Tillage, cover cropping, and poultry litter effects onselected soil chemical properties

E.Z. Nyakatawaa, K.C. Reddya,*, K.R. Sistanib

aDepartment of Plant and Soil Science, Alabama A&M University, PO Box 1208, Normal, AL 35762, USAbUSDA/ARS, Waste Management and Forage Research Unit, PO Box 5367, 810 Hwy 12 East, Mississippi State, MS 39762, USA

Received 9 June 2000; received in revised form 3 October 2000; accepted 12 October 2000

Abstract

Conservation tillage systems such as no-till with winter rye cover cropping change soil chemical properties, which affect

crop growth and the environment. The objectives of this study were to investigate the effect of no-till and mulch-till systems,

surface application of poultry litter, and winter rye (Secale cereale L.) cover crop on soil pH, soil organic matter (SOM), and

N and P concentrations in cotton (Gossypium hirsutum L.) plots. The study was done on a Decatur silt loam in north Alabama

from 1996 to 1998. SOM under no-till and mulch-till systems in the 0±15 cm soil depth in November 1998 was 22 g kgÿ1

�P < 0:05� compared with 15 g kgÿ1 in November 1996. A similar result was obtained with winter rye cover cropping

compared with cotton±winter fallow system. Surface application of poultry litter at 100 or 200 kg N haÿ1 increased SOM by

55±80%. In the 200 kg N haÿ1 poultry litter treatment, NH4 in the 30±90 cm soil depth in November 1998 was 22% higher

than that in November 1996. Compared with the ammonium nitrate, the poultry litter treatment plots had up to 40% more NO3

in the 0±30 cm soil depth after the ®rst year of study. Extractable P and soil pH at the end of the study were similar to those at

the beginning. This study shows that no-till and mulch-till, winter rye cover cropping, and surface application of poultry litter

in cotton production systems can rapidly increase surface SOM. The increase in SOM was attributed to less biological

oxidation of crop residues and from soil C contributed by poultry litter. Crop uptake of N and P prevented a signi®cant build

up of these nutrients. These results are important to production systems in the US cotton belt where soil productivity is

threatened by erosion because of low SOM levels and the safe disposal of poultry litter is becoming a major environmental

problem. # 2001 Elsevier Science B.V. All rights reserved.

Keywords: Cotton; Cover crop; Mulch-till; No-till; Poultry litter; RUSLE, soil erosion; Soil organic matter

1. Introduction

Implementation of conservation tillage systems

such as no-till and mulch-till for soil erosion control

in cotton production systems may lead to signi®cant

changes in soil physical, chemical, and biological

properties in the plow layer, in addition to changes

in cotton growth and yield. These changes can have a

signi®cant impact on the environment and hence the

sustainability of cotton production systems.

Soil organic matter (SOM) stabilizes soil pH, which

plays a central role in nutrient supply and availability

for plant uptake (Campbell et al., 1996). Other soil

factors that are positively in¯uenced by SOM include

cation exchange capacity, water holding capacity,

microbial activity, soil tilth, soil structure, water

Soil & Tillage Research 58 (2001) 69±79

* Corresponding author. Tel.: �1-256-858-4191;

fax: �1-256-851-5429.

E-mail address: reddyc@aamu.edu (K.C. Reddy).

0167-1987/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved.

PII: S 0 1 6 7 - 1 9 8 7 ( 0 0 ) 0 0 1 8 3 - 5

and air in®ltration, and soil temperature. In addition,

SOM reduces soil compaction and crusting and

cements soil particles together which reduces erosion.

Sequestration of C from atmospheric CO2 into SOM

has been identi®ed as a signi®cant way to mitigate

global warming.

Levels of SOM depend largely on the type of tillage

and residue management practices which the soil is

subjected to. Many studies have documented the

progressive decline of SOM in cultivated soils due

to conventional tillage systems (Unger, 1991; Chris-

tensen et al., 1994; Alvarez et al., 1995; Burgess et al.,

1996). The amount of C input into the soil from crop

residues increases SOM (Peterson et al., 1998; Hen-

drix et al., 1998). N fertilization increases residue

production, which improves C and N in the soil

(Rasmussen et al., 1998).

Improper use of poultry litter in crop production is

detrimental to the environment. According to Bitzer

and Sims (1988), excessive application of poultry

litter in some cropping systems has resulted in NO3

contamination of groundwater. Problems caused by

high NO3 concentrations in drinking water include

methaemoglobinaemia (blue baby syndrome), cancer,

and respiratory illness in humans and fetal abortions in

livestock (Stevenson, 1986). High concentrations of P

in surface waters, largely resulting from surface runoff

of sediment P causes eutrophication (Schindler, 1977;

Sharpley et al., 1996). Eutrophication has been sug-

gested as the main cause of impaired surface water

resources (US Environmental Protection Agency,

1996). Kingery et al. (1994) found signi®cant accu-

mulation of NO3 and extractable P near the soil bed-

rock when poultry litter was used for fertilizing

pasture land in north Alabama. In corn (Zea mays

L.), poultry litter causes signi®cant leaching of NO3 to

ground water (Liebhardt et al., 1979).

Research on the effect of conservation tillage sys-

tems on soil chemical properties has been extensively

done in the humid and sub-humid regions where wheat

(Triticum aestivum L.) and corn are the dominant

crops (Dick, 1983; Lamb et al., 1985; Wood et al.,

1991; Christensen et al., 1994; Campbell et al., 1996;

Alvarez et al., 1998). Such studies with cotton are

scarce and the results obtained from the cereal-based

cropping systems may be different from those for

cotton for three reasons. First, cotton is grown in

wider row spacings of up to 1 m and produces

less crop residues compared with corn and wheat.

Second, the deep tap root system of cotton may

in¯uence nutrient movement in the soil depth differ-

ently from that of the shallow cereal ®brous root

systems. Third, cotton is grown in warmer and drier

regions and has a long season compared with that of

corn and wheat.

The objectives of this study were to investigate the

effect of no-till and mulch-till systems, application of

poultry litter and winter rye cover crop on soil pH,

organic matter, N and P in cotton plots in north

Alabama.

2. Materials and methods

2.1. Study location and treatments

The study was conducted at the Alabama Agricul-

tural Experiment Station, Belle Mina, AL (348410N,

868520W) on a Decatur silt loam (clayey, kaolinitic

thermic, Typic Paleudults) from 1996 to 1998. The

treatments included three tillage systems: conven-

tional till, mulch-till and no-till; two cropping sys-

tems: cotton±winter fallow (cotton in summer and

fallow in winter), and cotton±rye sequential cropping

(cotton in summer and rye in winter); three N rates: 0,

100 and 200 kg N haÿ1 and two N sources: ammo-

nium nitrate and fresh poultry litter. Ammonium

nitrate was used at one rate of 100 kg N haÿ1 only.

In addition, a continuous bare fallow treatment was

included. The experimental design was a randomized

complete block design with four replications. Plots

were 8 m wide and 9 m long, which resulted in eight

rows of cotton, 1 m apart. Treatments were repeated

on the same plots in 1997 and 1998. Mean monthly

temperature, total monthly rainfall, and cumulative

irrigation water applied to cotton plots at Belle Mina

in 1997 and 1998 were recorded (Table 1).

Conventional tillage included moldboard plowing

in November and disking in April before cotton

seeding. A ®eld cultivator was used to prepare a

smooth seedbed after disking. A ®eld cultivator and

spot applications of herbicides were used for control-

ling weeds during the season. Mulch-till included

tillage with a ®eld cultivator to partially incorporate

crop residues before cotton seeding. No-till involved

seeding without any tillage operation. The crop

70 E.Z. Nyakatawa et al. / Soil & Tillage Research 58 (2001) 69±79

residues were left lying on the surface. Weeds were

controlled by spot applications of herbicides in the

no-till and mulch-till systems.

Ammonium nitrate and poultry litter were applied

immediately before cotton seeding. The poultry litter

was broadcasted by hand and incorporated to a depth

of 5 cm by pre-plant cultivation in the conventional

and mulch-till systems. In no-till system, the poultry

litter was not incorporated. The poultry litter used in

the study contained 27 and 30 g kgÿ1 N in 1997 and

1998, respectively. A 60% factor (Bitzer and Sims,

1988) was used to adjust for N availability from the

poultry litter during the ®rst year of application. All

plots received a blanket application of 336 kg haÿ1 of

0±20±20 fertilizer resulting in 67 kg haÿ1 of P2O5 and

K2O to nullify the effects of P and K applied through

poultry litter.

The winter rye cover crop, var. OklonTM, was

planted on 4 December 1996 and 24 November

1997, and killed by RoundupTM herbicide (glypho-

sate) on 8 April 1997 and 28 February 1998. A no-till

planter was used to seed the rye cover crop into the

previous cotton stubble immediately after cotton har-

vest. Cotton variety Deltapine NuCotn 33BTM was

seeded in all plots except in the bare fallow treatment,

using a no-till planter. A herbicide mixture of ProwlTM

(pendimethalin) at 2.3 l haÿ1, CotoranTM (¯uome-

turon) at 3.5 l haÿ1, and Gramoxone ExtraTM (para-

quat) at 1.7 l haÿ1 was applied to all plots for weed

control before seeding on 8 May 1997 and 5 May

1998. In addition, all plots received 5.6 kg haÿ1 of

TemikTM (aldicarb) for the control of thrips.

The quantity of residues (dry weight basis) from

cotton, winter rye cover crop, and poultry litter added

to the cotton plots under different tillage, cropping and

N treatments from 1996 to 1998 is shown in Table 2.

2.2. Soil data collection and analysis

Soil samples were collected from the experimental

plots before rye seeding in fall 1996 to determine soil

chemical status before imposing the treatments

(Table 3). Twenty-four soil cores, each 5 cm in dia-

meter, were randomly collected from each of the four

replications using a tractor powered hydraulic probe.

The soils were composited by replication and by

depths of 0±15, 15±30, 30±60, and 60±90 cm. After

starting the experiment, each year, before seeding and

after harvesting of cotton, four soil cores were col-

lected from the four central rows of each plot and

composited by plot and by depths as before. During

the season at cotton ¯owering, four soil cores were

collected from the four central rows of each plot using

a hand held auger and composited by depths of 0±15

and 15±30 cm. The soils were air dried and ground to

pass through a 2 mm sieve before analysis.

Soil pH was measured using a glass electrode

connected to the Orion A290 pH meter (Orion

Table 1

Mean monthly temperature and rainfall, and cumulative irrigation data, Belle Mina, AL, 1997 and 1998

Month Temperature (8C) Rainfall (mm) Irrigation (mm)

1997 1998 Meana 1997 1998 Meanb 1997 1998

January 10 11 3 175 218 153 ± ±

February 13 12 5 130 194 146 ± ±

March 20 15 10 101 129 183 ± ±

April 21 21 16 121 130 130 ± ±

May 25 29 20 108 122 122 23 47

June 27 33 24 195 111 111 23 95

July 33 33 26 51 133 133 101 143

August 31 32 25 121 54 104 195 143

September 30 33 22 176 26 109 218 143

October 23 26 16 229 41 90 ± ±

November 13 18 10 69 86 132 ± ±

December 10 13 5 128 250 158 ± ±

a Adjusted long-term mean.b 70-year mean.

E.Z. Nyakatawa et al. / Soil & Tillage Research 58 (2001) 69±79 71

Research, Boston, MA) in a 1:1 soil:water suspension.

SOM was determined by the wet oxidation method of

Walkley and Black (1934). The soil NH4 and NO3

were measured colorimetrically using the BIO-RAD

Model 550 Microplate Reader (Bio-Rad Laboratories,

Hercules, CA) after extraction in a 1:10 soil: 1 M

KCl solution (Keeney and Nelson, 1982; Sims et al.,

1995). The extractable P was also determined

colorimetrically using the Microplate Reader after

extraction in a 1:10 soil:Mehlich III solution (Murphy

and Riley, 1962; Mehlich, 1984). Measurements

for both N and P were made with a 655 nm wave-

length ®lter with the reference ®lter set at 415 nm

(Murphy and Riley, 1962). The microplate reader

determined concentrations were corroborated with

ion chromatography and inductively coupled plasma

analyses.

2.3. Data analysis

The data were statistically analyzed using the gen-

eral linear model procedures using the statistical

analysis system (SAS Institute, 1987). Contrast pro-

cedures were used to compare the main effect treat-

ment means for tillage systems, cropping systems, and

N treatments.

3. Results and discussion

3.1. Effect of tillage systems

After cotton harvest in November 1998, SOM

in the 0±15 cm soil depth in no-till and mulch-till

system plots was 22 and 27%, respectively, higher

Table 2

Residues from winter rye cover crop, cotton, and poultry litter added to the soil in conventional till (CT), mulch-till (MT), and no-till (NT)

tillage systems; cotton±winter fallow (CF) and cotton±rye sequential (CR) cropping systems, and ammonium nitrate (AN) and poultry litter

(PL) sources of N, Belle Mina, AL, 1996 and 1998 (BF: bare fallow)

Tillage systems

(kg haÿ1)

Cropping systems

(kg haÿ1)

N treatments

(kg haÿ1)

CT MT NT BF CF CR 0 N 100 AN 100 PL 200 PL

Cotton crop

November 1996 22800 22800 22800 0 22800 22800 22800 22800 22800 22800

November 1997 15000 17400 21400 0 18500 18300 12800 21000 14700 26900

Winter rye cover crop

April 1997 10300 10300 10300 0 0 10300 10300 10300 10300 10200

April 1998 9800 12200 16800 0 0 13600 8100 11500 13400 21500

Poultry litter

April 1997 10000 10000 10000 0 10000 10000 0 0 6600 13500

April 1998 8700 8700 8700 0 8700 8700 0 0 5400 11900

Total 76600 81400 90000 0 60000 83700 54000 65600 73200 106800

Table 3

Soil chemical properties (standard errors in parenthesis) in cotton plots prior to imposing tillage, cropping system, and N fertilizer treatments,

Belle Mina, AL, November 1996

Soil depth (cm) pH (1:1 soil:water) Organic matter (g kgÿ1) NH4 (mg kgÿ1) NO3 (mg kgÿ1) P (mg kgÿ1)

0±15 6.2 (0.1) 14.7 (3.9) 80 (10) 35 (10) 44 (7)

15±30 6.2 (0.0) 13.6 (5.6) 110 (4) 22 (5) 38 (9)

30±60 5.7 (0.1) 4.3 (3.2) 55 (8) 37 (15) 8 (8)

60±90 5.3 (0.2) 2.2 (2.4) 59 (8) 42 (14) 3 (6)

72 E.Z. Nyakatawa et al. / Soil & Tillage Research 58 (2001) 69±79

�P < 0:001� than that in conventional till system plots

and 57 and 64%, respectively, higher than that in bare

fallow plots (Table 4). Compared to the beginning of

the experiment in November 1996, mulch-till and no-

till system plots had 50% higher SOM in the 0±15 cm

soil depth in November 1998. Similar results were

found in the 15±30 cm depth (Table 4). A total of 75,

81, and 90 Mg haÿ1 of dry residues from cotton and

winter rye cover crop and poultry litter were added to

conventional till, no-till and mulch-till plots, respec-

tively, from 1996 to 1998 (Table 2). Therefore, the

increase in SOM can be explained by the large amount

of crop and poultry litter residues added to the soil and

the reduced biological oxidation of organic C to CO2

in no-till and mulch-till system plots. A similar result

was reported by Rasmussen et al. (1998).

The low SOM in bare fallow plots was attributed to

lack of residues, which add SOM to the soil, similar to

the results of Peterson et al. (1998). No-till and mulch-

till results in the strati®cation of SOM, with a higher

concentration in the top upper soil layers (Alvarez

et al., 1995), which explains the lack of signi®cant

differences in SOM among the tillage systems in the

30±90 cm soil depth. Our results for the no-till system

with cotton are in agreement with those of Dick

(1983), Kern and Johnson (1993), and Campbell

et al. (1996), who also found an increase in SOM

in the top 15 cm of the soil because of no-till in cereal-

based cropping systems. Similarly, Alvarez et al.

(1995) found a 42±45% higher SOM in the top

5 cm of the soil in a wheat-soybean cropping system

in no-till plots as compared with plow and chisel

tillage plots.

Most studies show that stable SOM levels are

generally achieved after several years depending on

the crop management system, soil type and environ-

mental conditions (Hendrix et al., 1998). Although

results from our study do not indicate stable SOM

levels, the improved SOM signi®cantly improved

cotton germination, establishment, and growth

through soil water conservation in the top 7 cm of

the soil under drought conditions (Nyakatawa and

Reddy, 2000; Nyakatawa et al., 2000).

The NH4 concentration before cotton seeding in

April 1997 in the 0±15 (94 mg kgÿ1) and 15±30 cm

(104 mg kgÿ1) soil depths in bare fallow tillage sys-

tem plots was, respectively, 49 and 69% higher

�P < 0:05� than that in other tillage system plots

(Fig. 1). Also, in November 1997, April 1998, and

November 1998, NO3 concentration in bare fallow

plots in the 0±60 cm soil depth (25±75 mg kgÿ1) was

38±100% higher �P < 0:01� than that in the other

tillage system plots. These results are due to N-uptake

by the rye cover crop during winter and early spring

Table 4

SOM at different soil depths as in¯uenced by conventional till (CT), mulch-till (MT), and no-till (NT) tillage systems and cotton±winter fallow

(CF) and cotton±rye sequential (CR) cropping systems, Belle Mina, AL, 1996±1998 (BF: bare fallow)a

Tillage systems (g kgÿ1) Cropping systems (g kgÿ1)

CT MT NT BF CF CR

0±15 cm

November 1996 15 a 15 a 15 a 15 a 15 a 15 a

November 1998 18 b 23 c 22 c 14 a 18 b 22 c

15±30 cm

November 1996 14 a 14 a 14 a 14 a 14 a 14 a

November 1998 14 b 18 c 16 c 10 a 12 a 17 b

30±60 cm

November 1996 4 a 4 a 4 a 4 a 4 a 4 a

November 1998 5 a 6 b 5 a 4 a 6 a 5 a

60±90 cm

November 1996 2 a 2 a 2 a 2 a 2 a 2 a

November 1998 2 b 2 b 2 b 1 a 2 a 2 a

a Means for tillage or cropping systems in the same row and soil depth followed by the same letter are not signi®cantly different at the 5%

level.

E.Z. Nyakatawa et al. / Soil & Tillage Research 58 (2001) 69±79 73

and by the cotton crop in conventional till, mulch-till,

and no-till system plots during the summer and also to

immobilization of inorganic N to SOM. High mine-

ralization of organic N associated with mulch-till may

account for the three times more NH4 compared with

the no-till system plots in the 15±30 cm soil depth in

April and November 1998 (Fig. 1).

At the beginning of the experiment in April 1997,

mean NO3 concentration for all tillage systems in the

60±90 cm soil depth was twice (66 mg kgÿ1) that in

the 0±30 cm soil depth (Fig. 1), most likely due to

leaching of residual NO3 from the upper soil layers in

the previous cropping year. However, there was a

steady decline in NO3 accumulation in the 30±

90 cm soil depth in conventional till, mulch-till, and

no-till system plots from April 1997 to November

1998, most likely, a result of N-uptake in the 0±30 cm

soil depth, which reduced the amount of nitrate avail-

able for leaching into the deeper soil layers. However,

in the bare fallow plots, NO3 concentration in each soil

depth remained relatively high compared with the

other tillage system plots since there was no crop to

use the N. Although more NO3 may accumulate in

conventional till versus no-till system plots (Eck and

Jones, 1992), our results did not show any signi®cant

differences in soil NO3 between conventional till and

no-till system plots in the 30±60 and 60±90 cm soil

depths.

Unlike NO3, which was highest in the 60±90 cm

soil depth, extractable soil P at each sampling stage

was highest in the 0±30 cm soil depth (Fig. 2). This

was because P moves much slower than NO3 (Gutier-

rez-Boem and Thomas, 1998). Extractable P concen-

tration in bare fallow plots before cotton planting in

Fig. 1. Soil NH4 and NO3 in cotton plots as affected by conventional till (CT), mulch-till (MT), no-till (NT), and bare fallow (BF) tillage

systems, Belle Mina, AL, 1996±1998.

74 E.Z. Nyakatawa et al. / Soil & Tillage Research 58 (2001) 69±79

April 1997 (20 mg kgÿ1) was 92±130% lower than

that in plots under the other tillage systems (Fig. 2).

After cotton harvest in November 1998, extractable P

concentration in no-till and bare fallow plots in the

0±30 cm soil depth (17±33 mg kgÿ1) was 55±70% less

than that in conventional till and mulch-till plots,

respectively. Similar results were observed in the

60±90 cm soil depth (Fig. 2), suggesting that no-till

can reduce overloading of P in surface soils. In the

30±60 and 60±90 cm soil depths, extractable P con-

centration with conventional till (12±17 mg kgÿ1) and

mulch-till (23±26 mg kgÿ1) in November 1998 was

100±200% higher than that at the beginning of the

study in November 1996, respectively, whereas

extractable P concentrations in no-till and bare fallow

plots in November 1998 were equal or lower than in

November 1996. As with N, these results can be

attributed to a slow rate of mineralization of crop

residues in no-till plots and to the absence of residues

in bare fallow plots.

Within each soil depth, there was no signi®cant

change in soil pH due to treatments, which ranged

from 5.0 to 6.0 (data not shown). However, Kingery

et al. (1994) reported that long-term poultry litter

application to tall fescue (Festuca arundanacea

Schreb) increased soil pH by 0.5 units to a depth of

60 cm in north Alabama. Our results did not show

signi®cant differences in pH most probably due to the

high buffering capacity of the soil and possibly the

short duration of the study.

3.2. Effects of cropping system

The greatest source of SOM is the residue contri-

buted by the crops. Consequently, the cropping system

and the method of crop residue management are

Fig. 2. Extractable soil P in cotton plots as affected by conventional till (CT), mulch-till (MT), no-till (NT), and bare fallow (BF) tillage

systems, and N levels (kg haÿ1) from ammonium nitrate (AN) and poultry litter (PL), Belle Mina, AL, 1996±1998.

E.Z. Nyakatawa et al. / Soil & Tillage Research 58 (2001) 69±79 75

equally important in SOM improvement. In November

1998, SOM in the 0±15 and 15±30 cm soil depths had

increased by 62 and 27% over that in November 1996

due to winter rye cover cropping, respectively

(Table 4). SOM in the cotton±rye sequential cropping

system in the 0±15 cm soil depth was 22% higher

�P < 0:0001� than in the cotton±winter fallow crop-

ping system in November 1998. A total of 84 Mg haÿ1

of residues were added to the soil with cotton±winter

rye cropping compared with 60 Mg haÿ1 with cotton±

winter fallow cropping from 1996 to 1998 (Table 2).

The above results indicate the importance of the

winter rye cover crop as a source of crop residues

needed to improve SOM in the plow layer under

conservation tillage systems.

The NH4 and NO3 concentrations in the cotton±rye

sequential cropping system before cotton seeding in

April 1997 in the 0±30 cm soil depth (30±60 mg kgÿ1)

were 23±82% lower than in the cotton±winter fallow

cropping system, respectively (Fig. 3). This was attri-

buted to N-uptake by the rye cover crop and to N

immobilization by soil microbes during the early

stages of winter rye residue decomposition. A similar

result was reported by Knowles et al. (1993), who

found less soil NO3 when seeding wheat in sorghum

(Sorghum bicolor L.) residues due to microbial immo-

bilization of N. Sainju et al. (1998) also reported lower

soil NO3 concentration following a rye cover crop due

to its high root density, which removed a considerable

amount of NO3 from the soil.

Increasing the cropping intensity by growing two or

more crops per year resulted in signi®cantly lower soil

NO3 levels despite additions through N fertilizer

(Wood et al., 1991). Therefore, the decline in NO3

accumulation in each soil depth, and more so in the

30±90 cm soil depths from November 1996 to 1998

Fig. 3. Soil NH4 and NO3 in cotton plots as affected by cotton±winter fallow (CF), and cotton±rye sequential cropping systems (CR), Belle

Mina, AL, 1996±1998.

76 E.Z. Nyakatawa et al. / Soil & Tillage Research 58 (2001) 69±79

may be due N-uptake by the cotton and winter rye

crops. The scavenging of residual NO3 after harvest of

the main crop in the fall by the winter cover crop

reduces the amount available for leaching. In April

1998, NH4 in the cotton±rye sequential cropping

system in the 0±15 and 15±30 cm soil depths (30±

41 mg kgÿ1) was, respectively, 25 and 70% higher

than in the cotton±winter fallow cropping system. This

can be a result of additional NH4 in the soil due to

mineralization of winter rye crop residues and

increased SOM level, which holds the NH4� ions

against leaching.

3.3. Effects of poultry litter

There was a signi®cant effect of 2 years of surface

application of poultry litter to cotton plots on SOM in

the 0±15 cm depth (data not shown). In November

1998, plots that received 100 kg N haÿ1 in the form of

poultry litter had 21 and 35% higher �P < 0:0001�SOM (23 g kgÿ1) than those that received 100 kg N

haÿ1 in the form of ammonium nitrate (19 g kgÿ1) and

0 N (17 g kgÿ1), respectively. Similar ®gures for plots

that received 200 kg N haÿ1 in the form of poultry

litter were 55 and 80%, respectively. Kingery et al.

(1994) also found signi®cant increases in SOM in the

top 15 cm of the soil due to poultry litter application to

perennial tall fescue.

A total of 54, 66, 73, and 106 Mg haÿ1 of residues

were added to the soil under 0, and 100 kg N haÿ1

ammonium nitrate, 100, and 200 kg N haÿ1 poultry

litter treatments, respectively, from 1996 to 1998

(Table 2). In addition to the large amount of crop

residues produced with poultry litter application, the

increase in SOM in the top 15 cm of the soil can be

explained by the fact that the surface applied poultry

litter is not subjected to rapid microbial decomposition

that occurs when it is soil incorporated. Our results

showing higher SOM in poultry litter compared with

inorganic N are similar to those of Rasmussen et al.

(1998). In addition to increasing residue production,

manure can increase soil organic C by 30±80%

through the direct addition of C.

In April 1998, the NH4 concentration in the 30±

60 cm soil depth in plots that received 200 kg N haÿ1

in the form of poultry litter was two to three times

higher than that for the other N levels (Fig. 4).

When converted to NO3, the NH4 can cause leaching

problems. Nitrate contamination of groundwater is a

problem that has been associated with excessive

application of poultry litter to crop lands. The limit

for groundwater nitrate N concentration set by the

environmental protection agency (EPA) is 10 mg lÿ1.

According to Liebhardt et al. (1979), applying poultry

litter to crop lands at rates greater than 13.5 Mg haÿ1

consistently resulted in groundwater nitrate levels in

excess of the EPA limit.

Residual soil NO3 concentration under all fertilizer

treatments in the 60±90 cm soil depth before cotton

seeding in April 1997 (63±71 mg kgÿ1) was about

twice that in the 0±60 cm soil depth (Fig. 4). However,

after cotton harvest in November 1997, the NO3 was

uniformly distributed in each soil depth, suggesting

that the high NO3 content in the 60±90 cm soil depth

had most likely been depleted by plant uptake and

leaching. Our results did not indicate any signi®cant

differences in NH4 concentration in plots that received

100 kg N haÿ1 in the form of ammonium nitrate or

poultry litter.

In November 1997, NO3 concentration in the 0±

15 cm soil depth in plots that received 100 kg N haÿ1

in the form of poultry litter (41 mg kgÿ1) was 40%

higher �P < 0:05� than in plots that received

100 kg N haÿ1 in the form of ammonium nitrate. A

similar result was obtained in the 15±30 cm soil depth,

indicating that poultry litter may contribute more N to

the soil, which may be a source of NO3 pollution.

Similar accumulation of NO3 in the soil after applica-

tion of poultry litter was reported in plots with tall

fescue by Kingery et al. (1994). However, compared to

November 1996, the NO3 levels of November 1998 do

not show a signi®cant build up of NO3 in the soil

pro®le due to use of poultry litter, probably due to N-

uptake by cotton and the winter rye cover crop, a

combination of dicot and monocot crops. Further, to

improve its ef®ciency of N-uptake, the winter rye

cover crop was not fertilized.

A major concern with the use of poultry litter on

crop lands is a possible buildup of P in the soil. Our

results showed a 46% higher �P < 0:05� extractable P

concentration in the 0±15 cm soil depth (74 mg kgÿ1)

in plots that received 200 kg N haÿ1 in the form of

poultry litter compared to control plots in April 1998,

before planting cotton (Fig. 2). However, the P

levels were in the normal range for the cotton

plots. After cotton harvest in November 1998, the P

E.Z. Nyakatawa et al. / Soil & Tillage Research 58 (2001) 69±79 77

concentrations in the 0±30 cm soil depth had fallen to

levels equal to or lesser than those at the beginning of

the experiment in November 1996. This suggest that,

in the short term, P-uptake by the cotton and winter rye

crops were able to prevent a build up of P in the soil.

Kingery et al. (1994) reported over six times higher

extractable P to a depth of 60 cm due to long-term

application of poultry litter to tall fescue. Therefore,

more years of data collection may be required to

establish the P level and time period after which P

input by poultry litter will outweigh P uptake in cotton

production systems.

4. Conclusions

Results from this study show that no-till and mulch-

till conservation tillage systems, winter rye cover

cropping, and surface application of poultry litter to

cotton plots can rapidly increase surface SOM. This

increase was attributed to the large quantities of

residues from the winter rye cover crop, the cotton

crop, and the surface applied poultry litter. Although,

it is not known how long these differences will persist,

short term bene®ts of increased surface SOM such as

improved soil water conservation, seedling establish-

ment, crop growth, and yield were clearly visible in

this study. Surface application of poultry litter may

cause NO3 and P buildup in the soil, although uptake

of P by winter rye and cotton crops prevented a

signi®cant build up of these nutrients in this study.

Acknowledgements

The authors acknowledge the ®nancial assistance of

the USDA/CSREES (Grant No. 96-38814-2845) in

conducting the research reported herein.

Fig. 4. Soil NH4 and NO3 in cotton plots as affected by N levels (kg haÿ1) from ammonium nitrate (AN) and poultry litter (PL), Belle Mina,

AL, 1996±1998.

78 E.Z. Nyakatawa et al. / Soil & Tillage Research 58 (2001) 69±79

References

Alvarez, R., Diaz, R.A., Barbero, N., Sanatanatoglia, O.J., Blotta,

L., 1995. Soil organic carbon, microbial biomass and CO2-C

production from three tillage systems. Soil Till. Res. 33,

17±28.

Alvarez, R., Russo, M.E., Prystupa, P.J., Scheiner, D., Blotta, L.,

1998. Soil carbon pools under conventional and no-tillage

systems in the Argentine Rolling Pampa. Agron. J. 90,

138±143.

Bitzer, C.C., Sims, J.T., 1988. Estimating the availability of

nitrogen in poultry manure through laboratory and ®eld studies.

J. Environ. Qual. 17, 47±54.

Burgess, M.S., Mehuys, G.R., Madramootoo, C.A., 1996. Tillage

and crop residue effects on corn production in Quebec. Agron.

J. 88, 792±797.

Campbell, C.A., McConkey, B.G., Zentner, R.P., Selles, F., Curtin,

D., 1996. Tillage and crop rotation effects on soil organic C and

N in a coarse-textured Typic Haploboroll in southwestern

Saskatchewan. Soil Till. Res. 37, 3±14.

Christensen, N.B., Lindemann, W.C., Salazar-Sosa, E., Gill, L.R.,

1994. Nitrogen and carbon dynamics in no-till and stubble

mulch tillage systems. Agron. J. 86, 298±303.

Dick, W.A., 1983. Organic carbon, nitrogen, and phosphorus

concentrations and pH in soil pro®les as affected by tillage

intensity. Soil Sci. Soc. Am. J. 47, 102±107.

Eck, H.V., Jones, O.R., 1992. Soil nitrogen status as affected by

tillage, crops, and crop sequences. Agron. J. 84, 660±668.

Gutierrez-Boem, F.H., Thomas, G.W., 1998. Phosphorus nutrition

affects winter wheat response to water de®cit. Agron. J. 90,

166±171.

Hendrix, P.F., Franzluebbers, A.J., McCracken, D.V., 1998.

Management effects on C accumulation and loss in soils of

the southern Appalachian Piedmont of Georgia. Soil Till. Res.

47, 245±251.

Keeney, D.R., Nelson, D.W., 1982. Nitrogen-inorganic. In: Page,

A.L., Miller, R.H., Keeney, D.R. (Eds.), Methods of Soil

Analysis. Part 2. Chemical and Microbial Properties, 2nd

Edition. American Society of Agronomy, Madison, WI,

pp. 643±659.

Kern, J.S., Johnson, M.G., 1993. Conservation tillage impacts on

national soil and atmospheric carbon levels. Soil Sci. Soc. Am.

J. 57, 200±210.

Kingery, W.L., Wood, C.W., Delaney, D.P., Williams, J.C., Mullins,

G.L., 1994. Impact of long-term land application of broiler

litter on environmentally related soil properties. J. Environ.

Qual. 23, 139±147.

Knowles, T.C., Hipp, B.W., Graff, P.S., Marshall, D.S., 1993.

Nitrogen nutrition of winter rainfed winter wheat in tilled

and no-till sorghum and wheat residues. Agron. J. 85,

886±893.

Lamb, J.A., Peterson, G.A., Fenster, C.R., 1985. Wheat fallow

tillage systems' effect on a newly cultivated grassland soils'

nitrogen budget. Soil Sci. Soc. Am. J. 49, 352±356.

Liebhardt, W.C., Golt, C., Tupin, J., 1979. Nitrate and ammonium

concentrations of ground water resulting from poultry manure

applications. J. Environ. Qual. 8, 211±215.

Mehlich, A., 1984. Mehlich 3 soil extractant. Commun. Soil Sci.

Plant Anal. 15, 1409±1416.

Murphy, J., Riley, J.P., 1962. A modi®ed single solution method for

determining phosphate in natural waters. Anal. Chim. Acta 27,

31±36.

Nyakatawa, E.Z., Reddy, K.C., 2000. Tillage, cover cropping, and

poultry litter effects on cotton. I. Germination and emergence.

Agron. J. 92, 992±999.

Nyakatawa, E.Z., Reddy, K.C., Mays, D., 2000. Tillage, cover

cropping, and poultry litter effects on cotton. II. Growth and

yield parameters. Agron. J. 92, 1000±1007.

Peterson, G.A., Halvorson, A.D., Havlin, J.L., Jones, O.R., Lyon,

D.J., Tanaka, D.L., 1998. Reduced tillage and increasing

cropping intensity in the Great Plains conserves soil C. Soil

Till. Res. 47, 207±218.

Rasmussen, P.E., Albrecht, S.L., Smiley, R.W., 1998. Soil C and N

changes under tillage and cropping systems in semi-arid Paci®c

Northwest agriculture. Soil Till. Res. 47, 197±205.

Sainju, U.M., Singh, B.P., Whitehead, W.F., 1998. Cover crop root

distribution and its effects on soil nitrogen cycling. Agron. J.

90, 511±518.

SAS Institute, 1987. SAS System for Personal Computers, Release

6.04. SAS Institute, Inc., Cary, NC.

Schindler, D.W., 1977. Evolution of phosphorus limitation in lakes.

Science 195, 260±262.

Sharpley, A.N., Daniel, T.C., Sims, J.T., Pote, D.H., 1996.

Determining environmentally sound soil phosphorus levels. J.

Soil Water Conserv. 51, 160±166.

Sims, G.K., Ellsworth, T.R., Mulvaney, R.L., 1995. Microscale

determination of inorganic nitrogen in water and soil extracts.

Commun. Soil Sci. Plant Anal. 26, 303±326.

Stevenson, F.J., 1986. Cycles of Soil. Wiley, New York.

Unger, P.W., 1991. Organic matter, nutrient, and pH distribution in

no- and conventional tillage semi-arid soils. Agron. J. 83, 186±

189.

US Environmental Protection Agency, 1996. Environmental

indicators of water quality in the United States. EPA 841-R-

96-002.

Walkley, A., Black, I.A., 1934. An examination of the Defjaroff

method for determining soil organic matter and a proposed

modi®cation of the chromic acid titration methods. Soil Sci. 37,

29±38.

Wood, C.W., Westfall, D.G., Peterson, G.A., 1991. Soil carbon and

nitrogen changes on initiation of no-till cropping systems. Soil

Sci. Soc. Am. J. 55, 470±476.

E.Z. Nyakatawa et al. / Soil & Tillage Research 58 (2001) 69±79 79