SOC especially in the lsquolsquobetween crownrsquorsquosamples
CONCLUSIONS
Overall forage K concentrations increased with increasing yieldwhile N concentrations were not affected (Fig 1) This suggests anincreased likelihood of obtaining a response to K rather than N in
Switchgrass Response to Applied Nitrogen 1215
ORDER REPRINTS
Table
7
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
273649
35478
70045
b2962
b18430
b2215
a151
Cutting
239889
137708
102599
b392
18
1398
56
Ntiming
31062
151319
7734
76
4818
105
14
Nrate
3118782
a202660
47764
157
a1925
1045
184
CuttingaN
rate
850489
92751
21729
a164
2875
1466
165
NtimingaN
rate
622391
217859
21916
189
3453
1344
161
Residualerror
44
28679
173477
12329
94
2004
620
112
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
106
1889
972
162
442
261
147
112
1harvest
84
1239
1058
136
577
268
124
224
1harvest
102
1812
1033
173
448
276
145
448
1harvest
119
1970
1530
177
535
326
166
896
1harvest
104
2349
1840
222
522
323
178
02harvests
87
1110
1283
112
330
257
110
112
2harvests
103
1596
1662
139
534
350
147
1216 Thomason et al
ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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ORDER REPRINTS
a product of bulk density (g soil cm3) core depth (cm) and soil carbonconcentration (mgCg1 soil)
Statistical evaluation and analysis of variance were performedusing SAS[19]
RESULTS
Chickasha
The Chickasha site was the only one established in time for the 1997summer harvests Central Oklahoma received timely and adequaterainfall throughout the summer and maximum production levels werein excess of 30Mgha1 (Table 3) Three harvests one early in the
Table 1 Treatment structure for switchgrass experiment Chickasha (initiated
1996) and Perkins (initiated 1998)
Trt N rate N application method of harvests
1 0 mdash One
2 0 mdash Two
3 0 mdash Three
4 112 All in April One
5 224 All in April One
6 448 All in April One
7 896 All in April One
8 112 All in April Two
9 224 All in April Two
10 448 All in April Two
11 896 All in April Two
12 112 All in April Three
13 224 All in April Three
14 448 All in April Three
15 896 All in April Three
16 112 12 in April 12 aft 1st harvest Two
17 224 12 in April 12 aft 1st harvest Two
18 448 12 in April 12 aft 1st harvest Two
19 896 12 in April 12 aft 1st harvest Two
20 112 13 in April 13 aft 1st harv 13 aft 2nd harv Three
21 224 13 in April 13 aft 1st harv 13 aft 2nd harv Three
22 448 13 in April 13 aft 1st harv 13 aft 2nd harv Three
23 896 13 in April 13 aft 1st harv 13 aft 2nd harv Three
Switchgrass Response to Applied Nitrogen 1203
ORDER REPRINTS
Table
2
Initialsoilchem
icalcharacteristics
(0ndash15cm
)andclassificationatChickashaandPerkinsOK
Location
pH
a
NH
4-N
NO
3-N
Pb
Kb
TotalN
cOrganic
Cc
Dbinitial
Db2001
(mgkg1)
(mgg1)
(gcm
3)
Chickasha
69
758
112
28
215
006
82
143
141
ClassificationDale
siltloam
(fine-siltymixedsuperactive
thermic
Pachic
Haplustoll)
Perkins
67
753
21
77
325
09
68
147
147
ClassificationTellersandyloam
(fine-loamymixedactive
thermic
Udic
Argiustoll)
Dbbulk
density
(gcm
3)
apH11
soilwater
bPandKMehlich
III
cOrganic
CandtotalNdry
combustion
1204 Thomason et al
ORDER REPRINTS
summer one in late summer and one at the end of the season producedmore biomass (277Mgha1) compared to one harvest at the end of theseason (186Mgha1) These results reflect the ideal weather conditionspresent in 1997 that resulted in high yields Three harvests resulted inhigher N uptake values than those with fewer cuttings even when yieldswere higher for plots with fewer cutting dates (Table 3) The lowest Nuptake values for any treatment occurred with lower N rates (less than224 kg ha1) and one or two cuttings Three harvests increased K uptakeby the plants and split-applying the N over three dates resulted in more Kuptake than with two N application dates Neither treatment removed asmuch K as those with all N applied in April This is plausible consideringthe amount of K removed in the stems Phosphorus uptake levels wereon average approximately ten times lower than N or K uptake levelsThis was expected based on previous work documenting NP ratios of101[20] Splitting N applications over two dates resulted in lower Premoval than when applying all N early in the season (Table 3)
In 1998 a significant response to applied N was observed Howeverno differences in harvest frequency were noted probably due to the lackof rainfall in mid-summer Total yields were much lower than in 1997Lower rates of early season N and the removal of forage in late-summerdecreased yields in plots with three harvests and three-way split Napplications when compared to those cut twice Although yields werelower in 1998 maximum N uptake was higher than 1997 (375 and330 kg ha1 respectively) There was no difference in N uptake untiltotal N rates reached 224 kg ha1 Potassium uptake values were foundto follow the same trend as N Maximum K uptake occurred withthree-harvests and lowest values with one-harvest (Table 4)
Yields were again high at the Chickasha site in 1999 with some plotsproducing over 20Mgha1 (Table 5) The average yield for the site was17Mgha1 The highest levels of N uptake were observed with splitapplications of N and multiple harvests Uptake of K mirrored that forN in that number of harvests was highly significant and multipleharvests tended to remove more K than one harvest Phosphorus uptakewas greatest for three harvests regardless of N timing (353 and154 kg ha1 for three and one harvest respectively)
Yields for 2000 represent only the first two scheduled harvests for theyear and not the final end of season harvest Due to heavy fall rainsharvest was delayed and due to lack of communication the area wasburned before the final harvest could be taken Therefore yields shown inTable 6 represent the sum of only two cuttings The highest yields werecut two times (scheduled for three) and either not fertilized or fertilizedat the lowest rate of 112 kgNha1 (154 and 157Mgha1) Nitrogen
Switchgrass Response to Applied Nitrogen 1205
ORDER REPRINTS
Table
3
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1997
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
238501
10941
28072
258
441
1491
191
Cutting
24132329
b709443
b1344882
b6236
b9809
11234
b4789
b
Ntiming
3361873
10535
37908
134
30
19
58
Nrate
31564708
a209208
a171088
a15333
2605
2557
534
a
CuttingaN
rate
8707859
56216
26387
393
1526
2166
302
NtimingaN
rate
6651074
41644
60091
527
1232
2031
314
Residualerror
44
478953
38207
52088
473
1924
1917
288
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
222
1650
1689
195
386
400
131
112
1harvest
174
1177
1247
134
337
372
104
224
1harvest
164
1406
1285
154
284
310
100
448
1harvest
169
1186
1311
135
322
352
105
896
1harvest
203
1541
1489
173
394
390
127
02harvests
334
2548
2612
296
552
600
208
112
2harvests
155
1536
1521
161
403
344
118
1206 Thomason et al
ORDER REPRINTS
224
2harvests
337
2825
2694
284
643
688
222
448
2harvests
296
2830
2842
310
531
589
206
896
2harvests
244
2311
2337
217
403
464
163
03harvests
267
2325
3136
267
520
594
182
112
3harvests
249
2151
2902
244
348
389
193
224
3harvests
277
2608
3358
293
420
432
237
448
3harvests
309
3000
3814
333
425
473
265
896
3harvests
286
3202
3275
268
420
449
250
112
2-spN2harv
241
2037
1976
216
420
490
160
224
2-spN2harv
253
2091
1958
219
482
492
162
448
2-spN2harv
367
3306
3413
382
626
691
243
896
2-spN2harv
202
1950
1714
212
416
424
148
112
3-spN3harv
247
2101
2677
237
354
416
220
224
3-spN3harv
199
1821
2191
202
322
342
164
448
3-spN3harv
318
2145
3687
325
490
485
251
896
3-spN3harv
291
2739
3411
313
433
469
254
SED
57
505
589
53
113
113
44
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1207
ORDER REPRINTS
Table
4
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2996539
a87600
205053
a636
9278
15536
1010
Cutting
2372035
414096
a653177
b1024
1009
1563
266
Ntiming
3576196
111018
185774
a936
4895
6344
804
Nrate
3811575
a33003
62676
a527
a4584
a5872
336
a
CuttingaN
rate
8239068
59376
64205
400
6028
10433
560
NtimingaN
rate
6168684
34597
43532
180
2624
7172
282
Residualerror
44
220581
50460
52109
412
3338
4005
318
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
166
2048
1902
221
689
592
180
112
1harvest
141
1780
1875
195
601
638
164
224
1harvest
158
2127
2119
207
698
668
183
448
1harvest
172
2170
2212
211
726
747
200
896
1harvest
100
1328
1256
117
434
430
114
02harvests
166
2232
2468
225
677
776
205
112
2harvests
112
1548
1610
169
436
438
124
224
2harvests
226
3000
3378
311
910
1046
277
1208 Thomason et al
ORDER REPRINTS
448
2harvests
147
1956
1855
187
309
300
98
896
2harvests
162
2265
2241
191
575
680
190
03harvests
215
3403
3473
280
671
819
228
112
3harvests
168
2352
2705
201
533
658
184
224
3harvests
205
2833
3432
253
616
716
205
448
3harvests
245
3756
3864
289
641
668
190
896
3harvests
147
2229
2377
189
487
537
165
112
2-spN2harv
175
2119
2455
247
614
757
213
224
2-spN2harv
200
2677
3123
289
777
846
258
448
2-spN2harv
158
2070
2464
212
601
725
200
896
2-spN2harv
156
2355
2207
220
621
609
201
112
3-spN3harv
141
1962
2110
164
425
522
140
224
3-spN3harv
146
2233
2228
183
520
567
169
448
3-spN3harv
175
2375
2739
219
531
619
172
896
3-spN3harv
135
2210
2376
172
463
534
162
SED
12
580
589
52
149
163
46
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1209
ORDER REPRINTS
Table
5
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2464423
865906
1102070
a13008
a1665
6961
a291
Cutting
245101
952918
a1038877
b14290
b139
209
2203
b
Ntiming
3120137
133208
134666
1091
3230
2274
789
a
Nrate
32430687
717517
596007
4215
1799
2500
102
CuttingaN
rate
8207490
28101
43658
250
4465
b4667
a380
NtimingaN
rate
62060595
493140
380903
3444
810
1207
159
Residualerror
44
1562737
391299
334675
3504
1491
1808
291
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
109
781
1011
124
328
380
93
112
1harvest
150
1577
1541
171
478
532
145
224
1harvest
162
1459
1954
189
436
581
131
448
1harvest
191
1800
2386
181
693
715
180
896
1harvest
114
1257
1095
104
345
363
98
02harvests
179
2278
2736
274
543
602
192
112
2harvests
132
1754
2237
211
416
432
149
224
2harvests
170
2210
2453
244
530
614
182
1210 Thomason et al
ORDER REPRINTS
448
2harvests
162
2172
2291
221
352
400
120
896
2harvests
173
2474
2514
216
534
584
180
03harvests
200
2750
3273
352
500
559
205
112
3harvests
185
3150
3450
379
533
515
249
224
3harvests
167
2787
3303
335
392
436
184
448
3harvests
191
3300
3491
368
480
530
207
896
3harvests
154
2857
3000
331
431
472
194
112
2-spN2harv
145
1794
2258
226
432
469
156
224
2-spN2harv
146
1808
2078
223
564
501
195
448
2-spN2harv
175
2181
2713
248
487
557
171
896
2-spN2harv
208
2702
3557
288
654
703
220
112
3-spN3harv
155
2220
2522
260
353
381
145
224
3-spN3harv
152
2501
2949
304
412
401
174
448
3-spN3harv
180
2707
3137
354
405
475
170
896
3-spN3harv
263
3328
3144
425
366
401
167
SED
102
1573
1494
153
100
110
38
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1211
ORDER REPRINTS
Table
6
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2194823
b35769
a23391
1497
b1151
2969
b240
a
Cutting
2325370
b727339
b1445641
b9451
b2978
b1602
769
b
Ntiming
318979
a10279
15723
60
663
380
28
Nrate
3131730
b13237
24928
765
344
1865
a124
CuttingaN
rate
874236
a32484
a29096
491
1268
a1213
105
NtimingaN
rate
629574
7762
26341
384
237
239
41
Residualerror
44
31244
8263
16602
157
352
385
52
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
mdashmdash
mdashmdash
mdashmdash
mdash
112
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
224
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
448
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
896
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
02harvests
140
1493
1923
217
320
439
132
112
2harvests
110
1252
1516
203
264
345
106
224
2harvests
125
1334
1942
193
277
418
109
1212 Thomason et al
ORDER REPRINTS
448
2harvests
117
1485
1232
185
264
361
114
896
2harvests
102
1509
1217
152
315
338
104
03harvests
154
2564
3177
317
389
481
171
112
3harvests
157
2560
3317
347
387
507
170
224
3harvests
141
2477
3183
336
376
434
177
448
3harvests
154
2719
3084
342
384
451
180
896
3harvests
92
1676
2012
170
218
258
110
112
2-spN2harv
103
1123
1262
167
225
319
97
224
2-spN2harv
125
1265
1468
192
282
404
108
448
2-spN2harv
107
1212
1350
185
232
353
98
896
2-spN2harv
106
1419
1490
164
260
325
101
112
3-spN3harv
139
2238
2762
280
346
418
154
224
3-spN3harv
120
2194
2474
268
281
361
145
448
3-spN3harv
144
2504
3053
336
338
441
178
896
3-spN3harv
112
2013
2427
259
253
297
134
SED
14
235
333
32
49
51
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1213
ORDER REPRINTS
uptake of 240 kgNha1 was highest for two harvests (scheduled for
three) and April fertilization (Table 6) Potassium uptake was highest
with multiple harvests The lack of the final harvest for this data set
severely limited interpretation
Perkins
Yields in 1998 were lower than those at Chickasha due to sandier
soil and less total rainfall Treatment combinations with two or three
harvests and split N applications produced the highest yields averaging
over 11Mgha1 Forage nitrogen concentration did not increase
with increasing yields as was the trend over all years (Fig 1) Potassium
uptake was maximized with two harvests and either one or two N
applications both averaging near 180 kgKha1 Uptake of P was
significantly affected by N rate and was greatest with one harvest and
one N application date at 174 kg ha1 (Table 7) Phosphorus uptake
decreased with multiple harvestsPerkins again produced much lower yields than Chickasha in 1999
and significant differences were noted due to number of harvests and N
timing (Table 8) Average yields were highest for the three harvests three-
way split N treatments (Table 8) Multiple harvests increased crop N
uptake over those with the same total N rates and one harvest Potassium
uptake was high for all multiple harvest plots In fact one harvest
0
05
1
15
2
25
3
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
KN
y = 00002x - 16581 R2= 07749
y = 5E-05x + 04825 R2= 02171
Figure 1 N and K concentrations with increasing dry biomass yields Chickasha
and Perkins (View this art in color at wwwdekkercom)
1214 Thomason et al
ORDER REPRINTS
removed little more than half of the K of two or three harvests (775 vs1552 kg ha1) Three harvests also resulted in increased P uptake
Dry matter yield in 2000 averaged over N rate was 133Mgha1
(Table 9) Nitrogen removal was maximized with three harvests andsplitting N into three applications (Table 9) There was a trend towardincreased N uptake with increasing harvest frequency and increasing Nrate Three harvests with N split into three increments resulted in 48more K uptake than two harvests and two N application dates (896 vs1844 kg ha1) The highest average P uptake was found for three harvestsand three-way split N applications (202 kg ha1) (Table 9)
Soil Carbon
Organic C data from in crown and between crown samples werecompared to organic C from initial samples from the area to determine ifchanges had occurred Bulk density measurements taken from theexperimental area did not differ from an adjacent area that wasconventionally tilled Initial samples indicated average soil organic C(SOC) for the site of 68 and 82mg g1 for Perkins and Chickasharespectively These results are possibly confounded by known spatialvariability in SOC reported by Raun et al[21] Contrast comparisons founda significant linear decrease in SOC with increasing N rates and twoharvests for the Chickasha crown sampling (Table 10) A significantquadratic increase was noted for Perkins in crown samples and asignificant quadratic decrease in SOC with increasing N rate was foundfor between crown samples at Chickasha Taken together there seem to beno obvious trends toward increasing or decreasing SOC at either site Thisis potentially influenced by the fact that aboveground biomass wasremoved from the site Garten and Wullschleger[22] have estimated that itmay take a decade of switchgrass production to sequester a significantmeasurable amount of soil carbon Given more time SOC may increasebut the short duration (3ndash5 yrs) of this study has provided no real evidencesupporting this increase in SOC especially in the lsquolsquobetween crownrsquorsquosamples
CONCLUSIONS
Overall forage K concentrations increased with increasing yieldwhile N concentrations were not affected (Fig 1) This suggests anincreased likelihood of obtaining a response to K rather than N in
Switchgrass Response to Applied Nitrogen 1215
ORDER REPRINTS
Table
7
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
273649
35478
70045
b2962
b18430
b2215
a151
Cutting
239889
137708
102599
b392
18
1398
56
Ntiming
31062
151319
7734
76
4818
105
14
Nrate
3118782
a202660
47764
157
a1925
1045
184
CuttingaN
rate
850489
92751
21729
a164
2875
1466
165
NtimingaN
rate
622391
217859
21916
189
3453
1344
161
Residualerror
44
28679
173477
12329
94
2004
620
112
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
106
1889
972
162
442
261
147
112
1harvest
84
1239
1058
136
577
268
124
224
1harvest
102
1812
1033
173
448
276
145
448
1harvest
119
1970
1530
177
535
326
166
896
1harvest
104
2349
1840
222
522
323
178
02harvests
87
1110
1283
112
330
257
110
112
2harvests
103
1596
1662
139
534
350
147
1216 Thomason et al
ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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ORDER REPRINTS
Table
2
Initialsoilchem
icalcharacteristics
(0ndash15cm
)andclassificationatChickashaandPerkinsOK
Location
pH
a
NH
4-N
NO
3-N
Pb
Kb
TotalN
cOrganic
Cc
Dbinitial
Db2001
(mgkg1)
(mgg1)
(gcm
3)
Chickasha
69
758
112
28
215
006
82
143
141
ClassificationDale
siltloam
(fine-siltymixedsuperactive
thermic
Pachic
Haplustoll)
Perkins
67
753
21
77
325
09
68
147
147
ClassificationTellersandyloam
(fine-loamymixedactive
thermic
Udic
Argiustoll)
Dbbulk
density
(gcm
3)
apH11
soilwater
bPandKMehlich
III
cOrganic
CandtotalNdry
combustion
1204 Thomason et al
ORDER REPRINTS
summer one in late summer and one at the end of the season producedmore biomass (277Mgha1) compared to one harvest at the end of theseason (186Mgha1) These results reflect the ideal weather conditionspresent in 1997 that resulted in high yields Three harvests resulted inhigher N uptake values than those with fewer cuttings even when yieldswere higher for plots with fewer cutting dates (Table 3) The lowest Nuptake values for any treatment occurred with lower N rates (less than224 kg ha1) and one or two cuttings Three harvests increased K uptakeby the plants and split-applying the N over three dates resulted in more Kuptake than with two N application dates Neither treatment removed asmuch K as those with all N applied in April This is plausible consideringthe amount of K removed in the stems Phosphorus uptake levels wereon average approximately ten times lower than N or K uptake levelsThis was expected based on previous work documenting NP ratios of101[20] Splitting N applications over two dates resulted in lower Premoval than when applying all N early in the season (Table 3)
In 1998 a significant response to applied N was observed Howeverno differences in harvest frequency were noted probably due to the lackof rainfall in mid-summer Total yields were much lower than in 1997Lower rates of early season N and the removal of forage in late-summerdecreased yields in plots with three harvests and three-way split Napplications when compared to those cut twice Although yields werelower in 1998 maximum N uptake was higher than 1997 (375 and330 kg ha1 respectively) There was no difference in N uptake untiltotal N rates reached 224 kg ha1 Potassium uptake values were foundto follow the same trend as N Maximum K uptake occurred withthree-harvests and lowest values with one-harvest (Table 4)
Yields were again high at the Chickasha site in 1999 with some plotsproducing over 20Mgha1 (Table 5) The average yield for the site was17Mgha1 The highest levels of N uptake were observed with splitapplications of N and multiple harvests Uptake of K mirrored that forN in that number of harvests was highly significant and multipleharvests tended to remove more K than one harvest Phosphorus uptakewas greatest for three harvests regardless of N timing (353 and154 kg ha1 for three and one harvest respectively)
Yields for 2000 represent only the first two scheduled harvests for theyear and not the final end of season harvest Due to heavy fall rainsharvest was delayed and due to lack of communication the area wasburned before the final harvest could be taken Therefore yields shown inTable 6 represent the sum of only two cuttings The highest yields werecut two times (scheduled for three) and either not fertilized or fertilizedat the lowest rate of 112 kgNha1 (154 and 157Mgha1) Nitrogen
Switchgrass Response to Applied Nitrogen 1205
ORDER REPRINTS
Table
3
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1997
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
238501
10941
28072
258
441
1491
191
Cutting
24132329
b709443
b1344882
b6236
b9809
11234
b4789
b
Ntiming
3361873
10535
37908
134
30
19
58
Nrate
31564708
a209208
a171088
a15333
2605
2557
534
a
CuttingaN
rate
8707859
56216
26387
393
1526
2166
302
NtimingaN
rate
6651074
41644
60091
527
1232
2031
314
Residualerror
44
478953
38207
52088
473
1924
1917
288
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
222
1650
1689
195
386
400
131
112
1harvest
174
1177
1247
134
337
372
104
224
1harvest
164
1406
1285
154
284
310
100
448
1harvest
169
1186
1311
135
322
352
105
896
1harvest
203
1541
1489
173
394
390
127
02harvests
334
2548
2612
296
552
600
208
112
2harvests
155
1536
1521
161
403
344
118
1206 Thomason et al
ORDER REPRINTS
224
2harvests
337
2825
2694
284
643
688
222
448
2harvests
296
2830
2842
310
531
589
206
896
2harvests
244
2311
2337
217
403
464
163
03harvests
267
2325
3136
267
520
594
182
112
3harvests
249
2151
2902
244
348
389
193
224
3harvests
277
2608
3358
293
420
432
237
448
3harvests
309
3000
3814
333
425
473
265
896
3harvests
286
3202
3275
268
420
449
250
112
2-spN2harv
241
2037
1976
216
420
490
160
224
2-spN2harv
253
2091
1958
219
482
492
162
448
2-spN2harv
367
3306
3413
382
626
691
243
896
2-spN2harv
202
1950
1714
212
416
424
148
112
3-spN3harv
247
2101
2677
237
354
416
220
224
3-spN3harv
199
1821
2191
202
322
342
164
448
3-spN3harv
318
2145
3687
325
490
485
251
896
3-spN3harv
291
2739
3411
313
433
469
254
SED
57
505
589
53
113
113
44
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1207
ORDER REPRINTS
Table
4
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2996539
a87600
205053
a636
9278
15536
1010
Cutting
2372035
414096
a653177
b1024
1009
1563
266
Ntiming
3576196
111018
185774
a936
4895
6344
804
Nrate
3811575
a33003
62676
a527
a4584
a5872
336
a
CuttingaN
rate
8239068
59376
64205
400
6028
10433
560
NtimingaN
rate
6168684
34597
43532
180
2624
7172
282
Residualerror
44
220581
50460
52109
412
3338
4005
318
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
166
2048
1902
221
689
592
180
112
1harvest
141
1780
1875
195
601
638
164
224
1harvest
158
2127
2119
207
698
668
183
448
1harvest
172
2170
2212
211
726
747
200
896
1harvest
100
1328
1256
117
434
430
114
02harvests
166
2232
2468
225
677
776
205
112
2harvests
112
1548
1610
169
436
438
124
224
2harvests
226
3000
3378
311
910
1046
277
1208 Thomason et al
ORDER REPRINTS
448
2harvests
147
1956
1855
187
309
300
98
896
2harvests
162
2265
2241
191
575
680
190
03harvests
215
3403
3473
280
671
819
228
112
3harvests
168
2352
2705
201
533
658
184
224
3harvests
205
2833
3432
253
616
716
205
448
3harvests
245
3756
3864
289
641
668
190
896
3harvests
147
2229
2377
189
487
537
165
112
2-spN2harv
175
2119
2455
247
614
757
213
224
2-spN2harv
200
2677
3123
289
777
846
258
448
2-spN2harv
158
2070
2464
212
601
725
200
896
2-spN2harv
156
2355
2207
220
621
609
201
112
3-spN3harv
141
1962
2110
164
425
522
140
224
3-spN3harv
146
2233
2228
183
520
567
169
448
3-spN3harv
175
2375
2739
219
531
619
172
896
3-spN3harv
135
2210
2376
172
463
534
162
SED
12
580
589
52
149
163
46
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1209
ORDER REPRINTS
Table
5
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2464423
865906
1102070
a13008
a1665
6961
a291
Cutting
245101
952918
a1038877
b14290
b139
209
2203
b
Ntiming
3120137
133208
134666
1091
3230
2274
789
a
Nrate
32430687
717517
596007
4215
1799
2500
102
CuttingaN
rate
8207490
28101
43658
250
4465
b4667
a380
NtimingaN
rate
62060595
493140
380903
3444
810
1207
159
Residualerror
44
1562737
391299
334675
3504
1491
1808
291
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
109
781
1011
124
328
380
93
112
1harvest
150
1577
1541
171
478
532
145
224
1harvest
162
1459
1954
189
436
581
131
448
1harvest
191
1800
2386
181
693
715
180
896
1harvest
114
1257
1095
104
345
363
98
02harvests
179
2278
2736
274
543
602
192
112
2harvests
132
1754
2237
211
416
432
149
224
2harvests
170
2210
2453
244
530
614
182
1210 Thomason et al
ORDER REPRINTS
448
2harvests
162
2172
2291
221
352
400
120
896
2harvests
173
2474
2514
216
534
584
180
03harvests
200
2750
3273
352
500
559
205
112
3harvests
185
3150
3450
379
533
515
249
224
3harvests
167
2787
3303
335
392
436
184
448
3harvests
191
3300
3491
368
480
530
207
896
3harvests
154
2857
3000
331
431
472
194
112
2-spN2harv
145
1794
2258
226
432
469
156
224
2-spN2harv
146
1808
2078
223
564
501
195
448
2-spN2harv
175
2181
2713
248
487
557
171
896
2-spN2harv
208
2702
3557
288
654
703
220
112
3-spN3harv
155
2220
2522
260
353
381
145
224
3-spN3harv
152
2501
2949
304
412
401
174
448
3-spN3harv
180
2707
3137
354
405
475
170
896
3-spN3harv
263
3328
3144
425
366
401
167
SED
102
1573
1494
153
100
110
38
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1211
ORDER REPRINTS
Table
6
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2194823
b35769
a23391
1497
b1151
2969
b240
a
Cutting
2325370
b727339
b1445641
b9451
b2978
b1602
769
b
Ntiming
318979
a10279
15723
60
663
380
28
Nrate
3131730
b13237
24928
765
344
1865
a124
CuttingaN
rate
874236
a32484
a29096
491
1268
a1213
105
NtimingaN
rate
629574
7762
26341
384
237
239
41
Residualerror
44
31244
8263
16602
157
352
385
52
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
mdashmdash
mdashmdash
mdashmdash
mdash
112
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
224
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
448
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
896
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
02harvests
140
1493
1923
217
320
439
132
112
2harvests
110
1252
1516
203
264
345
106
224
2harvests
125
1334
1942
193
277
418
109
1212 Thomason et al
ORDER REPRINTS
448
2harvests
117
1485
1232
185
264
361
114
896
2harvests
102
1509
1217
152
315
338
104
03harvests
154
2564
3177
317
389
481
171
112
3harvests
157
2560
3317
347
387
507
170
224
3harvests
141
2477
3183
336
376
434
177
448
3harvests
154
2719
3084
342
384
451
180
896
3harvests
92
1676
2012
170
218
258
110
112
2-spN2harv
103
1123
1262
167
225
319
97
224
2-spN2harv
125
1265
1468
192
282
404
108
448
2-spN2harv
107
1212
1350
185
232
353
98
896
2-spN2harv
106
1419
1490
164
260
325
101
112
3-spN3harv
139
2238
2762
280
346
418
154
224
3-spN3harv
120
2194
2474
268
281
361
145
448
3-spN3harv
144
2504
3053
336
338
441
178
896
3-spN3harv
112
2013
2427
259
253
297
134
SED
14
235
333
32
49
51
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1213
ORDER REPRINTS
uptake of 240 kgNha1 was highest for two harvests (scheduled for
three) and April fertilization (Table 6) Potassium uptake was highest
with multiple harvests The lack of the final harvest for this data set
severely limited interpretation
Perkins
Yields in 1998 were lower than those at Chickasha due to sandier
soil and less total rainfall Treatment combinations with two or three
harvests and split N applications produced the highest yields averaging
over 11Mgha1 Forage nitrogen concentration did not increase
with increasing yields as was the trend over all years (Fig 1) Potassium
uptake was maximized with two harvests and either one or two N
applications both averaging near 180 kgKha1 Uptake of P was
significantly affected by N rate and was greatest with one harvest and
one N application date at 174 kg ha1 (Table 7) Phosphorus uptake
decreased with multiple harvestsPerkins again produced much lower yields than Chickasha in 1999
and significant differences were noted due to number of harvests and N
timing (Table 8) Average yields were highest for the three harvests three-
way split N treatments (Table 8) Multiple harvests increased crop N
uptake over those with the same total N rates and one harvest Potassium
uptake was high for all multiple harvest plots In fact one harvest
0
05
1
15
2
25
3
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
KN
y = 00002x - 16581 R2= 07749
y = 5E-05x + 04825 R2= 02171
Figure 1 N and K concentrations with increasing dry biomass yields Chickasha
and Perkins (View this art in color at wwwdekkercom)
1214 Thomason et al
ORDER REPRINTS
removed little more than half of the K of two or three harvests (775 vs1552 kg ha1) Three harvests also resulted in increased P uptake
Dry matter yield in 2000 averaged over N rate was 133Mgha1
(Table 9) Nitrogen removal was maximized with three harvests andsplitting N into three applications (Table 9) There was a trend towardincreased N uptake with increasing harvest frequency and increasing Nrate Three harvests with N split into three increments resulted in 48more K uptake than two harvests and two N application dates (896 vs1844 kg ha1) The highest average P uptake was found for three harvestsand three-way split N applications (202 kg ha1) (Table 9)
Soil Carbon
Organic C data from in crown and between crown samples werecompared to organic C from initial samples from the area to determine ifchanges had occurred Bulk density measurements taken from theexperimental area did not differ from an adjacent area that wasconventionally tilled Initial samples indicated average soil organic C(SOC) for the site of 68 and 82mg g1 for Perkins and Chickasharespectively These results are possibly confounded by known spatialvariability in SOC reported by Raun et al[21] Contrast comparisons founda significant linear decrease in SOC with increasing N rates and twoharvests for the Chickasha crown sampling (Table 10) A significantquadratic increase was noted for Perkins in crown samples and asignificant quadratic decrease in SOC with increasing N rate was foundfor between crown samples at Chickasha Taken together there seem to beno obvious trends toward increasing or decreasing SOC at either site Thisis potentially influenced by the fact that aboveground biomass wasremoved from the site Garten and Wullschleger[22] have estimated that itmay take a decade of switchgrass production to sequester a significantmeasurable amount of soil carbon Given more time SOC may increasebut the short duration (3ndash5 yrs) of this study has provided no real evidencesupporting this increase in SOC especially in the lsquolsquobetween crownrsquorsquosamples
CONCLUSIONS
Overall forage K concentrations increased with increasing yieldwhile N concentrations were not affected (Fig 1) This suggests anincreased likelihood of obtaining a response to K rather than N in
Switchgrass Response to Applied Nitrogen 1215
ORDER REPRINTS
Table
7
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
273649
35478
70045
b2962
b18430
b2215
a151
Cutting
239889
137708
102599
b392
18
1398
56
Ntiming
31062
151319
7734
76
4818
105
14
Nrate
3118782
a202660
47764
157
a1925
1045
184
CuttingaN
rate
850489
92751
21729
a164
2875
1466
165
NtimingaN
rate
622391
217859
21916
189
3453
1344
161
Residualerror
44
28679
173477
12329
94
2004
620
112
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
106
1889
972
162
442
261
147
112
1harvest
84
1239
1058
136
577
268
124
224
1harvest
102
1812
1033
173
448
276
145
448
1harvest
119
1970
1530
177
535
326
166
896
1harvest
104
2349
1840
222
522
323
178
02harvests
87
1110
1283
112
330
257
110
112
2harvests
103
1596
1662
139
534
350
147
1216 Thomason et al
ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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ORDER REPRINTS
summer one in late summer and one at the end of the season producedmore biomass (277Mgha1) compared to one harvest at the end of theseason (186Mgha1) These results reflect the ideal weather conditionspresent in 1997 that resulted in high yields Three harvests resulted inhigher N uptake values than those with fewer cuttings even when yieldswere higher for plots with fewer cutting dates (Table 3) The lowest Nuptake values for any treatment occurred with lower N rates (less than224 kg ha1) and one or two cuttings Three harvests increased K uptakeby the plants and split-applying the N over three dates resulted in more Kuptake than with two N application dates Neither treatment removed asmuch K as those with all N applied in April This is plausible consideringthe amount of K removed in the stems Phosphorus uptake levels wereon average approximately ten times lower than N or K uptake levelsThis was expected based on previous work documenting NP ratios of101[20] Splitting N applications over two dates resulted in lower Premoval than when applying all N early in the season (Table 3)
In 1998 a significant response to applied N was observed Howeverno differences in harvest frequency were noted probably due to the lackof rainfall in mid-summer Total yields were much lower than in 1997Lower rates of early season N and the removal of forage in late-summerdecreased yields in plots with three harvests and three-way split Napplications when compared to those cut twice Although yields werelower in 1998 maximum N uptake was higher than 1997 (375 and330 kg ha1 respectively) There was no difference in N uptake untiltotal N rates reached 224 kg ha1 Potassium uptake values were foundto follow the same trend as N Maximum K uptake occurred withthree-harvests and lowest values with one-harvest (Table 4)
Yields were again high at the Chickasha site in 1999 with some plotsproducing over 20Mgha1 (Table 5) The average yield for the site was17Mgha1 The highest levels of N uptake were observed with splitapplications of N and multiple harvests Uptake of K mirrored that forN in that number of harvests was highly significant and multipleharvests tended to remove more K than one harvest Phosphorus uptakewas greatest for three harvests regardless of N timing (353 and154 kg ha1 for three and one harvest respectively)
Yields for 2000 represent only the first two scheduled harvests for theyear and not the final end of season harvest Due to heavy fall rainsharvest was delayed and due to lack of communication the area wasburned before the final harvest could be taken Therefore yields shown inTable 6 represent the sum of only two cuttings The highest yields werecut two times (scheduled for three) and either not fertilized or fertilizedat the lowest rate of 112 kgNha1 (154 and 157Mgha1) Nitrogen
Switchgrass Response to Applied Nitrogen 1205
ORDER REPRINTS
Table
3
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1997
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
238501
10941
28072
258
441
1491
191
Cutting
24132329
b709443
b1344882
b6236
b9809
11234
b4789
b
Ntiming
3361873
10535
37908
134
30
19
58
Nrate
31564708
a209208
a171088
a15333
2605
2557
534
a
CuttingaN
rate
8707859
56216
26387
393
1526
2166
302
NtimingaN
rate
6651074
41644
60091
527
1232
2031
314
Residualerror
44
478953
38207
52088
473
1924
1917
288
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
222
1650
1689
195
386
400
131
112
1harvest
174
1177
1247
134
337
372
104
224
1harvest
164
1406
1285
154
284
310
100
448
1harvest
169
1186
1311
135
322
352
105
896
1harvest
203
1541
1489
173
394
390
127
02harvests
334
2548
2612
296
552
600
208
112
2harvests
155
1536
1521
161
403
344
118
1206 Thomason et al
ORDER REPRINTS
224
2harvests
337
2825
2694
284
643
688
222
448
2harvests
296
2830
2842
310
531
589
206
896
2harvests
244
2311
2337
217
403
464
163
03harvests
267
2325
3136
267
520
594
182
112
3harvests
249
2151
2902
244
348
389
193
224
3harvests
277
2608
3358
293
420
432
237
448
3harvests
309
3000
3814
333
425
473
265
896
3harvests
286
3202
3275
268
420
449
250
112
2-spN2harv
241
2037
1976
216
420
490
160
224
2-spN2harv
253
2091
1958
219
482
492
162
448
2-spN2harv
367
3306
3413
382
626
691
243
896
2-spN2harv
202
1950
1714
212
416
424
148
112
3-spN3harv
247
2101
2677
237
354
416
220
224
3-spN3harv
199
1821
2191
202
322
342
164
448
3-spN3harv
318
2145
3687
325
490
485
251
896
3-spN3harv
291
2739
3411
313
433
469
254
SED
57
505
589
53
113
113
44
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1207
ORDER REPRINTS
Table
4
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2996539
a87600
205053
a636
9278
15536
1010
Cutting
2372035
414096
a653177
b1024
1009
1563
266
Ntiming
3576196
111018
185774
a936
4895
6344
804
Nrate
3811575
a33003
62676
a527
a4584
a5872
336
a
CuttingaN
rate
8239068
59376
64205
400
6028
10433
560
NtimingaN
rate
6168684
34597
43532
180
2624
7172
282
Residualerror
44
220581
50460
52109
412
3338
4005
318
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
166
2048
1902
221
689
592
180
112
1harvest
141
1780
1875
195
601
638
164
224
1harvest
158
2127
2119
207
698
668
183
448
1harvest
172
2170
2212
211
726
747
200
896
1harvest
100
1328
1256
117
434
430
114
02harvests
166
2232
2468
225
677
776
205
112
2harvests
112
1548
1610
169
436
438
124
224
2harvests
226
3000
3378
311
910
1046
277
1208 Thomason et al
ORDER REPRINTS
448
2harvests
147
1956
1855
187
309
300
98
896
2harvests
162
2265
2241
191
575
680
190
03harvests
215
3403
3473
280
671
819
228
112
3harvests
168
2352
2705
201
533
658
184
224
3harvests
205
2833
3432
253
616
716
205
448
3harvests
245
3756
3864
289
641
668
190
896
3harvests
147
2229
2377
189
487
537
165
112
2-spN2harv
175
2119
2455
247
614
757
213
224
2-spN2harv
200
2677
3123
289
777
846
258
448
2-spN2harv
158
2070
2464
212
601
725
200
896
2-spN2harv
156
2355
2207
220
621
609
201
112
3-spN3harv
141
1962
2110
164
425
522
140
224
3-spN3harv
146
2233
2228
183
520
567
169
448
3-spN3harv
175
2375
2739
219
531
619
172
896
3-spN3harv
135
2210
2376
172
463
534
162
SED
12
580
589
52
149
163
46
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1209
ORDER REPRINTS
Table
5
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2464423
865906
1102070
a13008
a1665
6961
a291
Cutting
245101
952918
a1038877
b14290
b139
209
2203
b
Ntiming
3120137
133208
134666
1091
3230
2274
789
a
Nrate
32430687
717517
596007
4215
1799
2500
102
CuttingaN
rate
8207490
28101
43658
250
4465
b4667
a380
NtimingaN
rate
62060595
493140
380903
3444
810
1207
159
Residualerror
44
1562737
391299
334675
3504
1491
1808
291
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
109
781
1011
124
328
380
93
112
1harvest
150
1577
1541
171
478
532
145
224
1harvest
162
1459
1954
189
436
581
131
448
1harvest
191
1800
2386
181
693
715
180
896
1harvest
114
1257
1095
104
345
363
98
02harvests
179
2278
2736
274
543
602
192
112
2harvests
132
1754
2237
211
416
432
149
224
2harvests
170
2210
2453
244
530
614
182
1210 Thomason et al
ORDER REPRINTS
448
2harvests
162
2172
2291
221
352
400
120
896
2harvests
173
2474
2514
216
534
584
180
03harvests
200
2750
3273
352
500
559
205
112
3harvests
185
3150
3450
379
533
515
249
224
3harvests
167
2787
3303
335
392
436
184
448
3harvests
191
3300
3491
368
480
530
207
896
3harvests
154
2857
3000
331
431
472
194
112
2-spN2harv
145
1794
2258
226
432
469
156
224
2-spN2harv
146
1808
2078
223
564
501
195
448
2-spN2harv
175
2181
2713
248
487
557
171
896
2-spN2harv
208
2702
3557
288
654
703
220
112
3-spN3harv
155
2220
2522
260
353
381
145
224
3-spN3harv
152
2501
2949
304
412
401
174
448
3-spN3harv
180
2707
3137
354
405
475
170
896
3-spN3harv
263
3328
3144
425
366
401
167
SED
102
1573
1494
153
100
110
38
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1211
ORDER REPRINTS
Table
6
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2194823
b35769
a23391
1497
b1151
2969
b240
a
Cutting
2325370
b727339
b1445641
b9451
b2978
b1602
769
b
Ntiming
318979
a10279
15723
60
663
380
28
Nrate
3131730
b13237
24928
765
344
1865
a124
CuttingaN
rate
874236
a32484
a29096
491
1268
a1213
105
NtimingaN
rate
629574
7762
26341
384
237
239
41
Residualerror
44
31244
8263
16602
157
352
385
52
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
mdashmdash
mdashmdash
mdashmdash
mdash
112
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
224
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
448
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
896
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
02harvests
140
1493
1923
217
320
439
132
112
2harvests
110
1252
1516
203
264
345
106
224
2harvests
125
1334
1942
193
277
418
109
1212 Thomason et al
ORDER REPRINTS
448
2harvests
117
1485
1232
185
264
361
114
896
2harvests
102
1509
1217
152
315
338
104
03harvests
154
2564
3177
317
389
481
171
112
3harvests
157
2560
3317
347
387
507
170
224
3harvests
141
2477
3183
336
376
434
177
448
3harvests
154
2719
3084
342
384
451
180
896
3harvests
92
1676
2012
170
218
258
110
112
2-spN2harv
103
1123
1262
167
225
319
97
224
2-spN2harv
125
1265
1468
192
282
404
108
448
2-spN2harv
107
1212
1350
185
232
353
98
896
2-spN2harv
106
1419
1490
164
260
325
101
112
3-spN3harv
139
2238
2762
280
346
418
154
224
3-spN3harv
120
2194
2474
268
281
361
145
448
3-spN3harv
144
2504
3053
336
338
441
178
896
3-spN3harv
112
2013
2427
259
253
297
134
SED
14
235
333
32
49
51
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1213
ORDER REPRINTS
uptake of 240 kgNha1 was highest for two harvests (scheduled for
three) and April fertilization (Table 6) Potassium uptake was highest
with multiple harvests The lack of the final harvest for this data set
severely limited interpretation
Perkins
Yields in 1998 were lower than those at Chickasha due to sandier
soil and less total rainfall Treatment combinations with two or three
harvests and split N applications produced the highest yields averaging
over 11Mgha1 Forage nitrogen concentration did not increase
with increasing yields as was the trend over all years (Fig 1) Potassium
uptake was maximized with two harvests and either one or two N
applications both averaging near 180 kgKha1 Uptake of P was
significantly affected by N rate and was greatest with one harvest and
one N application date at 174 kg ha1 (Table 7) Phosphorus uptake
decreased with multiple harvestsPerkins again produced much lower yields than Chickasha in 1999
and significant differences were noted due to number of harvests and N
timing (Table 8) Average yields were highest for the three harvests three-
way split N treatments (Table 8) Multiple harvests increased crop N
uptake over those with the same total N rates and one harvest Potassium
uptake was high for all multiple harvest plots In fact one harvest
0
05
1
15
2
25
3
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
KN
y = 00002x - 16581 R2= 07749
y = 5E-05x + 04825 R2= 02171
Figure 1 N and K concentrations with increasing dry biomass yields Chickasha
and Perkins (View this art in color at wwwdekkercom)
1214 Thomason et al
ORDER REPRINTS
removed little more than half of the K of two or three harvests (775 vs1552 kg ha1) Three harvests also resulted in increased P uptake
Dry matter yield in 2000 averaged over N rate was 133Mgha1
(Table 9) Nitrogen removal was maximized with three harvests andsplitting N into three applications (Table 9) There was a trend towardincreased N uptake with increasing harvest frequency and increasing Nrate Three harvests with N split into three increments resulted in 48more K uptake than two harvests and two N application dates (896 vs1844 kg ha1) The highest average P uptake was found for three harvestsand three-way split N applications (202 kg ha1) (Table 9)
Soil Carbon
Organic C data from in crown and between crown samples werecompared to organic C from initial samples from the area to determine ifchanges had occurred Bulk density measurements taken from theexperimental area did not differ from an adjacent area that wasconventionally tilled Initial samples indicated average soil organic C(SOC) for the site of 68 and 82mg g1 for Perkins and Chickasharespectively These results are possibly confounded by known spatialvariability in SOC reported by Raun et al[21] Contrast comparisons founda significant linear decrease in SOC with increasing N rates and twoharvests for the Chickasha crown sampling (Table 10) A significantquadratic increase was noted for Perkins in crown samples and asignificant quadratic decrease in SOC with increasing N rate was foundfor between crown samples at Chickasha Taken together there seem to beno obvious trends toward increasing or decreasing SOC at either site Thisis potentially influenced by the fact that aboveground biomass wasremoved from the site Garten and Wullschleger[22] have estimated that itmay take a decade of switchgrass production to sequester a significantmeasurable amount of soil carbon Given more time SOC may increasebut the short duration (3ndash5 yrs) of this study has provided no real evidencesupporting this increase in SOC especially in the lsquolsquobetween crownrsquorsquosamples
CONCLUSIONS
Overall forage K concentrations increased with increasing yieldwhile N concentrations were not affected (Fig 1) This suggests anincreased likelihood of obtaining a response to K rather than N in
Switchgrass Response to Applied Nitrogen 1215
ORDER REPRINTS
Table
7
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
273649
35478
70045
b2962
b18430
b2215
a151
Cutting
239889
137708
102599
b392
18
1398
56
Ntiming
31062
151319
7734
76
4818
105
14
Nrate
3118782
a202660
47764
157
a1925
1045
184
CuttingaN
rate
850489
92751
21729
a164
2875
1466
165
NtimingaN
rate
622391
217859
21916
189
3453
1344
161
Residualerror
44
28679
173477
12329
94
2004
620
112
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
106
1889
972
162
442
261
147
112
1harvest
84
1239
1058
136
577
268
124
224
1harvest
102
1812
1033
173
448
276
145
448
1harvest
119
1970
1530
177
535
326
166
896
1harvest
104
2349
1840
222
522
323
178
02harvests
87
1110
1283
112
330
257
110
112
2harvests
103
1596
1662
139
534
350
147
1216 Thomason et al
ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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ORDER REPRINTS
Table
3
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1997
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
238501
10941
28072
258
441
1491
191
Cutting
24132329
b709443
b1344882
b6236
b9809
11234
b4789
b
Ntiming
3361873
10535
37908
134
30
19
58
Nrate
31564708
a209208
a171088
a15333
2605
2557
534
a
CuttingaN
rate
8707859
56216
26387
393
1526
2166
302
NtimingaN
rate
6651074
41644
60091
527
1232
2031
314
Residualerror
44
478953
38207
52088
473
1924
1917
288
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
222
1650
1689
195
386
400
131
112
1harvest
174
1177
1247
134
337
372
104
224
1harvest
164
1406
1285
154
284
310
100
448
1harvest
169
1186
1311
135
322
352
105
896
1harvest
203
1541
1489
173
394
390
127
02harvests
334
2548
2612
296
552
600
208
112
2harvests
155
1536
1521
161
403
344
118
1206 Thomason et al
ORDER REPRINTS
224
2harvests
337
2825
2694
284
643
688
222
448
2harvests
296
2830
2842
310
531
589
206
896
2harvests
244
2311
2337
217
403
464
163
03harvests
267
2325
3136
267
520
594
182
112
3harvests
249
2151
2902
244
348
389
193
224
3harvests
277
2608
3358
293
420
432
237
448
3harvests
309
3000
3814
333
425
473
265
896
3harvests
286
3202
3275
268
420
449
250
112
2-spN2harv
241
2037
1976
216
420
490
160
224
2-spN2harv
253
2091
1958
219
482
492
162
448
2-spN2harv
367
3306
3413
382
626
691
243
896
2-spN2harv
202
1950
1714
212
416
424
148
112
3-spN3harv
247
2101
2677
237
354
416
220
224
3-spN3harv
199
1821
2191
202
322
342
164
448
3-spN3harv
318
2145
3687
325
490
485
251
896
3-spN3harv
291
2739
3411
313
433
469
254
SED
57
505
589
53
113
113
44
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1207
ORDER REPRINTS
Table
4
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2996539
a87600
205053
a636
9278
15536
1010
Cutting
2372035
414096
a653177
b1024
1009
1563
266
Ntiming
3576196
111018
185774
a936
4895
6344
804
Nrate
3811575
a33003
62676
a527
a4584
a5872
336
a
CuttingaN
rate
8239068
59376
64205
400
6028
10433
560
NtimingaN
rate
6168684
34597
43532
180
2624
7172
282
Residualerror
44
220581
50460
52109
412
3338
4005
318
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
166
2048
1902
221
689
592
180
112
1harvest
141
1780
1875
195
601
638
164
224
1harvest
158
2127
2119
207
698
668
183
448
1harvest
172
2170
2212
211
726
747
200
896
1harvest
100
1328
1256
117
434
430
114
02harvests
166
2232
2468
225
677
776
205
112
2harvests
112
1548
1610
169
436
438
124
224
2harvests
226
3000
3378
311
910
1046
277
1208 Thomason et al
ORDER REPRINTS
448
2harvests
147
1956
1855
187
309
300
98
896
2harvests
162
2265
2241
191
575
680
190
03harvests
215
3403
3473
280
671
819
228
112
3harvests
168
2352
2705
201
533
658
184
224
3harvests
205
2833
3432
253
616
716
205
448
3harvests
245
3756
3864
289
641
668
190
896
3harvests
147
2229
2377
189
487
537
165
112
2-spN2harv
175
2119
2455
247
614
757
213
224
2-spN2harv
200
2677
3123
289
777
846
258
448
2-spN2harv
158
2070
2464
212
601
725
200
896
2-spN2harv
156
2355
2207
220
621
609
201
112
3-spN3harv
141
1962
2110
164
425
522
140
224
3-spN3harv
146
2233
2228
183
520
567
169
448
3-spN3harv
175
2375
2739
219
531
619
172
896
3-spN3harv
135
2210
2376
172
463
534
162
SED
12
580
589
52
149
163
46
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1209
ORDER REPRINTS
Table
5
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2464423
865906
1102070
a13008
a1665
6961
a291
Cutting
245101
952918
a1038877
b14290
b139
209
2203
b
Ntiming
3120137
133208
134666
1091
3230
2274
789
a
Nrate
32430687
717517
596007
4215
1799
2500
102
CuttingaN
rate
8207490
28101
43658
250
4465
b4667
a380
NtimingaN
rate
62060595
493140
380903
3444
810
1207
159
Residualerror
44
1562737
391299
334675
3504
1491
1808
291
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
109
781
1011
124
328
380
93
112
1harvest
150
1577
1541
171
478
532
145
224
1harvest
162
1459
1954
189
436
581
131
448
1harvest
191
1800
2386
181
693
715
180
896
1harvest
114
1257
1095
104
345
363
98
02harvests
179
2278
2736
274
543
602
192
112
2harvests
132
1754
2237
211
416
432
149
224
2harvests
170
2210
2453
244
530
614
182
1210 Thomason et al
ORDER REPRINTS
448
2harvests
162
2172
2291
221
352
400
120
896
2harvests
173
2474
2514
216
534
584
180
03harvests
200
2750
3273
352
500
559
205
112
3harvests
185
3150
3450
379
533
515
249
224
3harvests
167
2787
3303
335
392
436
184
448
3harvests
191
3300
3491
368
480
530
207
896
3harvests
154
2857
3000
331
431
472
194
112
2-spN2harv
145
1794
2258
226
432
469
156
224
2-spN2harv
146
1808
2078
223
564
501
195
448
2-spN2harv
175
2181
2713
248
487
557
171
896
2-spN2harv
208
2702
3557
288
654
703
220
112
3-spN3harv
155
2220
2522
260
353
381
145
224
3-spN3harv
152
2501
2949
304
412
401
174
448
3-spN3harv
180
2707
3137
354
405
475
170
896
3-spN3harv
263
3328
3144
425
366
401
167
SED
102
1573
1494
153
100
110
38
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1211
ORDER REPRINTS
Table
6
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2194823
b35769
a23391
1497
b1151
2969
b240
a
Cutting
2325370
b727339
b1445641
b9451
b2978
b1602
769
b
Ntiming
318979
a10279
15723
60
663
380
28
Nrate
3131730
b13237
24928
765
344
1865
a124
CuttingaN
rate
874236
a32484
a29096
491
1268
a1213
105
NtimingaN
rate
629574
7762
26341
384
237
239
41
Residualerror
44
31244
8263
16602
157
352
385
52
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
mdashmdash
mdashmdash
mdashmdash
mdash
112
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
224
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
448
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
896
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
02harvests
140
1493
1923
217
320
439
132
112
2harvests
110
1252
1516
203
264
345
106
224
2harvests
125
1334
1942
193
277
418
109
1212 Thomason et al
ORDER REPRINTS
448
2harvests
117
1485
1232
185
264
361
114
896
2harvests
102
1509
1217
152
315
338
104
03harvests
154
2564
3177
317
389
481
171
112
3harvests
157
2560
3317
347
387
507
170
224
3harvests
141
2477
3183
336
376
434
177
448
3harvests
154
2719
3084
342
384
451
180
896
3harvests
92
1676
2012
170
218
258
110
112
2-spN2harv
103
1123
1262
167
225
319
97
224
2-spN2harv
125
1265
1468
192
282
404
108
448
2-spN2harv
107
1212
1350
185
232
353
98
896
2-spN2harv
106
1419
1490
164
260
325
101
112
3-spN3harv
139
2238
2762
280
346
418
154
224
3-spN3harv
120
2194
2474
268
281
361
145
448
3-spN3harv
144
2504
3053
336
338
441
178
896
3-spN3harv
112
2013
2427
259
253
297
134
SED
14
235
333
32
49
51
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1213
ORDER REPRINTS
uptake of 240 kgNha1 was highest for two harvests (scheduled for
three) and April fertilization (Table 6) Potassium uptake was highest
with multiple harvests The lack of the final harvest for this data set
severely limited interpretation
Perkins
Yields in 1998 were lower than those at Chickasha due to sandier
soil and less total rainfall Treatment combinations with two or three
harvests and split N applications produced the highest yields averaging
over 11Mgha1 Forage nitrogen concentration did not increase
with increasing yields as was the trend over all years (Fig 1) Potassium
uptake was maximized with two harvests and either one or two N
applications both averaging near 180 kgKha1 Uptake of P was
significantly affected by N rate and was greatest with one harvest and
one N application date at 174 kg ha1 (Table 7) Phosphorus uptake
decreased with multiple harvestsPerkins again produced much lower yields than Chickasha in 1999
and significant differences were noted due to number of harvests and N
timing (Table 8) Average yields were highest for the three harvests three-
way split N treatments (Table 8) Multiple harvests increased crop N
uptake over those with the same total N rates and one harvest Potassium
uptake was high for all multiple harvest plots In fact one harvest
0
05
1
15
2
25
3
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
KN
y = 00002x - 16581 R2= 07749
y = 5E-05x + 04825 R2= 02171
Figure 1 N and K concentrations with increasing dry biomass yields Chickasha
and Perkins (View this art in color at wwwdekkercom)
1214 Thomason et al
ORDER REPRINTS
removed little more than half of the K of two or three harvests (775 vs1552 kg ha1) Three harvests also resulted in increased P uptake
Dry matter yield in 2000 averaged over N rate was 133Mgha1
(Table 9) Nitrogen removal was maximized with three harvests andsplitting N into three applications (Table 9) There was a trend towardincreased N uptake with increasing harvest frequency and increasing Nrate Three harvests with N split into three increments resulted in 48more K uptake than two harvests and two N application dates (896 vs1844 kg ha1) The highest average P uptake was found for three harvestsand three-way split N applications (202 kg ha1) (Table 9)
Soil Carbon
Organic C data from in crown and between crown samples werecompared to organic C from initial samples from the area to determine ifchanges had occurred Bulk density measurements taken from theexperimental area did not differ from an adjacent area that wasconventionally tilled Initial samples indicated average soil organic C(SOC) for the site of 68 and 82mg g1 for Perkins and Chickasharespectively These results are possibly confounded by known spatialvariability in SOC reported by Raun et al[21] Contrast comparisons founda significant linear decrease in SOC with increasing N rates and twoharvests for the Chickasha crown sampling (Table 10) A significantquadratic increase was noted for Perkins in crown samples and asignificant quadratic decrease in SOC with increasing N rate was foundfor between crown samples at Chickasha Taken together there seem to beno obvious trends toward increasing or decreasing SOC at either site Thisis potentially influenced by the fact that aboveground biomass wasremoved from the site Garten and Wullschleger[22] have estimated that itmay take a decade of switchgrass production to sequester a significantmeasurable amount of soil carbon Given more time SOC may increasebut the short duration (3ndash5 yrs) of this study has provided no real evidencesupporting this increase in SOC especially in the lsquolsquobetween crownrsquorsquosamples
CONCLUSIONS
Overall forage K concentrations increased with increasing yieldwhile N concentrations were not affected (Fig 1) This suggests anincreased likelihood of obtaining a response to K rather than N in
Switchgrass Response to Applied Nitrogen 1215
ORDER REPRINTS
Table
7
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
273649
35478
70045
b2962
b18430
b2215
a151
Cutting
239889
137708
102599
b392
18
1398
56
Ntiming
31062
151319
7734
76
4818
105
14
Nrate
3118782
a202660
47764
157
a1925
1045
184
CuttingaN
rate
850489
92751
21729
a164
2875
1466
165
NtimingaN
rate
622391
217859
21916
189
3453
1344
161
Residualerror
44
28679
173477
12329
94
2004
620
112
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
106
1889
972
162
442
261
147
112
1harvest
84
1239
1058
136
577
268
124
224
1harvest
102
1812
1033
173
448
276
145
448
1harvest
119
1970
1530
177
535
326
166
896
1harvest
104
2349
1840
222
522
323
178
02harvests
87
1110
1283
112
330
257
110
112
2harvests
103
1596
1662
139
534
350
147
1216 Thomason et al
ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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ORDER REPRINTS
224
2harvests
337
2825
2694
284
643
688
222
448
2harvests
296
2830
2842
310
531
589
206
896
2harvests
244
2311
2337
217
403
464
163
03harvests
267
2325
3136
267
520
594
182
112
3harvests
249
2151
2902
244
348
389
193
224
3harvests
277
2608
3358
293
420
432
237
448
3harvests
309
3000
3814
333
425
473
265
896
3harvests
286
3202
3275
268
420
449
250
112
2-spN2harv
241
2037
1976
216
420
490
160
224
2-spN2harv
253
2091
1958
219
482
492
162
448
2-spN2harv
367
3306
3413
382
626
691
243
896
2-spN2harv
202
1950
1714
212
416
424
148
112
3-spN3harv
247
2101
2677
237
354
416
220
224
3-spN3harv
199
1821
2191
202
322
342
164
448
3-spN3harv
318
2145
3687
325
490
485
251
896
3-spN3harv
291
2739
3411
313
433
469
254
SED
57
505
589
53
113
113
44
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1207
ORDER REPRINTS
Table
4
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2996539
a87600
205053
a636
9278
15536
1010
Cutting
2372035
414096
a653177
b1024
1009
1563
266
Ntiming
3576196
111018
185774
a936
4895
6344
804
Nrate
3811575
a33003
62676
a527
a4584
a5872
336
a
CuttingaN
rate
8239068
59376
64205
400
6028
10433
560
NtimingaN
rate
6168684
34597
43532
180
2624
7172
282
Residualerror
44
220581
50460
52109
412
3338
4005
318
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
166
2048
1902
221
689
592
180
112
1harvest
141
1780
1875
195
601
638
164
224
1harvest
158
2127
2119
207
698
668
183
448
1harvest
172
2170
2212
211
726
747
200
896
1harvest
100
1328
1256
117
434
430
114
02harvests
166
2232
2468
225
677
776
205
112
2harvests
112
1548
1610
169
436
438
124
224
2harvests
226
3000
3378
311
910
1046
277
1208 Thomason et al
ORDER REPRINTS
448
2harvests
147
1956
1855
187
309
300
98
896
2harvests
162
2265
2241
191
575
680
190
03harvests
215
3403
3473
280
671
819
228
112
3harvests
168
2352
2705
201
533
658
184
224
3harvests
205
2833
3432
253
616
716
205
448
3harvests
245
3756
3864
289
641
668
190
896
3harvests
147
2229
2377
189
487
537
165
112
2-spN2harv
175
2119
2455
247
614
757
213
224
2-spN2harv
200
2677
3123
289
777
846
258
448
2-spN2harv
158
2070
2464
212
601
725
200
896
2-spN2harv
156
2355
2207
220
621
609
201
112
3-spN3harv
141
1962
2110
164
425
522
140
224
3-spN3harv
146
2233
2228
183
520
567
169
448
3-spN3harv
175
2375
2739
219
531
619
172
896
3-spN3harv
135
2210
2376
172
463
534
162
SED
12
580
589
52
149
163
46
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1209
ORDER REPRINTS
Table
5
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2464423
865906
1102070
a13008
a1665
6961
a291
Cutting
245101
952918
a1038877
b14290
b139
209
2203
b
Ntiming
3120137
133208
134666
1091
3230
2274
789
a
Nrate
32430687
717517
596007
4215
1799
2500
102
CuttingaN
rate
8207490
28101
43658
250
4465
b4667
a380
NtimingaN
rate
62060595
493140
380903
3444
810
1207
159
Residualerror
44
1562737
391299
334675
3504
1491
1808
291
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
109
781
1011
124
328
380
93
112
1harvest
150
1577
1541
171
478
532
145
224
1harvest
162
1459
1954
189
436
581
131
448
1harvest
191
1800
2386
181
693
715
180
896
1harvest
114
1257
1095
104
345
363
98
02harvests
179
2278
2736
274
543
602
192
112
2harvests
132
1754
2237
211
416
432
149
224
2harvests
170
2210
2453
244
530
614
182
1210 Thomason et al
ORDER REPRINTS
448
2harvests
162
2172
2291
221
352
400
120
896
2harvests
173
2474
2514
216
534
584
180
03harvests
200
2750
3273
352
500
559
205
112
3harvests
185
3150
3450
379
533
515
249
224
3harvests
167
2787
3303
335
392
436
184
448
3harvests
191
3300
3491
368
480
530
207
896
3harvests
154
2857
3000
331
431
472
194
112
2-spN2harv
145
1794
2258
226
432
469
156
224
2-spN2harv
146
1808
2078
223
564
501
195
448
2-spN2harv
175
2181
2713
248
487
557
171
896
2-spN2harv
208
2702
3557
288
654
703
220
112
3-spN3harv
155
2220
2522
260
353
381
145
224
3-spN3harv
152
2501
2949
304
412
401
174
448
3-spN3harv
180
2707
3137
354
405
475
170
896
3-spN3harv
263
3328
3144
425
366
401
167
SED
102
1573
1494
153
100
110
38
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1211
ORDER REPRINTS
Table
6
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2194823
b35769
a23391
1497
b1151
2969
b240
a
Cutting
2325370
b727339
b1445641
b9451
b2978
b1602
769
b
Ntiming
318979
a10279
15723
60
663
380
28
Nrate
3131730
b13237
24928
765
344
1865
a124
CuttingaN
rate
874236
a32484
a29096
491
1268
a1213
105
NtimingaN
rate
629574
7762
26341
384
237
239
41
Residualerror
44
31244
8263
16602
157
352
385
52
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
mdashmdash
mdashmdash
mdashmdash
mdash
112
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
224
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
448
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
896
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
02harvests
140
1493
1923
217
320
439
132
112
2harvests
110
1252
1516
203
264
345
106
224
2harvests
125
1334
1942
193
277
418
109
1212 Thomason et al
ORDER REPRINTS
448
2harvests
117
1485
1232
185
264
361
114
896
2harvests
102
1509
1217
152
315
338
104
03harvests
154
2564
3177
317
389
481
171
112
3harvests
157
2560
3317
347
387
507
170
224
3harvests
141
2477
3183
336
376
434
177
448
3harvests
154
2719
3084
342
384
451
180
896
3harvests
92
1676
2012
170
218
258
110
112
2-spN2harv
103
1123
1262
167
225
319
97
224
2-spN2harv
125
1265
1468
192
282
404
108
448
2-spN2harv
107
1212
1350
185
232
353
98
896
2-spN2harv
106
1419
1490
164
260
325
101
112
3-spN3harv
139
2238
2762
280
346
418
154
224
3-spN3harv
120
2194
2474
268
281
361
145
448
3-spN3harv
144
2504
3053
336
338
441
178
896
3-spN3harv
112
2013
2427
259
253
297
134
SED
14
235
333
32
49
51
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1213
ORDER REPRINTS
uptake of 240 kgNha1 was highest for two harvests (scheduled for
three) and April fertilization (Table 6) Potassium uptake was highest
with multiple harvests The lack of the final harvest for this data set
severely limited interpretation
Perkins
Yields in 1998 were lower than those at Chickasha due to sandier
soil and less total rainfall Treatment combinations with two or three
harvests and split N applications produced the highest yields averaging
over 11Mgha1 Forage nitrogen concentration did not increase
with increasing yields as was the trend over all years (Fig 1) Potassium
uptake was maximized with two harvests and either one or two N
applications both averaging near 180 kgKha1 Uptake of P was
significantly affected by N rate and was greatest with one harvest and
one N application date at 174 kg ha1 (Table 7) Phosphorus uptake
decreased with multiple harvestsPerkins again produced much lower yields than Chickasha in 1999
and significant differences were noted due to number of harvests and N
timing (Table 8) Average yields were highest for the three harvests three-
way split N treatments (Table 8) Multiple harvests increased crop N
uptake over those with the same total N rates and one harvest Potassium
uptake was high for all multiple harvest plots In fact one harvest
0
05
1
15
2
25
3
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
KN
y = 00002x - 16581 R2= 07749
y = 5E-05x + 04825 R2= 02171
Figure 1 N and K concentrations with increasing dry biomass yields Chickasha
and Perkins (View this art in color at wwwdekkercom)
1214 Thomason et al
ORDER REPRINTS
removed little more than half of the K of two or three harvests (775 vs1552 kg ha1) Three harvests also resulted in increased P uptake
Dry matter yield in 2000 averaged over N rate was 133Mgha1
(Table 9) Nitrogen removal was maximized with three harvests andsplitting N into three applications (Table 9) There was a trend towardincreased N uptake with increasing harvest frequency and increasing Nrate Three harvests with N split into three increments resulted in 48more K uptake than two harvests and two N application dates (896 vs1844 kg ha1) The highest average P uptake was found for three harvestsand three-way split N applications (202 kg ha1) (Table 9)
Soil Carbon
Organic C data from in crown and between crown samples werecompared to organic C from initial samples from the area to determine ifchanges had occurred Bulk density measurements taken from theexperimental area did not differ from an adjacent area that wasconventionally tilled Initial samples indicated average soil organic C(SOC) for the site of 68 and 82mg g1 for Perkins and Chickasharespectively These results are possibly confounded by known spatialvariability in SOC reported by Raun et al[21] Contrast comparisons founda significant linear decrease in SOC with increasing N rates and twoharvests for the Chickasha crown sampling (Table 10) A significantquadratic increase was noted for Perkins in crown samples and asignificant quadratic decrease in SOC with increasing N rate was foundfor between crown samples at Chickasha Taken together there seem to beno obvious trends toward increasing or decreasing SOC at either site Thisis potentially influenced by the fact that aboveground biomass wasremoved from the site Garten and Wullschleger[22] have estimated that itmay take a decade of switchgrass production to sequester a significantmeasurable amount of soil carbon Given more time SOC may increasebut the short duration (3ndash5 yrs) of this study has provided no real evidencesupporting this increase in SOC especially in the lsquolsquobetween crownrsquorsquosamples
CONCLUSIONS
Overall forage K concentrations increased with increasing yieldwhile N concentrations were not affected (Fig 1) This suggests anincreased likelihood of obtaining a response to K rather than N in
Switchgrass Response to Applied Nitrogen 1215
ORDER REPRINTS
Table
7
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
273649
35478
70045
b2962
b18430
b2215
a151
Cutting
239889
137708
102599
b392
18
1398
56
Ntiming
31062
151319
7734
76
4818
105
14
Nrate
3118782
a202660
47764
157
a1925
1045
184
CuttingaN
rate
850489
92751
21729
a164
2875
1466
165
NtimingaN
rate
622391
217859
21916
189
3453
1344
161
Residualerror
44
28679
173477
12329
94
2004
620
112
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
106
1889
972
162
442
261
147
112
1harvest
84
1239
1058
136
577
268
124
224
1harvest
102
1812
1033
173
448
276
145
448
1harvest
119
1970
1530
177
535
326
166
896
1harvest
104
2349
1840
222
522
323
178
02harvests
87
1110
1283
112
330
257
110
112
2harvests
103
1596
1662
139
534
350
147
1216 Thomason et al
ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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ORDER REPRINTS
Table
4
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2996539
a87600
205053
a636
9278
15536
1010
Cutting
2372035
414096
a653177
b1024
1009
1563
266
Ntiming
3576196
111018
185774
a936
4895
6344
804
Nrate
3811575
a33003
62676
a527
a4584
a5872
336
a
CuttingaN
rate
8239068
59376
64205
400
6028
10433
560
NtimingaN
rate
6168684
34597
43532
180
2624
7172
282
Residualerror
44
220581
50460
52109
412
3338
4005
318
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
166
2048
1902
221
689
592
180
112
1harvest
141
1780
1875
195
601
638
164
224
1harvest
158
2127
2119
207
698
668
183
448
1harvest
172
2170
2212
211
726
747
200
896
1harvest
100
1328
1256
117
434
430
114
02harvests
166
2232
2468
225
677
776
205
112
2harvests
112
1548
1610
169
436
438
124
224
2harvests
226
3000
3378
311
910
1046
277
1208 Thomason et al
ORDER REPRINTS
448
2harvests
147
1956
1855
187
309
300
98
896
2harvests
162
2265
2241
191
575
680
190
03harvests
215
3403
3473
280
671
819
228
112
3harvests
168
2352
2705
201
533
658
184
224
3harvests
205
2833
3432
253
616
716
205
448
3harvests
245
3756
3864
289
641
668
190
896
3harvests
147
2229
2377
189
487
537
165
112
2-spN2harv
175
2119
2455
247
614
757
213
224
2-spN2harv
200
2677
3123
289
777
846
258
448
2-spN2harv
158
2070
2464
212
601
725
200
896
2-spN2harv
156
2355
2207
220
621
609
201
112
3-spN3harv
141
1962
2110
164
425
522
140
224
3-spN3harv
146
2233
2228
183
520
567
169
448
3-spN3harv
175
2375
2739
219
531
619
172
896
3-spN3harv
135
2210
2376
172
463
534
162
SED
12
580
589
52
149
163
46
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1209
ORDER REPRINTS
Table
5
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2464423
865906
1102070
a13008
a1665
6961
a291
Cutting
245101
952918
a1038877
b14290
b139
209
2203
b
Ntiming
3120137
133208
134666
1091
3230
2274
789
a
Nrate
32430687
717517
596007
4215
1799
2500
102
CuttingaN
rate
8207490
28101
43658
250
4465
b4667
a380
NtimingaN
rate
62060595
493140
380903
3444
810
1207
159
Residualerror
44
1562737
391299
334675
3504
1491
1808
291
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
109
781
1011
124
328
380
93
112
1harvest
150
1577
1541
171
478
532
145
224
1harvest
162
1459
1954
189
436
581
131
448
1harvest
191
1800
2386
181
693
715
180
896
1harvest
114
1257
1095
104
345
363
98
02harvests
179
2278
2736
274
543
602
192
112
2harvests
132
1754
2237
211
416
432
149
224
2harvests
170
2210
2453
244
530
614
182
1210 Thomason et al
ORDER REPRINTS
448
2harvests
162
2172
2291
221
352
400
120
896
2harvests
173
2474
2514
216
534
584
180
03harvests
200
2750
3273
352
500
559
205
112
3harvests
185
3150
3450
379
533
515
249
224
3harvests
167
2787
3303
335
392
436
184
448
3harvests
191
3300
3491
368
480
530
207
896
3harvests
154
2857
3000
331
431
472
194
112
2-spN2harv
145
1794
2258
226
432
469
156
224
2-spN2harv
146
1808
2078
223
564
501
195
448
2-spN2harv
175
2181
2713
248
487
557
171
896
2-spN2harv
208
2702
3557
288
654
703
220
112
3-spN3harv
155
2220
2522
260
353
381
145
224
3-spN3harv
152
2501
2949
304
412
401
174
448
3-spN3harv
180
2707
3137
354
405
475
170
896
3-spN3harv
263
3328
3144
425
366
401
167
SED
102
1573
1494
153
100
110
38
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1211
ORDER REPRINTS
Table
6
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2194823
b35769
a23391
1497
b1151
2969
b240
a
Cutting
2325370
b727339
b1445641
b9451
b2978
b1602
769
b
Ntiming
318979
a10279
15723
60
663
380
28
Nrate
3131730
b13237
24928
765
344
1865
a124
CuttingaN
rate
874236
a32484
a29096
491
1268
a1213
105
NtimingaN
rate
629574
7762
26341
384
237
239
41
Residualerror
44
31244
8263
16602
157
352
385
52
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
mdashmdash
mdashmdash
mdashmdash
mdash
112
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
224
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
448
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
896
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
02harvests
140
1493
1923
217
320
439
132
112
2harvests
110
1252
1516
203
264
345
106
224
2harvests
125
1334
1942
193
277
418
109
1212 Thomason et al
ORDER REPRINTS
448
2harvests
117
1485
1232
185
264
361
114
896
2harvests
102
1509
1217
152
315
338
104
03harvests
154
2564
3177
317
389
481
171
112
3harvests
157
2560
3317
347
387
507
170
224
3harvests
141
2477
3183
336
376
434
177
448
3harvests
154
2719
3084
342
384
451
180
896
3harvests
92
1676
2012
170
218
258
110
112
2-spN2harv
103
1123
1262
167
225
319
97
224
2-spN2harv
125
1265
1468
192
282
404
108
448
2-spN2harv
107
1212
1350
185
232
353
98
896
2-spN2harv
106
1419
1490
164
260
325
101
112
3-spN3harv
139
2238
2762
280
346
418
154
224
3-spN3harv
120
2194
2474
268
281
361
145
448
3-spN3harv
144
2504
3053
336
338
441
178
896
3-spN3harv
112
2013
2427
259
253
297
134
SED
14
235
333
32
49
51
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1213
ORDER REPRINTS
uptake of 240 kgNha1 was highest for two harvests (scheduled for
three) and April fertilization (Table 6) Potassium uptake was highest
with multiple harvests The lack of the final harvest for this data set
severely limited interpretation
Perkins
Yields in 1998 were lower than those at Chickasha due to sandier
soil and less total rainfall Treatment combinations with two or three
harvests and split N applications produced the highest yields averaging
over 11Mgha1 Forage nitrogen concentration did not increase
with increasing yields as was the trend over all years (Fig 1) Potassium
uptake was maximized with two harvests and either one or two N
applications both averaging near 180 kgKha1 Uptake of P was
significantly affected by N rate and was greatest with one harvest and
one N application date at 174 kg ha1 (Table 7) Phosphorus uptake
decreased with multiple harvestsPerkins again produced much lower yields than Chickasha in 1999
and significant differences were noted due to number of harvests and N
timing (Table 8) Average yields were highest for the three harvests three-
way split N treatments (Table 8) Multiple harvests increased crop N
uptake over those with the same total N rates and one harvest Potassium
uptake was high for all multiple harvest plots In fact one harvest
0
05
1
15
2
25
3
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
KN
y = 00002x - 16581 R2= 07749
y = 5E-05x + 04825 R2= 02171
Figure 1 N and K concentrations with increasing dry biomass yields Chickasha
and Perkins (View this art in color at wwwdekkercom)
1214 Thomason et al
ORDER REPRINTS
removed little more than half of the K of two or three harvests (775 vs1552 kg ha1) Three harvests also resulted in increased P uptake
Dry matter yield in 2000 averaged over N rate was 133Mgha1
(Table 9) Nitrogen removal was maximized with three harvests andsplitting N into three applications (Table 9) There was a trend towardincreased N uptake with increasing harvest frequency and increasing Nrate Three harvests with N split into three increments resulted in 48more K uptake than two harvests and two N application dates (896 vs1844 kg ha1) The highest average P uptake was found for three harvestsand three-way split N applications (202 kg ha1) (Table 9)
Soil Carbon
Organic C data from in crown and between crown samples werecompared to organic C from initial samples from the area to determine ifchanges had occurred Bulk density measurements taken from theexperimental area did not differ from an adjacent area that wasconventionally tilled Initial samples indicated average soil organic C(SOC) for the site of 68 and 82mg g1 for Perkins and Chickasharespectively These results are possibly confounded by known spatialvariability in SOC reported by Raun et al[21] Contrast comparisons founda significant linear decrease in SOC with increasing N rates and twoharvests for the Chickasha crown sampling (Table 10) A significantquadratic increase was noted for Perkins in crown samples and asignificant quadratic decrease in SOC with increasing N rate was foundfor between crown samples at Chickasha Taken together there seem to beno obvious trends toward increasing or decreasing SOC at either site Thisis potentially influenced by the fact that aboveground biomass wasremoved from the site Garten and Wullschleger[22] have estimated that itmay take a decade of switchgrass production to sequester a significantmeasurable amount of soil carbon Given more time SOC may increasebut the short duration (3ndash5 yrs) of this study has provided no real evidencesupporting this increase in SOC especially in the lsquolsquobetween crownrsquorsquosamples
CONCLUSIONS
Overall forage K concentrations increased with increasing yieldwhile N concentrations were not affected (Fig 1) This suggests anincreased likelihood of obtaining a response to K rather than N in
Switchgrass Response to Applied Nitrogen 1215
ORDER REPRINTS
Table
7
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
273649
35478
70045
b2962
b18430
b2215
a151
Cutting
239889
137708
102599
b392
18
1398
56
Ntiming
31062
151319
7734
76
4818
105
14
Nrate
3118782
a202660
47764
157
a1925
1045
184
CuttingaN
rate
850489
92751
21729
a164
2875
1466
165
NtimingaN
rate
622391
217859
21916
189
3453
1344
161
Residualerror
44
28679
173477
12329
94
2004
620
112
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
106
1889
972
162
442
261
147
112
1harvest
84
1239
1058
136
577
268
124
224
1harvest
102
1812
1033
173
448
276
145
448
1harvest
119
1970
1530
177
535
326
166
896
1harvest
104
2349
1840
222
522
323
178
02harvests
87
1110
1283
112
330
257
110
112
2harvests
103
1596
1662
139
534
350
147
1216 Thomason et al
ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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ORDER REPRINTS
448
2harvests
147
1956
1855
187
309
300
98
896
2harvests
162
2265
2241
191
575
680
190
03harvests
215
3403
3473
280
671
819
228
112
3harvests
168
2352
2705
201
533
658
184
224
3harvests
205
2833
3432
253
616
716
205
448
3harvests
245
3756
3864
289
641
668
190
896
3harvests
147
2229
2377
189
487
537
165
112
2-spN2harv
175
2119
2455
247
614
757
213
224
2-spN2harv
200
2677
3123
289
777
846
258
448
2-spN2harv
158
2070
2464
212
601
725
200
896
2-spN2harv
156
2355
2207
220
621
609
201
112
3-spN3harv
141
1962
2110
164
425
522
140
224
3-spN3harv
146
2233
2228
183
520
567
169
448
3-spN3harv
175
2375
2739
219
531
619
172
896
3-spN3harv
135
2210
2376
172
463
534
162
SED
12
580
589
52
149
163
46
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1209
ORDER REPRINTS
Table
5
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2464423
865906
1102070
a13008
a1665
6961
a291
Cutting
245101
952918
a1038877
b14290
b139
209
2203
b
Ntiming
3120137
133208
134666
1091
3230
2274
789
a
Nrate
32430687
717517
596007
4215
1799
2500
102
CuttingaN
rate
8207490
28101
43658
250
4465
b4667
a380
NtimingaN
rate
62060595
493140
380903
3444
810
1207
159
Residualerror
44
1562737
391299
334675
3504
1491
1808
291
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
109
781
1011
124
328
380
93
112
1harvest
150
1577
1541
171
478
532
145
224
1harvest
162
1459
1954
189
436
581
131
448
1harvest
191
1800
2386
181
693
715
180
896
1harvest
114
1257
1095
104
345
363
98
02harvests
179
2278
2736
274
543
602
192
112
2harvests
132
1754
2237
211
416
432
149
224
2harvests
170
2210
2453
244
530
614
182
1210 Thomason et al
ORDER REPRINTS
448
2harvests
162
2172
2291
221
352
400
120
896
2harvests
173
2474
2514
216
534
584
180
03harvests
200
2750
3273
352
500
559
205
112
3harvests
185
3150
3450
379
533
515
249
224
3harvests
167
2787
3303
335
392
436
184
448
3harvests
191
3300
3491
368
480
530
207
896
3harvests
154
2857
3000
331
431
472
194
112
2-spN2harv
145
1794
2258
226
432
469
156
224
2-spN2harv
146
1808
2078
223
564
501
195
448
2-spN2harv
175
2181
2713
248
487
557
171
896
2-spN2harv
208
2702
3557
288
654
703
220
112
3-spN3harv
155
2220
2522
260
353
381
145
224
3-spN3harv
152
2501
2949
304
412
401
174
448
3-spN3harv
180
2707
3137
354
405
475
170
896
3-spN3harv
263
3328
3144
425
366
401
167
SED
102
1573
1494
153
100
110
38
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1211
ORDER REPRINTS
Table
6
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2194823
b35769
a23391
1497
b1151
2969
b240
a
Cutting
2325370
b727339
b1445641
b9451
b2978
b1602
769
b
Ntiming
318979
a10279
15723
60
663
380
28
Nrate
3131730
b13237
24928
765
344
1865
a124
CuttingaN
rate
874236
a32484
a29096
491
1268
a1213
105
NtimingaN
rate
629574
7762
26341
384
237
239
41
Residualerror
44
31244
8263
16602
157
352
385
52
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
mdashmdash
mdashmdash
mdashmdash
mdash
112
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
224
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
448
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
896
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
02harvests
140
1493
1923
217
320
439
132
112
2harvests
110
1252
1516
203
264
345
106
224
2harvests
125
1334
1942
193
277
418
109
1212 Thomason et al
ORDER REPRINTS
448
2harvests
117
1485
1232
185
264
361
114
896
2harvests
102
1509
1217
152
315
338
104
03harvests
154
2564
3177
317
389
481
171
112
3harvests
157
2560
3317
347
387
507
170
224
3harvests
141
2477
3183
336
376
434
177
448
3harvests
154
2719
3084
342
384
451
180
896
3harvests
92
1676
2012
170
218
258
110
112
2-spN2harv
103
1123
1262
167
225
319
97
224
2-spN2harv
125
1265
1468
192
282
404
108
448
2-spN2harv
107
1212
1350
185
232
353
98
896
2-spN2harv
106
1419
1490
164
260
325
101
112
3-spN3harv
139
2238
2762
280
346
418
154
224
3-spN3harv
120
2194
2474
268
281
361
145
448
3-spN3harv
144
2504
3053
336
338
441
178
896
3-spN3harv
112
2013
2427
259
253
297
134
SED
14
235
333
32
49
51
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1213
ORDER REPRINTS
uptake of 240 kgNha1 was highest for two harvests (scheduled for
three) and April fertilization (Table 6) Potassium uptake was highest
with multiple harvests The lack of the final harvest for this data set
severely limited interpretation
Perkins
Yields in 1998 were lower than those at Chickasha due to sandier
soil and less total rainfall Treatment combinations with two or three
harvests and split N applications produced the highest yields averaging
over 11Mgha1 Forage nitrogen concentration did not increase
with increasing yields as was the trend over all years (Fig 1) Potassium
uptake was maximized with two harvests and either one or two N
applications both averaging near 180 kgKha1 Uptake of P was
significantly affected by N rate and was greatest with one harvest and
one N application date at 174 kg ha1 (Table 7) Phosphorus uptake
decreased with multiple harvestsPerkins again produced much lower yields than Chickasha in 1999
and significant differences were noted due to number of harvests and N
timing (Table 8) Average yields were highest for the three harvests three-
way split N treatments (Table 8) Multiple harvests increased crop N
uptake over those with the same total N rates and one harvest Potassium
uptake was high for all multiple harvest plots In fact one harvest
0
05
1
15
2
25
3
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
KN
y = 00002x - 16581 R2= 07749
y = 5E-05x + 04825 R2= 02171
Figure 1 N and K concentrations with increasing dry biomass yields Chickasha
and Perkins (View this art in color at wwwdekkercom)
1214 Thomason et al
ORDER REPRINTS
removed little more than half of the K of two or three harvests (775 vs1552 kg ha1) Three harvests also resulted in increased P uptake
Dry matter yield in 2000 averaged over N rate was 133Mgha1
(Table 9) Nitrogen removal was maximized with three harvests andsplitting N into three applications (Table 9) There was a trend towardincreased N uptake with increasing harvest frequency and increasing Nrate Three harvests with N split into three increments resulted in 48more K uptake than two harvests and two N application dates (896 vs1844 kg ha1) The highest average P uptake was found for three harvestsand three-way split N applications (202 kg ha1) (Table 9)
Soil Carbon
Organic C data from in crown and between crown samples werecompared to organic C from initial samples from the area to determine ifchanges had occurred Bulk density measurements taken from theexperimental area did not differ from an adjacent area that wasconventionally tilled Initial samples indicated average soil organic C(SOC) for the site of 68 and 82mg g1 for Perkins and Chickasharespectively These results are possibly confounded by known spatialvariability in SOC reported by Raun et al[21] Contrast comparisons founda significant linear decrease in SOC with increasing N rates and twoharvests for the Chickasha crown sampling (Table 10) A significantquadratic increase was noted for Perkins in crown samples and asignificant quadratic decrease in SOC with increasing N rate was foundfor between crown samples at Chickasha Taken together there seem to beno obvious trends toward increasing or decreasing SOC at either site Thisis potentially influenced by the fact that aboveground biomass wasremoved from the site Garten and Wullschleger[22] have estimated that itmay take a decade of switchgrass production to sequester a significantmeasurable amount of soil carbon Given more time SOC may increasebut the short duration (3ndash5 yrs) of this study has provided no real evidencesupporting this increase in SOC especially in the lsquolsquobetween crownrsquorsquosamples
CONCLUSIONS
Overall forage K concentrations increased with increasing yieldwhile N concentrations were not affected (Fig 1) This suggests anincreased likelihood of obtaining a response to K rather than N in
Switchgrass Response to Applied Nitrogen 1215
ORDER REPRINTS
Table
7
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
273649
35478
70045
b2962
b18430
b2215
a151
Cutting
239889
137708
102599
b392
18
1398
56
Ntiming
31062
151319
7734
76
4818
105
14
Nrate
3118782
a202660
47764
157
a1925
1045
184
CuttingaN
rate
850489
92751
21729
a164
2875
1466
165
NtimingaN
rate
622391
217859
21916
189
3453
1344
161
Residualerror
44
28679
173477
12329
94
2004
620
112
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
106
1889
972
162
442
261
147
112
1harvest
84
1239
1058
136
577
268
124
224
1harvest
102
1812
1033
173
448
276
145
448
1harvest
119
1970
1530
177
535
326
166
896
1harvest
104
2349
1840
222
522
323
178
02harvests
87
1110
1283
112
330
257
110
112
2harvests
103
1596
1662
139
534
350
147
1216 Thomason et al
ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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ORDER REPRINTS
Table
5
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2464423
865906
1102070
a13008
a1665
6961
a291
Cutting
245101
952918
a1038877
b14290
b139
209
2203
b
Ntiming
3120137
133208
134666
1091
3230
2274
789
a
Nrate
32430687
717517
596007
4215
1799
2500
102
CuttingaN
rate
8207490
28101
43658
250
4465
b4667
a380
NtimingaN
rate
62060595
493140
380903
3444
810
1207
159
Residualerror
44
1562737
391299
334675
3504
1491
1808
291
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
109
781
1011
124
328
380
93
112
1harvest
150
1577
1541
171
478
532
145
224
1harvest
162
1459
1954
189
436
581
131
448
1harvest
191
1800
2386
181
693
715
180
896
1harvest
114
1257
1095
104
345
363
98
02harvests
179
2278
2736
274
543
602
192
112
2harvests
132
1754
2237
211
416
432
149
224
2harvests
170
2210
2453
244
530
614
182
1210 Thomason et al
ORDER REPRINTS
448
2harvests
162
2172
2291
221
352
400
120
896
2harvests
173
2474
2514
216
534
584
180
03harvests
200
2750
3273
352
500
559
205
112
3harvests
185
3150
3450
379
533
515
249
224
3harvests
167
2787
3303
335
392
436
184
448
3harvests
191
3300
3491
368
480
530
207
896
3harvests
154
2857
3000
331
431
472
194
112
2-spN2harv
145
1794
2258
226
432
469
156
224
2-spN2harv
146
1808
2078
223
564
501
195
448
2-spN2harv
175
2181
2713
248
487
557
171
896
2-spN2harv
208
2702
3557
288
654
703
220
112
3-spN3harv
155
2220
2522
260
353
381
145
224
3-spN3harv
152
2501
2949
304
412
401
174
448
3-spN3harv
180
2707
3137
354
405
475
170
896
3-spN3harv
263
3328
3144
425
366
401
167
SED
102
1573
1494
153
100
110
38
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1211
ORDER REPRINTS
Table
6
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2194823
b35769
a23391
1497
b1151
2969
b240
a
Cutting
2325370
b727339
b1445641
b9451
b2978
b1602
769
b
Ntiming
318979
a10279
15723
60
663
380
28
Nrate
3131730
b13237
24928
765
344
1865
a124
CuttingaN
rate
874236
a32484
a29096
491
1268
a1213
105
NtimingaN
rate
629574
7762
26341
384
237
239
41
Residualerror
44
31244
8263
16602
157
352
385
52
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
mdashmdash
mdashmdash
mdashmdash
mdash
112
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
224
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
448
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
896
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
02harvests
140
1493
1923
217
320
439
132
112
2harvests
110
1252
1516
203
264
345
106
224
2harvests
125
1334
1942
193
277
418
109
1212 Thomason et al
ORDER REPRINTS
448
2harvests
117
1485
1232
185
264
361
114
896
2harvests
102
1509
1217
152
315
338
104
03harvests
154
2564
3177
317
389
481
171
112
3harvests
157
2560
3317
347
387
507
170
224
3harvests
141
2477
3183
336
376
434
177
448
3harvests
154
2719
3084
342
384
451
180
896
3harvests
92
1676
2012
170
218
258
110
112
2-spN2harv
103
1123
1262
167
225
319
97
224
2-spN2harv
125
1265
1468
192
282
404
108
448
2-spN2harv
107
1212
1350
185
232
353
98
896
2-spN2harv
106
1419
1490
164
260
325
101
112
3-spN3harv
139
2238
2762
280
346
418
154
224
3-spN3harv
120
2194
2474
268
281
361
145
448
3-spN3harv
144
2504
3053
336
338
441
178
896
3-spN3harv
112
2013
2427
259
253
297
134
SED
14
235
333
32
49
51
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1213
ORDER REPRINTS
uptake of 240 kgNha1 was highest for two harvests (scheduled for
three) and April fertilization (Table 6) Potassium uptake was highest
with multiple harvests The lack of the final harvest for this data set
severely limited interpretation
Perkins
Yields in 1998 were lower than those at Chickasha due to sandier
soil and less total rainfall Treatment combinations with two or three
harvests and split N applications produced the highest yields averaging
over 11Mgha1 Forage nitrogen concentration did not increase
with increasing yields as was the trend over all years (Fig 1) Potassium
uptake was maximized with two harvests and either one or two N
applications both averaging near 180 kgKha1 Uptake of P was
significantly affected by N rate and was greatest with one harvest and
one N application date at 174 kg ha1 (Table 7) Phosphorus uptake
decreased with multiple harvestsPerkins again produced much lower yields than Chickasha in 1999
and significant differences were noted due to number of harvests and N
timing (Table 8) Average yields were highest for the three harvests three-
way split N treatments (Table 8) Multiple harvests increased crop N
uptake over those with the same total N rates and one harvest Potassium
uptake was high for all multiple harvest plots In fact one harvest
0
05
1
15
2
25
3
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
KN
y = 00002x - 16581 R2= 07749
y = 5E-05x + 04825 R2= 02171
Figure 1 N and K concentrations with increasing dry biomass yields Chickasha
and Perkins (View this art in color at wwwdekkercom)
1214 Thomason et al
ORDER REPRINTS
removed little more than half of the K of two or three harvests (775 vs1552 kg ha1) Three harvests also resulted in increased P uptake
Dry matter yield in 2000 averaged over N rate was 133Mgha1
(Table 9) Nitrogen removal was maximized with three harvests andsplitting N into three applications (Table 9) There was a trend towardincreased N uptake with increasing harvest frequency and increasing Nrate Three harvests with N split into three increments resulted in 48more K uptake than two harvests and two N application dates (896 vs1844 kg ha1) The highest average P uptake was found for three harvestsand three-way split N applications (202 kg ha1) (Table 9)
Soil Carbon
Organic C data from in crown and between crown samples werecompared to organic C from initial samples from the area to determine ifchanges had occurred Bulk density measurements taken from theexperimental area did not differ from an adjacent area that wasconventionally tilled Initial samples indicated average soil organic C(SOC) for the site of 68 and 82mg g1 for Perkins and Chickasharespectively These results are possibly confounded by known spatialvariability in SOC reported by Raun et al[21] Contrast comparisons founda significant linear decrease in SOC with increasing N rates and twoharvests for the Chickasha crown sampling (Table 10) A significantquadratic increase was noted for Perkins in crown samples and asignificant quadratic decrease in SOC with increasing N rate was foundfor between crown samples at Chickasha Taken together there seem to beno obvious trends toward increasing or decreasing SOC at either site Thisis potentially influenced by the fact that aboveground biomass wasremoved from the site Garten and Wullschleger[22] have estimated that itmay take a decade of switchgrass production to sequester a significantmeasurable amount of soil carbon Given more time SOC may increasebut the short duration (3ndash5 yrs) of this study has provided no real evidencesupporting this increase in SOC especially in the lsquolsquobetween crownrsquorsquosamples
CONCLUSIONS
Overall forage K concentrations increased with increasing yieldwhile N concentrations were not affected (Fig 1) This suggests anincreased likelihood of obtaining a response to K rather than N in
Switchgrass Response to Applied Nitrogen 1215
ORDER REPRINTS
Table
7
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
273649
35478
70045
b2962
b18430
b2215
a151
Cutting
239889
137708
102599
b392
18
1398
56
Ntiming
31062
151319
7734
76
4818
105
14
Nrate
3118782
a202660
47764
157
a1925
1045
184
CuttingaN
rate
850489
92751
21729
a164
2875
1466
165
NtimingaN
rate
622391
217859
21916
189
3453
1344
161
Residualerror
44
28679
173477
12329
94
2004
620
112
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
106
1889
972
162
442
261
147
112
1harvest
84
1239
1058
136
577
268
124
224
1harvest
102
1812
1033
173
448
276
145
448
1harvest
119
1970
1530
177
535
326
166
896
1harvest
104
2349
1840
222
522
323
178
02harvests
87
1110
1283
112
330
257
110
112
2harvests
103
1596
1662
139
534
350
147
1216 Thomason et al
ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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ORDER REPRINTS
448
2harvests
162
2172
2291
221
352
400
120
896
2harvests
173
2474
2514
216
534
584
180
03harvests
200
2750
3273
352
500
559
205
112
3harvests
185
3150
3450
379
533
515
249
224
3harvests
167
2787
3303
335
392
436
184
448
3harvests
191
3300
3491
368
480
530
207
896
3harvests
154
2857
3000
331
431
472
194
112
2-spN2harv
145
1794
2258
226
432
469
156
224
2-spN2harv
146
1808
2078
223
564
501
195
448
2-spN2harv
175
2181
2713
248
487
557
171
896
2-spN2harv
208
2702
3557
288
654
703
220
112
3-spN3harv
155
2220
2522
260
353
381
145
224
3-spN3harv
152
2501
2949
304
412
401
174
448
3-spN3harv
180
2707
3137
354
405
475
170
896
3-spN3harv
263
3328
3144
425
366
401
167
SED
102
1573
1494
153
100
110
38
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1211
ORDER REPRINTS
Table
6
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2194823
b35769
a23391
1497
b1151
2969
b240
a
Cutting
2325370
b727339
b1445641
b9451
b2978
b1602
769
b
Ntiming
318979
a10279
15723
60
663
380
28
Nrate
3131730
b13237
24928
765
344
1865
a124
CuttingaN
rate
874236
a32484
a29096
491
1268
a1213
105
NtimingaN
rate
629574
7762
26341
384
237
239
41
Residualerror
44
31244
8263
16602
157
352
385
52
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
mdashmdash
mdashmdash
mdashmdash
mdash
112
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
224
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
448
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
896
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
02harvests
140
1493
1923
217
320
439
132
112
2harvests
110
1252
1516
203
264
345
106
224
2harvests
125
1334
1942
193
277
418
109
1212 Thomason et al
ORDER REPRINTS
448
2harvests
117
1485
1232
185
264
361
114
896
2harvests
102
1509
1217
152
315
338
104
03harvests
154
2564
3177
317
389
481
171
112
3harvests
157
2560
3317
347
387
507
170
224
3harvests
141
2477
3183
336
376
434
177
448
3harvests
154
2719
3084
342
384
451
180
896
3harvests
92
1676
2012
170
218
258
110
112
2-spN2harv
103
1123
1262
167
225
319
97
224
2-spN2harv
125
1265
1468
192
282
404
108
448
2-spN2harv
107
1212
1350
185
232
353
98
896
2-spN2harv
106
1419
1490
164
260
325
101
112
3-spN3harv
139
2238
2762
280
346
418
154
224
3-spN3harv
120
2194
2474
268
281
361
145
448
3-spN3harv
144
2504
3053
336
338
441
178
896
3-spN3harv
112
2013
2427
259
253
297
134
SED
14
235
333
32
49
51
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1213
ORDER REPRINTS
uptake of 240 kgNha1 was highest for two harvests (scheduled for
three) and April fertilization (Table 6) Potassium uptake was highest
with multiple harvests The lack of the final harvest for this data set
severely limited interpretation
Perkins
Yields in 1998 were lower than those at Chickasha due to sandier
soil and less total rainfall Treatment combinations with two or three
harvests and split N applications produced the highest yields averaging
over 11Mgha1 Forage nitrogen concentration did not increase
with increasing yields as was the trend over all years (Fig 1) Potassium
uptake was maximized with two harvests and either one or two N
applications both averaging near 180 kgKha1 Uptake of P was
significantly affected by N rate and was greatest with one harvest and
one N application date at 174 kg ha1 (Table 7) Phosphorus uptake
decreased with multiple harvestsPerkins again produced much lower yields than Chickasha in 1999
and significant differences were noted due to number of harvests and N
timing (Table 8) Average yields were highest for the three harvests three-
way split N treatments (Table 8) Multiple harvests increased crop N
uptake over those with the same total N rates and one harvest Potassium
uptake was high for all multiple harvest plots In fact one harvest
0
05
1
15
2
25
3
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
KN
y = 00002x - 16581 R2= 07749
y = 5E-05x + 04825 R2= 02171
Figure 1 N and K concentrations with increasing dry biomass yields Chickasha
and Perkins (View this art in color at wwwdekkercom)
1214 Thomason et al
ORDER REPRINTS
removed little more than half of the K of two or three harvests (775 vs1552 kg ha1) Three harvests also resulted in increased P uptake
Dry matter yield in 2000 averaged over N rate was 133Mgha1
(Table 9) Nitrogen removal was maximized with three harvests andsplitting N into three applications (Table 9) There was a trend towardincreased N uptake with increasing harvest frequency and increasing Nrate Three harvests with N split into three increments resulted in 48more K uptake than two harvests and two N application dates (896 vs1844 kg ha1) The highest average P uptake was found for three harvestsand three-way split N applications (202 kg ha1) (Table 9)
Soil Carbon
Organic C data from in crown and between crown samples werecompared to organic C from initial samples from the area to determine ifchanges had occurred Bulk density measurements taken from theexperimental area did not differ from an adjacent area that wasconventionally tilled Initial samples indicated average soil organic C(SOC) for the site of 68 and 82mg g1 for Perkins and Chickasharespectively These results are possibly confounded by known spatialvariability in SOC reported by Raun et al[21] Contrast comparisons founda significant linear decrease in SOC with increasing N rates and twoharvests for the Chickasha crown sampling (Table 10) A significantquadratic increase was noted for Perkins in crown samples and asignificant quadratic decrease in SOC with increasing N rate was foundfor between crown samples at Chickasha Taken together there seem to beno obvious trends toward increasing or decreasing SOC at either site Thisis potentially influenced by the fact that aboveground biomass wasremoved from the site Garten and Wullschleger[22] have estimated that itmay take a decade of switchgrass production to sequester a significantmeasurable amount of soil carbon Given more time SOC may increasebut the short duration (3ndash5 yrs) of this study has provided no real evidencesupporting this increase in SOC especially in the lsquolsquobetween crownrsquorsquosamples
CONCLUSIONS
Overall forage K concentrations increased with increasing yieldwhile N concentrations were not affected (Fig 1) This suggests anincreased likelihood of obtaining a response to K rather than N in
Switchgrass Response to Applied Nitrogen 1215
ORDER REPRINTS
Table
7
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
273649
35478
70045
b2962
b18430
b2215
a151
Cutting
239889
137708
102599
b392
18
1398
56
Ntiming
31062
151319
7734
76
4818
105
14
Nrate
3118782
a202660
47764
157
a1925
1045
184
CuttingaN
rate
850489
92751
21729
a164
2875
1466
165
NtimingaN
rate
622391
217859
21916
189
3453
1344
161
Residualerror
44
28679
173477
12329
94
2004
620
112
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
106
1889
972
162
442
261
147
112
1harvest
84
1239
1058
136
577
268
124
224
1harvest
102
1812
1033
173
448
276
145
448
1harvest
119
1970
1530
177
535
326
166
896
1harvest
104
2349
1840
222
522
323
178
02harvests
87
1110
1283
112
330
257
110
112
2harvests
103
1596
1662
139
534
350
147
1216 Thomason et al
ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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ORDER REPRINTS
Table
6
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyChickashaOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2194823
b35769
a23391
1497
b1151
2969
b240
a
Cutting
2325370
b727339
b1445641
b9451
b2978
b1602
769
b
Ntiming
318979
a10279
15723
60
663
380
28
Nrate
3131730
b13237
24928
765
344
1865
a124
CuttingaN
rate
874236
a32484
a29096
491
1268
a1213
105
NtimingaN
rate
629574
7762
26341
384
237
239
41
Residualerror
44
31244
8263
16602
157
352
385
52
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
mdashmdash
mdashmdash
mdashmdash
mdash
112
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
224
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
448
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
896
1harvest
mdashmdash
mdashmdash
mdashmdash
mdash
02harvests
140
1493
1923
217
320
439
132
112
2harvests
110
1252
1516
203
264
345
106
224
2harvests
125
1334
1942
193
277
418
109
1212 Thomason et al
ORDER REPRINTS
448
2harvests
117
1485
1232
185
264
361
114
896
2harvests
102
1509
1217
152
315
338
104
03harvests
154
2564
3177
317
389
481
171
112
3harvests
157
2560
3317
347
387
507
170
224
3harvests
141
2477
3183
336
376
434
177
448
3harvests
154
2719
3084
342
384
451
180
896
3harvests
92
1676
2012
170
218
258
110
112
2-spN2harv
103
1123
1262
167
225
319
97
224
2-spN2harv
125
1265
1468
192
282
404
108
448
2-spN2harv
107
1212
1350
185
232
353
98
896
2-spN2harv
106
1419
1490
164
260
325
101
112
3-spN3harv
139
2238
2762
280
346
418
154
224
3-spN3harv
120
2194
2474
268
281
361
145
448
3-spN3harv
144
2504
3053
336
338
441
178
896
3-spN3harv
112
2013
2427
259
253
297
134
SED
14
235
333
32
49
51
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1213
ORDER REPRINTS
uptake of 240 kgNha1 was highest for two harvests (scheduled for
three) and April fertilization (Table 6) Potassium uptake was highest
with multiple harvests The lack of the final harvest for this data set
severely limited interpretation
Perkins
Yields in 1998 were lower than those at Chickasha due to sandier
soil and less total rainfall Treatment combinations with two or three
harvests and split N applications produced the highest yields averaging
over 11Mgha1 Forage nitrogen concentration did not increase
with increasing yields as was the trend over all years (Fig 1) Potassium
uptake was maximized with two harvests and either one or two N
applications both averaging near 180 kgKha1 Uptake of P was
significantly affected by N rate and was greatest with one harvest and
one N application date at 174 kg ha1 (Table 7) Phosphorus uptake
decreased with multiple harvestsPerkins again produced much lower yields than Chickasha in 1999
and significant differences were noted due to number of harvests and N
timing (Table 8) Average yields were highest for the three harvests three-
way split N treatments (Table 8) Multiple harvests increased crop N
uptake over those with the same total N rates and one harvest Potassium
uptake was high for all multiple harvest plots In fact one harvest
0
05
1
15
2
25
3
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
KN
y = 00002x - 16581 R2= 07749
y = 5E-05x + 04825 R2= 02171
Figure 1 N and K concentrations with increasing dry biomass yields Chickasha
and Perkins (View this art in color at wwwdekkercom)
1214 Thomason et al
ORDER REPRINTS
removed little more than half of the K of two or three harvests (775 vs1552 kg ha1) Three harvests also resulted in increased P uptake
Dry matter yield in 2000 averaged over N rate was 133Mgha1
(Table 9) Nitrogen removal was maximized with three harvests andsplitting N into three applications (Table 9) There was a trend towardincreased N uptake with increasing harvest frequency and increasing Nrate Three harvests with N split into three increments resulted in 48more K uptake than two harvests and two N application dates (896 vs1844 kg ha1) The highest average P uptake was found for three harvestsand three-way split N applications (202 kg ha1) (Table 9)
Soil Carbon
Organic C data from in crown and between crown samples werecompared to organic C from initial samples from the area to determine ifchanges had occurred Bulk density measurements taken from theexperimental area did not differ from an adjacent area that wasconventionally tilled Initial samples indicated average soil organic C(SOC) for the site of 68 and 82mg g1 for Perkins and Chickasharespectively These results are possibly confounded by known spatialvariability in SOC reported by Raun et al[21] Contrast comparisons founda significant linear decrease in SOC with increasing N rates and twoharvests for the Chickasha crown sampling (Table 10) A significantquadratic increase was noted for Perkins in crown samples and asignificant quadratic decrease in SOC with increasing N rate was foundfor between crown samples at Chickasha Taken together there seem to beno obvious trends toward increasing or decreasing SOC at either site Thisis potentially influenced by the fact that aboveground biomass wasremoved from the site Garten and Wullschleger[22] have estimated that itmay take a decade of switchgrass production to sequester a significantmeasurable amount of soil carbon Given more time SOC may increasebut the short duration (3ndash5 yrs) of this study has provided no real evidencesupporting this increase in SOC especially in the lsquolsquobetween crownrsquorsquosamples
CONCLUSIONS
Overall forage K concentrations increased with increasing yieldwhile N concentrations were not affected (Fig 1) This suggests anincreased likelihood of obtaining a response to K rather than N in
Switchgrass Response to Applied Nitrogen 1215
ORDER REPRINTS
Table
7
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
273649
35478
70045
b2962
b18430
b2215
a151
Cutting
239889
137708
102599
b392
18
1398
56
Ntiming
31062
151319
7734
76
4818
105
14
Nrate
3118782
a202660
47764
157
a1925
1045
184
CuttingaN
rate
850489
92751
21729
a164
2875
1466
165
NtimingaN
rate
622391
217859
21916
189
3453
1344
161
Residualerror
44
28679
173477
12329
94
2004
620
112
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
106
1889
972
162
442
261
147
112
1harvest
84
1239
1058
136
577
268
124
224
1harvest
102
1812
1033
173
448
276
145
448
1harvest
119
1970
1530
177
535
326
166
896
1harvest
104
2349
1840
222
522
323
178
02harvests
87
1110
1283
112
330
257
110
112
2harvests
103
1596
1662
139
534
350
147
1216 Thomason et al
ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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ORDER REPRINTS
448
2harvests
117
1485
1232
185
264
361
114
896
2harvests
102
1509
1217
152
315
338
104
03harvests
154
2564
3177
317
389
481
171
112
3harvests
157
2560
3317
347
387
507
170
224
3harvests
141
2477
3183
336
376
434
177
448
3harvests
154
2719
3084
342
384
451
180
896
3harvests
92
1676
2012
170
218
258
110
112
2-spN2harv
103
1123
1262
167
225
319
97
224
2-spN2harv
125
1265
1468
192
282
404
108
448
2-spN2harv
107
1212
1350
185
232
353
98
896
2-spN2harv
106
1419
1490
164
260
325
101
112
3-spN3harv
139
2238
2762
280
346
418
154
224
3-spN3harv
120
2194
2474
268
281
361
145
448
3-spN3harv
144
2504
3053
336
338
441
178
896
3-spN3harv
112
2013
2427
259
253
297
134
SED
14
235
333
32
49
51
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1213
ORDER REPRINTS
uptake of 240 kgNha1 was highest for two harvests (scheduled for
three) and April fertilization (Table 6) Potassium uptake was highest
with multiple harvests The lack of the final harvest for this data set
severely limited interpretation
Perkins
Yields in 1998 were lower than those at Chickasha due to sandier
soil and less total rainfall Treatment combinations with two or three
harvests and split N applications produced the highest yields averaging
over 11Mgha1 Forage nitrogen concentration did not increase
with increasing yields as was the trend over all years (Fig 1) Potassium
uptake was maximized with two harvests and either one or two N
applications both averaging near 180 kgKha1 Uptake of P was
significantly affected by N rate and was greatest with one harvest and
one N application date at 174 kg ha1 (Table 7) Phosphorus uptake
decreased with multiple harvestsPerkins again produced much lower yields than Chickasha in 1999
and significant differences were noted due to number of harvests and N
timing (Table 8) Average yields were highest for the three harvests three-
way split N treatments (Table 8) Multiple harvests increased crop N
uptake over those with the same total N rates and one harvest Potassium
uptake was high for all multiple harvest plots In fact one harvest
0
05
1
15
2
25
3
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
KN
y = 00002x - 16581 R2= 07749
y = 5E-05x + 04825 R2= 02171
Figure 1 N and K concentrations with increasing dry biomass yields Chickasha
and Perkins (View this art in color at wwwdekkercom)
1214 Thomason et al
ORDER REPRINTS
removed little more than half of the K of two or three harvests (775 vs1552 kg ha1) Three harvests also resulted in increased P uptake
Dry matter yield in 2000 averaged over N rate was 133Mgha1
(Table 9) Nitrogen removal was maximized with three harvests andsplitting N into three applications (Table 9) There was a trend towardincreased N uptake with increasing harvest frequency and increasing Nrate Three harvests with N split into three increments resulted in 48more K uptake than two harvests and two N application dates (896 vs1844 kg ha1) The highest average P uptake was found for three harvestsand three-way split N applications (202 kg ha1) (Table 9)
Soil Carbon
Organic C data from in crown and between crown samples werecompared to organic C from initial samples from the area to determine ifchanges had occurred Bulk density measurements taken from theexperimental area did not differ from an adjacent area that wasconventionally tilled Initial samples indicated average soil organic C(SOC) for the site of 68 and 82mg g1 for Perkins and Chickasharespectively These results are possibly confounded by known spatialvariability in SOC reported by Raun et al[21] Contrast comparisons founda significant linear decrease in SOC with increasing N rates and twoharvests for the Chickasha crown sampling (Table 10) A significantquadratic increase was noted for Perkins in crown samples and asignificant quadratic decrease in SOC with increasing N rate was foundfor between crown samples at Chickasha Taken together there seem to beno obvious trends toward increasing or decreasing SOC at either site Thisis potentially influenced by the fact that aboveground biomass wasremoved from the site Garten and Wullschleger[22] have estimated that itmay take a decade of switchgrass production to sequester a significantmeasurable amount of soil carbon Given more time SOC may increasebut the short duration (3ndash5 yrs) of this study has provided no real evidencesupporting this increase in SOC especially in the lsquolsquobetween crownrsquorsquosamples
CONCLUSIONS
Overall forage K concentrations increased with increasing yieldwhile N concentrations were not affected (Fig 1) This suggests anincreased likelihood of obtaining a response to K rather than N in
Switchgrass Response to Applied Nitrogen 1215
ORDER REPRINTS
Table
7
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
273649
35478
70045
b2962
b18430
b2215
a151
Cutting
239889
137708
102599
b392
18
1398
56
Ntiming
31062
151319
7734
76
4818
105
14
Nrate
3118782
a202660
47764
157
a1925
1045
184
CuttingaN
rate
850489
92751
21729
a164
2875
1466
165
NtimingaN
rate
622391
217859
21916
189
3453
1344
161
Residualerror
44
28679
173477
12329
94
2004
620
112
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
106
1889
972
162
442
261
147
112
1harvest
84
1239
1058
136
577
268
124
224
1harvest
102
1812
1033
173
448
276
145
448
1harvest
119
1970
1530
177
535
326
166
896
1harvest
104
2349
1840
222
522
323
178
02harvests
87
1110
1283
112
330
257
110
112
2harvests
103
1596
1662
139
534
350
147
1216 Thomason et al
ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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ORDER REPRINTS
uptake of 240 kgNha1 was highest for two harvests (scheduled for
three) and April fertilization (Table 6) Potassium uptake was highest
with multiple harvests The lack of the final harvest for this data set
severely limited interpretation
Perkins
Yields in 1998 were lower than those at Chickasha due to sandier
soil and less total rainfall Treatment combinations with two or three
harvests and split N applications produced the highest yields averaging
over 11Mgha1 Forage nitrogen concentration did not increase
with increasing yields as was the trend over all years (Fig 1) Potassium
uptake was maximized with two harvests and either one or two N
applications both averaging near 180 kgKha1 Uptake of P was
significantly affected by N rate and was greatest with one harvest and
one N application date at 174 kg ha1 (Table 7) Phosphorus uptake
decreased with multiple harvestsPerkins again produced much lower yields than Chickasha in 1999
and significant differences were noted due to number of harvests and N
timing (Table 8) Average yields were highest for the three harvests three-
way split N treatments (Table 8) Multiple harvests increased crop N
uptake over those with the same total N rates and one harvest Potassium
uptake was high for all multiple harvest plots In fact one harvest
0
05
1
15
2
25
3
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
KN
y = 00002x - 16581 R2= 07749
y = 5E-05x + 04825 R2= 02171
Figure 1 N and K concentrations with increasing dry biomass yields Chickasha
and Perkins (View this art in color at wwwdekkercom)
1214 Thomason et al
ORDER REPRINTS
removed little more than half of the K of two or three harvests (775 vs1552 kg ha1) Three harvests also resulted in increased P uptake
Dry matter yield in 2000 averaged over N rate was 133Mgha1
(Table 9) Nitrogen removal was maximized with three harvests andsplitting N into three applications (Table 9) There was a trend towardincreased N uptake with increasing harvest frequency and increasing Nrate Three harvests with N split into three increments resulted in 48more K uptake than two harvests and two N application dates (896 vs1844 kg ha1) The highest average P uptake was found for three harvestsand three-way split N applications (202 kg ha1) (Table 9)
Soil Carbon
Organic C data from in crown and between crown samples werecompared to organic C from initial samples from the area to determine ifchanges had occurred Bulk density measurements taken from theexperimental area did not differ from an adjacent area that wasconventionally tilled Initial samples indicated average soil organic C(SOC) for the site of 68 and 82mg g1 for Perkins and Chickasharespectively These results are possibly confounded by known spatialvariability in SOC reported by Raun et al[21] Contrast comparisons founda significant linear decrease in SOC with increasing N rates and twoharvests for the Chickasha crown sampling (Table 10) A significantquadratic increase was noted for Perkins in crown samples and asignificant quadratic decrease in SOC with increasing N rate was foundfor between crown samples at Chickasha Taken together there seem to beno obvious trends toward increasing or decreasing SOC at either site Thisis potentially influenced by the fact that aboveground biomass wasremoved from the site Garten and Wullschleger[22] have estimated that itmay take a decade of switchgrass production to sequester a significantmeasurable amount of soil carbon Given more time SOC may increasebut the short duration (3ndash5 yrs) of this study has provided no real evidencesupporting this increase in SOC especially in the lsquolsquobetween crownrsquorsquosamples
CONCLUSIONS
Overall forage K concentrations increased with increasing yieldwhile N concentrations were not affected (Fig 1) This suggests anincreased likelihood of obtaining a response to K rather than N in
Switchgrass Response to Applied Nitrogen 1215
ORDER REPRINTS
Table
7
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
273649
35478
70045
b2962
b18430
b2215
a151
Cutting
239889
137708
102599
b392
18
1398
56
Ntiming
31062
151319
7734
76
4818
105
14
Nrate
3118782
a202660
47764
157
a1925
1045
184
CuttingaN
rate
850489
92751
21729
a164
2875
1466
165
NtimingaN
rate
622391
217859
21916
189
3453
1344
161
Residualerror
44
28679
173477
12329
94
2004
620
112
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
106
1889
972
162
442
261
147
112
1harvest
84
1239
1058
136
577
268
124
224
1harvest
102
1812
1033
173
448
276
145
448
1harvest
119
1970
1530
177
535
326
166
896
1harvest
104
2349
1840
222
522
323
178
02harvests
87
1110
1283
112
330
257
110
112
2harvests
103
1596
1662
139
534
350
147
1216 Thomason et al
ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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ORDER REPRINTS
removed little more than half of the K of two or three harvests (775 vs1552 kg ha1) Three harvests also resulted in increased P uptake
Dry matter yield in 2000 averaged over N rate was 133Mgha1
(Table 9) Nitrogen removal was maximized with three harvests andsplitting N into three applications (Table 9) There was a trend towardincreased N uptake with increasing harvest frequency and increasing Nrate Three harvests with N split into three increments resulted in 48more K uptake than two harvests and two N application dates (896 vs1844 kg ha1) The highest average P uptake was found for three harvestsand three-way split N applications (202 kg ha1) (Table 9)
Soil Carbon
Organic C data from in crown and between crown samples werecompared to organic C from initial samples from the area to determine ifchanges had occurred Bulk density measurements taken from theexperimental area did not differ from an adjacent area that wasconventionally tilled Initial samples indicated average soil organic C(SOC) for the site of 68 and 82mg g1 for Perkins and Chickasharespectively These results are possibly confounded by known spatialvariability in SOC reported by Raun et al[21] Contrast comparisons founda significant linear decrease in SOC with increasing N rates and twoharvests for the Chickasha crown sampling (Table 10) A significantquadratic increase was noted for Perkins in crown samples and asignificant quadratic decrease in SOC with increasing N rate was foundfor between crown samples at Chickasha Taken together there seem to beno obvious trends toward increasing or decreasing SOC at either site Thisis potentially influenced by the fact that aboveground biomass wasremoved from the site Garten and Wullschleger[22] have estimated that itmay take a decade of switchgrass production to sequester a significantmeasurable amount of soil carbon Given more time SOC may increasebut the short duration (3ndash5 yrs) of this study has provided no real evidencesupporting this increase in SOC especially in the lsquolsquobetween crownrsquorsquosamples
CONCLUSIONS
Overall forage K concentrations increased with increasing yieldwhile N concentrations were not affected (Fig 1) This suggests anincreased likelihood of obtaining a response to K rather than N in
Switchgrass Response to Applied Nitrogen 1215
ORDER REPRINTS
Table
7
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
273649
35478
70045
b2962
b18430
b2215
a151
Cutting
239889
137708
102599
b392
18
1398
56
Ntiming
31062
151319
7734
76
4818
105
14
Nrate
3118782
a202660
47764
157
a1925
1045
184
CuttingaN
rate
850489
92751
21729
a164
2875
1466
165
NtimingaN
rate
622391
217859
21916
189
3453
1344
161
Residualerror
44
28679
173477
12329
94
2004
620
112
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
106
1889
972
162
442
261
147
112
1harvest
84
1239
1058
136
577
268
124
224
1harvest
102
1812
1033
173
448
276
145
448
1harvest
119
1970
1530
177
535
326
166
896
1harvest
104
2349
1840
222
522
323
178
02harvests
87
1110
1283
112
330
257
110
112
2harvests
103
1596
1662
139
534
350
147
1216 Thomason et al
ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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ORDER REPRINTS
Table
7
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1998
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
273649
35478
70045
b2962
b18430
b2215
a151
Cutting
239889
137708
102599
b392
18
1398
56
Ntiming
31062
151319
7734
76
4818
105
14
Nrate
3118782
a202660
47764
157
a1925
1045
184
CuttingaN
rate
850489
92751
21729
a164
2875
1466
165
NtimingaN
rate
622391
217859
21916
189
3453
1344
161
Residualerror
44
28679
173477
12329
94
2004
620
112
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
106
1889
972
162
442
261
147
112
1harvest
84
1239
1058
136
577
268
124
224
1harvest
102
1812
1033
173
448
276
145
448
1harvest
119
1970
1530
177
535
326
166
896
1harvest
104
2349
1840
222
522
323
178
02harvests
87
1110
1283
112
330
257
110
112
2harvests
103
1596
1662
139
534
350
147
1216 Thomason et al
ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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ORDER REPRINTS
224
2harvests
133
2082
2177
177
608
471
188
448
2harvests
110
1874
1861
133
285
232
104
896
2harvests
109
2041
2085
154
685
416
170
03harvests
121
1677
1728
170
495
393
143
112
3harvests
111
1678
1523
129
431
366
131
224
3harvests
107
1767
1711
137
461
341
140
448
3harvests
124
2038
1620
135
400
318
136
896
3harvests
104
2166
1647
144
473
312
148
112
2-spN2harv
98
1282
1455
116
423
308
127
224
2-spN2harv
118
1713
1861
141
648
386
170
448
2-spN2harv
118
1861
1995
143
537
393
167
896
2-spN2harv
119
2183
1838
145
486
346
168
112
3-spN3harv
115
1868
1662
151
514
341
136
224
3-spN3harv
109
4933
1564
135
603
329
130
448
3-spN3harv
140
2101
2266
193
647
437
161
896
3-spN3harv
90
1530
1099
91
531
295
114
SED
14
1075
287
25
116
64
27
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1217
ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
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ORDER REPRINTS
Table
8
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK1999
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
230112
9728
57637
283
1049
244
24
Cutting
2111222
a130902
b262385
b1502
b2694
457
418
b
Ntiming
331828
a26761
b43367
b117
336
b204
b50
Nrate
371381
48248
b56927
b37
319
a1404
a122
CuttingaN
rate
836100
6973
15745
a105
536
178
27
NtimingaN
rate
631647
12428
8064
117
730
294
50
Residualerror
44
74364
16261
16948
134
990
432
79
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
70
379
494
85
197
123
44
112
1harvest
97
813
700
122
331
171
78
224
1harvest
72
684
614
71
232
159
60
448
1harvest
91
984
925
79
276
212
79
896
1harvest
105
1202
1142
82
316
237
92
02harvests
52
388
661
65
191
93
42
112
2harvests
88
804
1387
127
357
179
80
224
2harvests
103
1209
1819
136
321
249
98
1218 Thomason et al
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
Request PermissionOrder Reprints
Reprints of this article can also be ordered at
httpwwwdekkercomservletproductDOI101081PLN120038544
Request Permission or Order Reprints Instantly
Interested in copying and sharing this article In most cases US Copyright Law requires that you get permission from the articlersquos rightsholder before using copyrighted content
All information and materials found in this article including but not limited to text trademarks patents logos graphics and images (the Materials) are the copyrighted works and other forms of intellectual property of Marcel Dekker Inc or its licensors All rights not expressly granted are reserved
Get permission to lawfully reproduce and distribute the Materials or order reprints quickly and painlessly Simply click on the Request Permission Order Reprints link below and follow the instructions Visit the US Copyright Office for information on Fair Use limitations of US copyright law Please refer to The Association of American Publishersrsquo (AAP) website for guidelines on Fair Use in the Classroom
The Materials are for your personal use only and cannot be reformatted reposted resold or distributed by electronic means or otherwise without permission from Marcel Dekker Inc Marcel Dekker Inc grants you the limited right to display the Materials only on your personal computer or personal wireless device and to copy and download single copies of such Materials provided that any copyright trademark or other notice appearing on such Materials is also retained by displayed copied or downloaded as part of the Materials and is not removed or obscured and provided you do not edit modify alter or enhance the Materials Please refer to our Website User Agreement for more details
ORDER REPRINTS
448
2harvests
101
1255
1809
113
227
206
73
896
2harvests
120
1603
2083
119
344
266
108
03harvests
87
1019
1133
127
307
151
79
112
3harvests
96
1133
1476
152
365
211
101
224
3harvests
101
1258
1300
152
411
208
110
448
3harvests
107
1532
1505
148
341
238
100
896
3harvests
128
2058
1747
174
329
267
127
112
2-spN2harv
69
480
907
75
233
115
49
224
2-spN2harv
88
889
1309
108
310
198
78
448
2-spN2harv
99
1045
1554
109
322
256
89
896
2-spN2harv
119
1306
1900
133
345
269
102
112
3-spN3harv
104
986
1087
149
274
174
86
224
3-spN3harv
126
1608
1547
178
398
227
114
448
3-spN3harv
109
1531
1431
126
344
230
105
896
3-spN3harv
109
1434
1441
137
304
209
100
SED
22
329
114
30
81
54
23
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1219
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
Request PermissionOrder Reprints
Reprints of this article can also be ordered at
httpwwwdekkercomservletproductDOI101081PLN120038544
Request Permission or Order Reprints Instantly
Interested in copying and sharing this article In most cases US Copyright Law requires that you get permission from the articlersquos rightsholder before using copyrighted content
All information and materials found in this article including but not limited to text trademarks patents logos graphics and images (the Materials) are the copyrighted works and other forms of intellectual property of Marcel Dekker Inc or its licensors All rights not expressly granted are reserved
Get permission to lawfully reproduce and distribute the Materials or order reprints quickly and painlessly Simply click on the Request Permission Order Reprints link below and follow the instructions Visit the US Copyright Office for information on Fair Use limitations of US copyright law Please refer to The Association of American Publishersrsquo (AAP) website for guidelines on Fair Use in the Classroom
The Materials are for your personal use only and cannot be reformatted reposted resold or distributed by electronic means or otherwise without permission from Marcel Dekker Inc Marcel Dekker Inc grants you the limited right to display the Materials only on your personal computer or personal wireless device and to copy and download single copies of such Materials provided that any copyright trademark or other notice appearing on such Materials is also retained by displayed copied or downloaded as part of the Materials and is not removed or obscured and provided you do not edit modify alter or enhance the Materials Please refer to our Website User Agreement for more details
ORDER REPRINTS
Table
9
Analysisofvariance
andmeansfortotaldry
matter
yieldN
uptake
Kuptake
Puptake
Cauptake
Mguptake
and
Suptake
forsw
itchgrass
producedunder
variable
ratesandharvestfrequencyPerkinsOK2000
Yield
Nuptake
Kuptake
Puptake
Cauptake
Mguptake
Suptake
Sourceofvariation
df
(meansquares)
Replication
2497183
b16971
193645
b459
a1764
a1595
a127
Cutting
2336977
a198613
b1052774
b6378
b510
8582
b789
b
Ntiming
330364
39508
a109448
a499
a697
a276
203
Nrate
392263
58709
b846
41
1104
a973
a180
a
CuttingaN
rate
825379
47535
b65231
a569
b1527
899
b233
b
NtimingaN
rate
613826
37440
b46573
327
663
629
a160
a
Residualerror
44
47696
9282
19227
140
385
385
51
TotalN
rate
(kgha1)
Cuttiming
(Mgha1)
(kgha1)
01harvest
99
436
662
39
195
70
44
112
1harvest
85
479
697
33
214
65
44
224
1harvest
117
810
1081
56
277
99
79
448
1harvest
99
835
1322
52
270
103
66
896
1harvest
126
977
1296
48
336
124
78
02harvests
91
543
921
111
233
146
61
112
2harvests
96
941
1320
118
271
188
72
224
2harvests
122
1130
1547
142
355
269
94
1220 Thomason et al
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
Request PermissionOrder Reprints
Reprints of this article can also be ordered at
httpwwwdekkercomservletproductDOI101081PLN120038544
Request Permission or Order Reprints Instantly
Interested in copying and sharing this article In most cases US Copyright Law requires that you get permission from the articlersquos rightsholder before using copyrighted content
All information and materials found in this article including but not limited to text trademarks patents logos graphics and images (the Materials) are the copyrighted works and other forms of intellectual property of Marcel Dekker Inc or its licensors All rights not expressly granted are reserved
Get permission to lawfully reproduce and distribute the Materials or order reprints quickly and painlessly Simply click on the Request Permission Order Reprints link below and follow the instructions Visit the US Copyright Office for information on Fair Use limitations of US copyright law Please refer to The Association of American Publishersrsquo (AAP) website for guidelines on Fair Use in the Classroom
The Materials are for your personal use only and cannot be reformatted reposted resold or distributed by electronic means or otherwise without permission from Marcel Dekker Inc Marcel Dekker Inc grants you the limited right to display the Materials only on your personal computer or personal wireless device and to copy and download single copies of such Materials provided that any copyright trademark or other notice appearing on such Materials is also retained by displayed copied or downloaded as part of the Materials and is not removed or obscured and provided you do not edit modify alter or enhance the Materials Please refer to our Website User Agreement for more details
ORDER REPRINTS
448
2harvests
112
1069
1270
126
311
239
81
896
2harvests
132
1398
1709
124
304
272
90
03harvests
137
1391
1928
232
310
234
125
112
3harvests
129
1480
1954
202
342
259
122
224
3harvests
132
1789
1982
202
347
276
133
448
3harvests
125
1948
2073
191
279
241
120
896
3harvests
143
555
518
48
130
111
38
112
2-spN2harv
95
599
973
122
252
158
62
224
2-spN2harv
106
865
867
137
367
218
82
448
2-spN2harv
112
1147
849
128
333
268
91
896
2-spN2harv
115
1186
895
125
321
264
91
112
3-spN3harv
120
1334
1681
207
295
212
109
224
3-spN3harv
128
1759
1967
211
353
251
134
448
3-spN3harv
135
2048
1875
201
342
275
148
896
3-spN3harv
131
1879
1854
188
298
253
126
SED
18
249
358
31
49
49
19
SEDmdash
standard
errorofthedifference
betweentw
oequallyreplicatedmeans
2-spN2harvmdash
2harvestsystem
N
applied
inAprilandafter
firstharvest
3-spN3harvmdash
3harvestsystem
N
applied
inAprilandafter
each
ofthefirsttw
oharvests
abSignificantatthe005and001probabilitylevelrespectively
Switchgrass Response to Applied Nitrogen 1221
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
Request PermissionOrder Reprints
Reprints of this article can also be ordered at
httpwwwdekkercomservletproductDOI101081PLN120038544
Request Permission or Order Reprints Instantly
Interested in copying and sharing this article In most cases US Copyright Law requires that you get permission from the articlersquos rightsholder before using copyrighted content
All information and materials found in this article including but not limited to text trademarks patents logos graphics and images (the Materials) are the copyrighted works and other forms of intellectual property of Marcel Dekker Inc or its licensors All rights not expressly granted are reserved
Get permission to lawfully reproduce and distribute the Materials or order reprints quickly and painlessly Simply click on the Request Permission Order Reprints link below and follow the instructions Visit the US Copyright Office for information on Fair Use limitations of US copyright law Please refer to The Association of American Publishersrsquo (AAP) website for guidelines on Fair Use in the Classroom
The Materials are for your personal use only and cannot be reformatted reposted resold or distributed by electronic means or otherwise without permission from Marcel Dekker Inc Marcel Dekker Inc grants you the limited right to display the Materials only on your personal computer or personal wireless device and to copy and download single copies of such Materials provided that any copyright trademark or other notice appearing on such Materials is also retained by displayed copied or downloaded as part of the Materials and is not removed or obscured and provided you do not edit modify alter or enhance the Materials Please refer to our Website User Agreement for more details
ORDER REPRINTS
Table 10 Surface soil sample (0ndash15 cm) organic C between crowns of plants
and within crowns Chickasha and Perkins OK 2001
Total N
rate
(kg ha1)
HarvestN
timing
Chickasha
(in crown)
Chickasha
(between
crown)
Perkins
(in crown)
Perkins
(between
crown)
(mgC cm1)
0 1 harvest 19138 19731 19726 16712
112 1 harvest 16655 18878 20724 17462
224 1 harvest 20967 23583 19990 15908
448 1 harvest 20714 21431 17752 16524
896 1 harvest 21457 22302 22455 17633
0 2 harvests 17607 21856 20474 13609
112 2 harvests 18285 18997 18439 16741
224 2 harvests 20262 20727 18229 14899
448 2 harvests 17877 20766 16290 13942
896 2 harvests 21788 15722 21675 17539
0 3 harvests 19018 17843 18051 14627
112 3 harvests 19823 17294 20547 16111
224 3 harvests 20844 20076 18089 14954
448 3 harvests 24617 19327 19690 15079
896 3 harvests 18579 18747 18995 15893
112 2 sp N 2 harv 15268 18332 19982 16474
224 2 sp N 2 harv 21517 19420 17189 15261
448 2 sp N 2 harv 20403 21403 18155 14417
896 2 sp N 2 harv 15770 15624 21519 17536
112 3 sp N 3 harv 17095 18335 18021 14397
224 3 sp N 3 harv 20021 18263 19381 16824
448 3 sp N 3 harv 19721 19723 18791 15682
896 3 sp N 3 harv 20779 17655 19163 15157
SED 6623 6693 5462 5531
Mean 19487 19393 19275 15799
Contrasts
1 harvest
N rate linear ns ns ns ns
N rate quad ns ns ns ns
2 harvests
N rate linear ns a ns ns
N rate quad ns ns a ns
3 harvests
N rate linear ns ns ns ns
N rate quad ns a a ns
SEDmdashstandard error of the difference between two equally replicated means
2-sp N 2 harvmdash2 harvest system N applied in April and after first harvest
3-sp N 3 harvmdash3 harvest system N applied in April and after each of the first
two harvestsaSignificant at the 005 probability level
nsmdashnot significant at the 005 porbability level
1222 Thomason et al
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
Request PermissionOrder Reprints
Reprints of this article can also be ordered at
httpwwwdekkercomservletproductDOI101081PLN120038544
Request Permission or Order Reprints Instantly
Interested in copying and sharing this article In most cases US Copyright Law requires that you get permission from the articlersquos rightsholder before using copyrighted content
All information and materials found in this article including but not limited to text trademarks patents logos graphics and images (the Materials) are the copyrighted works and other forms of intellectual property of Marcel Dekker Inc or its licensors All rights not expressly granted are reserved
Get permission to lawfully reproduce and distribute the Materials or order reprints quickly and painlessly Simply click on the Request Permission Order Reprints link below and follow the instructions Visit the US Copyright Office for information on Fair Use limitations of US copyright law Please refer to The Association of American Publishersrsquo (AAP) website for guidelines on Fair Use in the Classroom
The Materials are for your personal use only and cannot be reformatted reposted resold or distributed by electronic means or otherwise without permission from Marcel Dekker Inc Marcel Dekker Inc grants you the limited right to display the Materials only on your personal computer or personal wireless device and to copy and download single copies of such Materials provided that any copyright trademark or other notice appearing on such Materials is also retained by displayed copied or downloaded as part of the Materials and is not removed or obscured and provided you do not edit modify alter or enhance the Materials Please refer to our Website User Agreement for more details
ORDER REPRINTS
switchgrass Similarly overall P Mg and S forage concentrationsincreased with increasing yield (Fig 2)
Average dry biomass yields for one two and three harvests with 0and 448 kgNha1 applied are represented in Figs 3 and 4 for Chickashaand Perkins respectively As was expected yield levels declined with timeat Chickasha (Fig 3) However this same trend was not observed atPerkins (Fig 4) It should be noted that even with changes in dry matteryield nutrient uptake values remained constant This is a concernespecially with increased forage N as increased N uptake will increasebiomass production costs Practical production recommendations fromthis work suggest that N be applied once at the beginning of the growingseason and that N rates remain constant over the life of the stand
Since the goal of this research was to determine maximumrecommended N rates for high production switchgrass data wereaveraged over years and locations to better estimate optimum N ratesand harvest practices The highest annual yield was consistently achievedwith 448 kgNha1 applied all in April and three harvests during theseason averaging 180Mgha1 dry matter production This treatmentalso maximized N K P and S uptake However applying 0N andharvesting three times produced almost as much total biomass
y = 6E-06x + 02701 R2 = 00981
y = 2E-05x + 00491 R2 = 04984
y = 2E-05x - 00983 R2 = 07418
y = 1E-05x - 00186 R2 = 07683
0
005
01
015
02
025
03
035
04
045
05
10000 12000 14000 16000 18000 20000
Yield kg ha-1
Nut
rient
con
cent
ratio
n
P
Ca
Mg
S
y = 6E- 22
- 2
- 2 = 07418
- -
-
P
Figure 2 Ca Mg P and S concentrations with increasing dry biomass yields
Chickasha and Perkins (View this art in color at wwwdekkercom)
Switchgrass Response to Applied Nitrogen 1223
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
Request PermissionOrder Reprints
Reprints of this article can also be ordered at
httpwwwdekkercomservletproductDOI101081PLN120038544
Request Permission or Order Reprints Instantly
Interested in copying and sharing this article In most cases US Copyright Law requires that you get permission from the articlersquos rightsholder before using copyrighted content
All information and materials found in this article including but not limited to text trademarks patents logos graphics and images (the Materials) are the copyrighted works and other forms of intellectual property of Marcel Dekker Inc or its licensors All rights not expressly granted are reserved
Get permission to lawfully reproduce and distribute the Materials or order reprints quickly and painlessly Simply click on the Request Permission Order Reprints link below and follow the instructions Visit the US Copyright Office for information on Fair Use limitations of US copyright law Please refer to The Association of American Publishersrsquo (AAP) website for guidelines on Fair Use in the Classroom
The Materials are for your personal use only and cannot be reformatted reposted resold or distributed by electronic means or otherwise without permission from Marcel Dekker Inc Marcel Dekker Inc grants you the limited right to display the Materials only on your personal computer or personal wireless device and to copy and download single copies of such Materials provided that any copyright trademark or other notice appearing on such Materials is also retained by displayed copied or downloaded as part of the Materials and is not removed or obscured and provided you do not edit modify alter or enhance the Materials Please refer to our Website User Agreement for more details
ORDER REPRINTS
(169Mgha1) This limited response to N is possibly explained by theevolution of switchgrass under low N conditions The highest level of Cauptake was observed in plants receiving 224 kgNha1 split half in Apriland half after first harvest and harvested twice Magnesium uptake washighest where 224 kgNha1 was applied in April and with two harvestsNumber of harvests was most important in determining yields with threeharvests producing 163Mgha1 two harvests producing 147Mgha1
and one harvest averaging 129Mgha1 Multiple harvests maximized
0
5
10
15
20
25
30
35
1998 1999 2000
Year
Yie
ld
Mg
ha-
1
0N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 4 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Perkins OK 1998ndash2000 (View this art in color at
wwwdekkercom)
0
5
10
15
20
25
30
35
1997 1998 1999 2000Year
Yie
ld
Mg
ha-
10N 1harv0N 2harv0N 3harv448N 1harv448N 2harv448N 3harv
Figure 3 Average yearly dry matter yields over time as influenced by N rate and
harvest frequency Chickasha OK 1997ndash2000 (View this art in color at
wwwdekkercom)
1224 Thomason et al
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
Request PermissionOrder Reprints
Reprints of this article can also be ordered at
httpwwwdekkercomservletproductDOI101081PLN120038544
Request Permission or Order Reprints Instantly
Interested in copying and sharing this article In most cases US Copyright Law requires that you get permission from the articlersquos rightsholder before using copyrighted content
All information and materials found in this article including but not limited to text trademarks patents logos graphics and images (the Materials) are the copyrighted works and other forms of intellectual property of Marcel Dekker Inc or its licensors All rights not expressly granted are reserved
Get permission to lawfully reproduce and distribute the Materials or order reprints quickly and painlessly Simply click on the Request Permission Order Reprints link below and follow the instructions Visit the US Copyright Office for information on Fair Use limitations of US copyright law Please refer to The Association of American Publishersrsquo (AAP) website for guidelines on Fair Use in the Classroom
The Materials are for your personal use only and cannot be reformatted reposted resold or distributed by electronic means or otherwise without permission from Marcel Dekker Inc Marcel Dekker Inc grants you the limited right to display the Materials only on your personal computer or personal wireless device and to copy and download single copies of such Materials provided that any copyright trademark or other notice appearing on such Materials is also retained by displayed copied or downloaded as part of the Materials and is not removed or obscured and provided you do not edit modify alter or enhance the Materials Please refer to our Website User Agreement for more details
ORDER REPRINTS
yields in every year when compared to one harvest While multiple
harvests have produced more forage in the early years of this study visual
observations indicate a decline in switchgrass stands after 3ndash4 years of
intensive harvest management Even though there were fewer plants in a
given area where multiple harvests were employed those treatmentsproduced more dry matter than those with higher plant density but this
may change as the stand ages If density continues to decline then at
some point biomass yield will necessarily decline It appears that
management to maximize productivity in the short-term may shorten
the life span of a switchgrass stand
REFERENCES
1 McLaughlin SB Samson R Bransby D Wiseloge A Evaluating
physical chemical and energetic properties of perennial grasses as
biofuels In Proceedings of the Seventh National Bioenergy
Conference Partnerships to Develop and Apply Biomass
Technologies Nashville TN Sept 15ndash20 19962 Fox G Girouard P Syukat Y An economic analysis of the
financial viability of switchgrass as a raw material for pulp produc-
tion in eastern Ontario Biomass and Bioenergy 1999 16 1ndash123 Balasko JA Smith D Influence of temperature and nitrogen
fertilization on the growth and composition of switchgrass and
timothy at anthesis Agron J 1971 63 853ndash8574 Madakadze JC Stewart K Peterson PR Coulman BE Smith
DL Cutting frequency and nitrogen fertilization effects on yield and
nitrogen concentration of switchgrass in a short season area Crop
Sci 1999 39 552ndash5605 Staley TE Stout WL Jung GA Nitrogen use by tall fescue and
switchgrass on acidic soils of varying water holding capacity Agron
J 1991 83 732ndash7386 Stout WL Jung GA Biomass and nitrogen accumulation in
switchgrass effects of soil and environment Agron J 1995 87
663ndash6697 Stout WL Jung GA Shaffer JA Effects of soil and nitrogen on
water use efficiency of tall fescue and switchgrass under humid
conditions Soil Sci Soc Am J 1998 52 429ndash4348 Stout WL Staley TE Shaffer JA Jung GA Quantitative
effects of soil depth and soil and fertilizer nitrogen on nitrogen
uptake by tall fescue and switchgrass Commun Soil Sci Plant Anal
1991 22 1647ndash1660
Switchgrass Response to Applied Nitrogen 1225
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
Request PermissionOrder Reprints
Reprints of this article can also be ordered at
httpwwwdekkercomservletproductDOI101081PLN120038544
Request Permission or Order Reprints Instantly
Interested in copying and sharing this article In most cases US Copyright Law requires that you get permission from the articlersquos rightsholder before using copyrighted content
All information and materials found in this article including but not limited to text trademarks patents logos graphics and images (the Materials) are the copyrighted works and other forms of intellectual property of Marcel Dekker Inc or its licensors All rights not expressly granted are reserved
Get permission to lawfully reproduce and distribute the Materials or order reprints quickly and painlessly Simply click on the Request Permission Order Reprints link below and follow the instructions Visit the US Copyright Office for information on Fair Use limitations of US copyright law Please refer to The Association of American Publishersrsquo (AAP) website for guidelines on Fair Use in the Classroom
The Materials are for your personal use only and cannot be reformatted reposted resold or distributed by electronic means or otherwise without permission from Marcel Dekker Inc Marcel Dekker Inc grants you the limited right to display the Materials only on your personal computer or personal wireless device and to copy and download single copies of such Materials provided that any copyright trademark or other notice appearing on such Materials is also retained by displayed copied or downloaded as part of the Materials and is not removed or obscured and provided you do not edit modify alter or enhance the Materials Please refer to our Website User Agreement for more details
ORDER REPRINTS
9 Balasko JA Burner DM Thayne WV Yield and quality ofswitchgrass grown without soil amendments Agron J 1984 76204ndash208
10 Sanderson MA Read JC Reed RL Harvest management ofswitchgrass for biomass feedstock and forage production Agron J1999 91 5ndash10
11 Sanderson MA Morphological development of switchgrass andkleingrass Agron J 1992 84 415ndash419
12 Madakadze JC Stewart K Peterson PR Coulman BESmith DL Switchgrass biomass and chemical composition forbiofuel in eastern Canada 1999b Agron J 1999 91 696ndash701
13 Hall KE George JR Riedl RR Herbage dry matter yields ofswitchgrass big bluestem and indiangrass with N fertilizationAgron J 1982 74 47ndash51
14 Bransby DI McLaughlin SB Parrish DJ A review of carbonand nitrogen balances in switchgrass grown for energy Biomass andBioenergy 1998 14 379ndash384
15 Ma Z Wood CW Bransby DI Soil management impacts onsoil carbon sequestration by switchgrass Biomass and Bioenergy2000 18 469ndash477
16 Schepers JS Francis DD Thompson MT Simultaneousdetermination of total C total N and 15N on soil and plantmaterial Commun Soil Sci Plant Anal 1989 20 949ndash959
17 Mehlich A Mehlich number 3 extractant a modification ofMehlich number 2 extractant Commun Soil Sci Plant Anal1984 15 1409ndash1416
18 Benton JB Jr Case VW Sampling handling and analyzingplant tissue samples In Soil Testing and Plant Analysis 3rd EdWesterman RL Ed SSSA Madison WI 1990 SSSA BookSer 3 389ndash427
19 SAS Institute SASSTAT Userrsquos Guide Version 6 4th Ed SASInstitute Cary NC 1989 Vol 2
20 Cullison AE Feeds and Feeding Reston Publishing Co RestonVA 1975
21 Raun WR Solie JB Johnson GV Stone ML WhitneyRW Lees HL Sembiring H Phillips SB Micro-variability insoil test plant nutrient and yield parameters in bermudagrass SoilSci Soc Am J 1998 62 683ndash690
22 Garten GT Wullschleger SD Soil carbon dynamics beneathswitchgrass as indicated by stable isotope analysis J Environ Qual2000 29 645ndash653
1226 Thomason et al
Request PermissionOrder Reprints
Reprints of this article can also be ordered at
httpwwwdekkercomservletproductDOI101081PLN120038544
Request Permission or Order Reprints Instantly
Interested in copying and sharing this article In most cases US Copyright Law requires that you get permission from the articlersquos rightsholder before using copyrighted content
All information and materials found in this article including but not limited to text trademarks patents logos graphics and images (the Materials) are the copyrighted works and other forms of intellectual property of Marcel Dekker Inc or its licensors All rights not expressly granted are reserved
Get permission to lawfully reproduce and distribute the Materials or order reprints quickly and painlessly Simply click on the Request Permission Order Reprints link below and follow the instructions Visit the US Copyright Office for information on Fair Use limitations of US copyright law Please refer to The Association of American Publishersrsquo (AAP) website for guidelines on Fair Use in the Classroom
The Materials are for your personal use only and cannot be reformatted reposted resold or distributed by electronic means or otherwise without permission from Marcel Dekker Inc Marcel Dekker Inc grants you the limited right to display the Materials only on your personal computer or personal wireless device and to copy and download single copies of such Materials provided that any copyright trademark or other notice appearing on such Materials is also retained by displayed copied or downloaded as part of the Materials and is not removed or obscured and provided you do not edit modify alter or enhance the Materials Please refer to our Website User Agreement for more details
Request PermissionOrder Reprints
Reprints of this article can also be ordered at
httpwwwdekkercomservletproductDOI101081PLN120038544
Request Permission or Order Reprints Instantly
Interested in copying and sharing this article In most cases US Copyright Law requires that you get permission from the articlersquos rightsholder before using copyrighted content
All information and materials found in this article including but not limited to text trademarks patents logos graphics and images (the Materials) are the copyrighted works and other forms of intellectual property of Marcel Dekker Inc or its licensors All rights not expressly granted are reserved
Get permission to lawfully reproduce and distribute the Materials or order reprints quickly and painlessly Simply click on the Request Permission Order Reprints link below and follow the instructions Visit the US Copyright Office for information on Fair Use limitations of US copyright law Please refer to The Association of American Publishersrsquo (AAP) website for guidelines on Fair Use in the Classroom
The Materials are for your personal use only and cannot be reformatted reposted resold or distributed by electronic means or otherwise without permission from Marcel Dekker Inc Marcel Dekker Inc grants you the limited right to display the Materials only on your personal computer or personal wireless device and to copy and download single copies of such Materials provided that any copyright trademark or other notice appearing on such Materials is also retained by displayed copied or downloaded as part of the Materials and is not removed or obscured and provided you do not edit modify alter or enhance the Materials Please refer to our Website User Agreement for more details