Nutrient Runoff from Pasture after Incorporation of Poultry Litteror Inorganic Fertilizer

D. J. Nichols,* T. C. Daniel, and D. R. Edwards

ABSTRACTLand-applied poultry litter can elevate N, P, and C concentrations

in surface water runoff. This study tested the hypothesis that incorpora-tion of surface-applied poultry litter and inorganic fertilizer by rotarytillage would improve runoff quality from tall fescue (Festuca arundina-cea Schreber) pasture. Captina silt loam (fine-silty, siliceous, mesicTypic Fragiudult) plots with 5% slopes and fescue cover received 4.5Mg litter ha"1 or fertilizer equivalent to 218 kg N ha"1 and 87 kg Pha"1. Litter and fertilizer were surface applied or incorporated 2 to3 cm deep by rotary tillage. Simulated rainfall was applied 7 d laterat 50 mm h~' to produce continuous runoff for 0.5 h. Runoff concentra-tions and mass losses of measured constituents were not significantlydifferent (a = 0.05) between surface-applied and incorporated treat-ments. Runoff concentrations of total Kjeldahl N (TKN), NHi-N,NO3-N, total P (TP), PO4-P, chemical oxygen demand (COD), andtotal suspended solids (TSS) averaged 32.5, 12.4, 1.1, 15.4, 10.4,427.8, and 86.8 mg L~' for litter treatments, and 37.5, 39.0, 2.6,26.2, 26.1, 87.8, and 20.6 mg L'1 for fertilizer treatments. Masslosses of TKN, NH3-N, NO3-N, TP, PO4-P, COD, and TSS averaged2.8, 1.0, 0.1, 1.3, 0.9, 32.3, and 6.7 kg ha-' for litter and 2.9, 3.4,0.2, 2.0, 2.0, 12.7, and 2.1 kg ha ~' for fertilizer treatments. Runoffmass losses of TKN and TP were not significantly different betweenUtter and fertilizer treatments. Averaged across all treatments andreplications, mass losses of TKN and TP were 2.8 and 1.7 kg ha~',representing 1.3% of applied N and 1.9% of applied P.

CONCENTRATED POULTRY PRODUCTION creates largequantities of manure. For example, confined poultry

generated =13.1 million Mg of manure and litter (dry-weight basis) in 1990, 68% of which was produced bybroilers (Moore et al., 1994). Litter is a combination ofmanure and bedding materials such as pine shavings orrice hulls. In Arkansas, the leading broiler-producingstate, broilers alone generated approximately 1.4 millionMg of litter (U.S. Department of Agriculture, 1991).Most of Arkansas' poultry production occurs in the north-west corner of the state (Arkansas Agricultural StatisticsService, 1992), and the litter in this region is usuallysurface applied to nearby pastures without incorporation.

Land application of poultry litter has been shown tosignificantly increase yields of pasture grasses such astall fescue, bermudagrass [Cynodon dactylon (L.) Pers.var. dactylon} and tall fescue-clover (Trifolium spp.) byas much as 306, 215, and 51%, respectively, followinglitter applications of 13 Mg ha"1 (Huneycutt et al., 1988).Hileman (1973) also observed yield increases as high as172% for orchardgrass (Dactylis golmerata L.) followingapplication of 13 Mg ha"1 poultry litter. Disposal of thelitter is sometimes the primary reason for application to

D.J. Nichols and T.C. Daniel, Dep. of Agronomy, 115 Plant ScienceBuilding, and D.R. Edwards, Biological and Agricultural EngineeringDep., 203 Engineering Hall, Univ. of Arkansas, Fayetteville, AR 72701.Received 28 Apr. 1993. *Corresponding author (tdaniel@uafsysb.u-ark.edu).

Published in Soil Sci. Soc. Am. J. 58:1224-1228 (1994).

pastures, with crop fertilization considerations of second-ary importance.

Land application of poultry wastes can cause changesin runoff quality. In a laboratory study, Westerman etal. (1983) amended bare Norfolk sandy loam (fine-loamy,siliceous, thermic Typic Kandiudult) and Cecil clay(clayey, kaolinitic, thermic Typic Kanhapludult) withpoultry litter and manure (no bedding material) at twoapplication rates (214 and 428 kg N ha"1) and applied50 and 100 mm h"1 of simulated rainfall 1 and 3 d afterlitter and manure application. Runoff concentrations andmass losses (nutrients removed in runoff) of litter andmanure components increased with application rate.Mass losses of litter and manure components also in-creased with increasing rainfall intensity.

McLeod and Hegg (1984) examined the effect of poul-try manure applications to fescue pasture on quality ofrunoff using simulated rainfall events applied at weeklyintervals. By the second runoff event, runoff concentra-tions of TKN were reduced by 79%, TP by 56%, andCOD by 57% relative to the first runoff event. Totalnutrient losses after four events were <4% of appliedTKN and COD and <2.5% of TP. Nutrient concentra-tions in runoff were not significantly different betweenmanure-treated and control plots after the 7-d rainfallevent.

A field study conducted by Edwards and Daniel (1993)examined the effects of application rate and rainfall inten-sity on runoff from fescue pastures amended with broilerlitter. Poultry litter was applied at 0, 218, 435, and 870kg N ha"1. Simulated rainfall was applied 1 d after litterapplication at 50 and 100 mm h"1. Increasing applicationrates proportionately increased runoff concentrations ofall litter constituents investigated. Mass losses of litterconstituents increased significantly with both litter appli-cation rate and rainfall intensity. At the high rainfallintensity, as much as 18.7% of total applied N and 7.3%of total applied P were lost in runoff. These data indicatethe possible magnitude of litter constituent losses inrunoff when relatively severe rainfall events occur soonafter litter application.

From a water quality standpoint, the N and P inrunoff are especially problematic. Concentrations of 0.3mg inorganic N and 0.01 mg inorganic P L"1 or higherhave been proposed as levels above which excessivealgal growth or eutrophication can occur (Sawyer, 1947;Vollenweider, 1968). Because litter application rates aregenerally based on crop N requirements (Huneycutt etal., 1988), P is typically applied at rates in excess ofcrop needs and may enter surface waters in runoff.Phosphorus is most often the nutrient limiting eutrophica-

Abbreviations: TN, total N; TKN, total Kjeldahl N; TP, total P; COD,chemical oxygen demand; TSS, total suspended solids; EC, electricalconductivity.

1224

NICHOLS ET AL.: NUTRIENT RUNOFF FROM POULTRY LITTER OR INORGANIC FERTILIZER 1225

tion of inland waters (Levine and Schindler, 1989). Eu-trophic waters can adversely affect fish and other aquaticlife, increase treatment costs, and reduce aesthetic ap-peal. Consequently, best management practices (BMPs)need to be developed and implemented to minimize land-applied poultry litter contributions to runoff.

Incorporation of fertilizers and other soil amendmentsis commonly practiced to aid nutrient retention and subse-quent plant uptake. Several studies have examined theimpact of incorporation of soil amendments on runoffquality. Timmons et al. (1973) found that incorporationof fertilizer in Barnes loam (fine-loamy, mixed UdicHaploboroll) by plowing followed by disking resultedin N and P losses about equal to those in surface runofffrom unfertilized plots. They also found, however, thatdisking-in fertilizer that had been broadcast on fallowplots did not significantly reduce N and P losses in runoff.Ross et al. (1979) injected liquid dairy manure 15.3 and30.5 cm into bare Maury silt loam (fine, mixed, mesicTypic Paleudalf) and bluegrass (Poa sp.) sod. Injectionessentially eliminated manure N and P losses in runoffcompared with surface application. Baker and Laflen(1982) injected fertilizer 5 cm into fallow Clarion sandyloam (fine-loamy, mixed, mesic Typic Hapludoll) andfound that NHt-N and dissolved P concentrations inrunoff from treated plots were not significantly differentfrom those observed for control plots. Similar resultswere reported by Mueller et al. (1984), who observedthat chisel plowing of surface-applied dairy manure inDresden silt loam (fine-loamy over sandy or sandy-skeletal, mixed, mesic Mollic Hapludalf) reduced TPlosses primarily by reducing runoff. Giddens and Barnett(1980) incorporated 11.2 and 22.4 Mg ha"1 of poultrylitter 10 cm into fallow Cecil sandy loam and evaluatedtotal coliforms in runoff. This study indicated that incor-porating litter generally reduced coliforms during thelatter stages of runoff.

To date, information on the efficacy of incorporatingpoultry litter on pastures in improving runoff water qual-ity is lacking. In addition, studies have not been con-ducted to determine the runoff water quality changescaused by incorporation of inorganic fertilizer on pas-tures. The objective of this study was to evaluate thehypothesis that incorporation of surface-applied poultrylitter and inorganic fertilizer would improve runoff qual-ity from fescue pasture.

MATERIALS AND METHODSRunoff plots with uniform slopes of 5% were established

on a Captina silt loam. Each plot was 1.5 m wide (across theslope) by 6 m long (down the slope). The plots were establishedin tall fescue in the fall of 1990. Each plot was surroundedby a metal border to isolate runoff. A self-cleaning runoffcollector as described by Edwards and Daniel (1993) wasplaced at the downslope edge of the plot.

The experimental design was factorial with three replica-tions. The variables were amendment (poultry litter or inor-ganic fertilizer) and application method (surface applicationor incorporation by rotary tillage).

The poultry litter consisted of broiler manure and a sawdust-

rice hulls bedding material. The litter was collected in plasticbags, and subsamples were analyzed by the University ofArkansas Agricultural Services Laboratory. The litter wasrefrigerated at 4°C for 1 wk prior to application to the plotsto minimize nutrient transformations in the litter.

The poultry litter water content was determined by weighingbefore and after drying at 105 °C for 24 h. Total N wasdetermined by the combustion method (Campbell, 1992). Inor-ganic N composition was determined by distillation after extrac-tion with 2 M KC1. Phosphorus content was analyzed byinductively coupled plasma spectrophotometry (Donohue andAho, 1992) after preparation according to Campbell and Plank(1992). Electrical conductivity and pH were determined on1:1 and 2:1 water/litter mixtures, respectively. The litter char-acteristics and constituent application rates are indicated inTable 1.

The inorganic fertilizer treatment consisted of commerciallyavailable 13-5.7-10.8 (N-P-K) and NHtNC^ fertilizers. Inor-ganic fertilizer was applied at 218 kg N ha~' and 87 kg Pha"1 to match the N and P amounts applied to the litter-treatedplots.

Litter and inorganic fertilizer were uniformly applied tothe respective plot surfaces. Incorporation treatments wereimmediately tilled across the slope using a gasoline-poweredrotary tiller with tines on approximately 150-mm centers. Eachtine was 1 mm wide and cut approximately 10 mm laterally.Litter and fertilizer were incorporated into the top 2 to 3 cmof soil to minimize damage to the fescue roots.

Seven days after litter and fertilizer were either surfaceapplied or incorporated, simulated rainfall was applied to allplots at a rate of 50 mm h~'. The rainfall simulators usedwere described by Edwards et al. (1992). All plots receivedsufficient simulated rainfall to produce 0.5 h of continuousrunoff.

Runoff samples of approximately 1 L were collected inpolyethylene containers at 0.08-h intervals starting 0.04 h afterthe beginning of uninterrupted runoff. Sample volumes andcollection times were recorded. These data were used to de-velop hydrographs, calculate runoff volumes, and constructflow-weighted composite samples from six corresponding dis-crete samples.

Runoff samples were analyzed using standard methods(Greenberg et al., 1992). Following runoff collection, aliquotsof discrete and composite samples were filtered through 0.45-(im filters for ortho-P (PO4-P) analysis. Unfiltered sampleswere refrigerated at 4°C until analyzed. The macro-Kjeldahlmethod was used for TKN analysis. Ammonia-N was deter-mined by the ammonia-selective electrode method. An ionchromatograph (Dionex DX-300 Gradient ChromatographySystem, Dionex Corp., Sunnyvale, CA) was used in analysisof NO3-N and PO4-P. Total P was determined by the ascorbicacid colorimetric method following rkSCX-HNOa digestion.The COD was measured using the closed reflux, colorimetricmethod.Table 1. Concentrations and rates of poultry litter constituents

applied to fescue pasture.

Constituent

H2OTotal NNH3-NNOj-NTotal PPHElectrical conductivity, S m"1

Concentration

nig kg'1

IWOOOt387333512

25615667

7.810

Application rate

kg ha-'

217.619.71.4

87.4

t Mean of three samples.

1226 SOIL SCI. SOC. AM. J., VOL. 58, JULY-AUGUST 1994

Table 2. Concentrations of incorporated or surface-applied poultry litter and inorganic fertilizer constituents in runoff from fescue pasture.Litter Fertilizer

Constituent

TKNNH3-NNO3-NTPPO4-PCODTSSEC, S m-'

Incorporated

34.2$12.41.0

14.19.2

360.481.8

O.OS

Surface applied

30.812.41.2

16.711.5

495.191.70.06

Incorporated———— mg L-> —————

36.036.62.9

24.424.988.327.70.06

Surface applied

38.941.32.2

27.927.387.313.50.06

LSD (0.05)

NS8.30.76.95.1

195.920.2NS

t TKN = Total Kjeldahl N, TP = total P, COD = chemical oxygen demand, TSS = total suspended solids, EC = electrical conductivity.t Mean of three samples.

RESULTS AND DISCUSSIONRunoff

Simulated rainfall required to produce runoff was notsignificantly (a = 0.05) different between surface-applied and incorporated treatments or between poultrylitter and inorganic fertilizer. Averaged across all treat-ments and replications, the mean simulated rainfall ap-plied prior to initiation of continuous runoff was 16.5mm. A natural storm of greater intensity than the simu-lated rain event described above occurs approximatelyonce every year in Arkansas (Hershfield, 1961).

There were no significant differences (a = 0.05) inrunoff volumes due to incorporation of litter or fertilizer.The mean runoff volume averaged across all treatmentsand replications was 7.9 mm.

Nutrient Concentrations in RunoffMean concentrations of runoff constituents within

treatments are given in Table 2. Runoff concentrationsfrom undisturbed surface-applied poultry litter or inor-ganic fertilizer treatments did not differ significantly(a = 0.05) from incorporated litter or fertilizer meanrunoff concentrations. The cultivation practice employed(rotary tillage) apparently did not adequately turn underme surface-applied litter and fertilizer to significantlydecrease their contributions to runoff compared withundisturbed fescue plots.

There were no significant differences (a = 0.05) inTKN concentrations in runoff between litter and fertilizertreatments. Species distributions of N in runoff differedsignificantly (a = 0.05) between litter and fertilizertreatments. About 62% of TKN hi runoff from poultry

litter treatments was organic N, reflecting the large or-ganic-N content of the poultry litter. Virtually all N inrunoff from inorganic fertilizer treatments was in theinorganic form. Nitrate-N concentrations were signifi-cantly higher (a = 0.05) from inorganic fertilizer treat-ments than from poultry litter treatments and constitutedapproximately 7 and 3% of runoff N, respectively.

Total P concentrations in runoff were significantlylower (a = 0.05) from plots amended with poultry litter,although equivalent TP rates were applied hi litter andfertilizer. These differences may have resulted fromdiffering susceptibilities to runoff transport between thetwo P sources. The concentrations of P forms alsodiffered significantly (a = 0.05) between litter and fertil-izer treatments. Ortho-P constituted approximately 67%of total P in runoff from poultry litter treatments, whereasessentially all P in runoff from the inorganic fertilizertreatments was PO4-P.

Chemical oxygen demand and TSS concentrationswere significantly higher (a = 0.05) in runoff frompoultry-litter treatments. The differences hi COD andTSS concentrations are attributed to different propertiesof the litter and fertilizer; i.e., the litter contained signifi-cant organic matter and fine particles.

No significant differences (a = 0.05) hi EC wereobserved between the litter and fertilizer treatments.

Nutrient Mass Losses in RunoffMean mass losses of runoff constituents within treat-

ments are given in Table 3. Incorporation had no signifi-cant (a = 0.05) effect on mass losses of any litter orfertilizer constituents in runoff compared with undis-turbed surface-applied treatments. Mass losses of N and

Table 3. Mass losses of incorporated or surface-applied poultry litter and inorganic fertilizer constituents in runoff from fescue pasture.

Litter Fertilizer

Constituent! Incorporated Surface applied Incorporated Surface applied LSD (0.05)

TKNNH3-NNO3-NTPP04-PCODTSS

3.4t1.20.11.40.9

34.17.4

2.10.80.11.10.8

30.45.9

———— kg ha-' ——————3.63.70.32.52.68.92.2

2.02.10.21.91.85.80.9

NSNS0.1NSNS16.41.9

t TKN = Total Kjeldahl N, TP = total P, COD = chemical oxygen demand, TSS = total suspended solids.$ Mean of three samples.

NICHOLS ET AL.: NUTRIENT RUNOFF FROM POULTRY LITTER OR INORGANIC FERTILIZER 1227

14

o-C

oC3

OL

12 -

10 -

10 15 20 25 30

Time after beginning of runoff (min)Fig. 1. Total Kjeldahl nitrogen (TKN) and total phosphorus (TP)

mass losses from fescue pasture at 5-min intervals during a runoffevent.

P forms in runoff were also unaffected (a = 0.05) byincorporation.

No significant mass loss differences (a = 0.05) ofTKN, NH3-N, TP, or PO4-P were evident between litterand fertilizer treatments. Although runoff concentrationsof NH3-N, TP and PO4-P were significantly differentbetween litter and fertilizer treatments, load differenceswere probably nonsignificant due to variability in runoffvolumes. Averaged across all treatments and replica-tions, the mean average mass losses of TKN, NH3-N,TP and PO4-P in runoff were 2.8, 2.2, 1.7, and 1.5kg ha"1, respectively. These losses represent 1.3% ofapplied total N and 1.9% of applied total P.

Significantly greater N as NO3-N was lost from thefertilizer than from poultry litter treatments, thoughNO3-N losses from fertilizer and litter accounted foronly 0.1 and 0.05% of total applied N, respectively.Chemical oxygen demand and TSS loads were signifi-cantly higher (a = 0.05) from the litter-treated plots,reflecting differences in litter and fertilizer compositionas described above.

Since runoff mass losses of TKN and TP were notsignificantly different between litter or fertilizer treat-ments or between surface-applied and incorporated treat-ments, the data from discrete samples have been com-bined to illustrate changes hi runoff mass losses withina runoff event (Fig. 1). Peak nutrient mass losses werecarried in the runoff approximately 15 min after initiationof continuous runoff. Thereafter, TKN and TP masslosses decreased or leveled off due to their depletionfrom the soil-runoff interface.

CONCLUSIONSThe data gathered in this study indicate that shallow

(2-3 cm) incorporation of poultry litter or inorganic

fertilizer by rotary tillage has no significant effect onrunoff quality for a storm occurring 7 d after application.The inherent nutrient retention and infiltration capabili-ties of undisturbed fescue pasture may have been im-paired by the rotary tillage. Visual inspection of thetilled plots indicated that the fescue thatch covering thesoil surface was disrupted by the tillage. The ability ofthe thatch to retain applied litter and fertilizer nutrientsmay have been impaired or diminished as a result.

In addition, tillage brought soil and thatch materialshigher in the fescue crop profile and may have increasedthe susceptibility of these nutrients to removal by runoff.As a result, improvements in nutrient retention by tillagemay have been offset by damage to the grass and thatchsoil covering.

A tillage practice that more thoroughly turns underthe litter or fertilizer might reduce nutrients hi runoffmore effectively than the practice evaluated in this study.However, more aggressive tillage could be injuriousto pasture grasses, expensive to implement, and couldincrease soil erosion.

With or without incorporation, runoff losses of appliedN and P were not > 1.3 and 1.9%, respectively. Theserelatively small nutrient losses indicate that the contribu-tions of pasture-applied litter and fertilizer in runoff maybe of interest primarily from their possible impacts onwater quality, since the losses were minimal from a cropproduction standpoint.

1228 SOIL SCI. SOC. AM. J., VOL. 58, JULY-AUGUST 1994