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WASTE MANAGEMENT

Tillage, Cover Cropping, and Poultry Litter Effects on Cotton

II. Growth and Yield Parameters

Dep. of Plant and Soil Science, Alabama A&M Univ., P.O. Box 1208, Normal, AL 35762 USA

reddyc{at}aamu.edu

	ABSTRACT

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
The development of conservation tillage systems for cotton (Gossypium hirsutum L.), capable of reducing soil erosion and improving soil quality while increasing yields and profits, remains a challenge in the southeastern USA. Poor emergence and growth, delayed maturity, and reduced yield are some of the problems that have been encountered in the use of conservation tillage on cotton. The objectives of this study was to evaluate the effects of tillage (no-till, mulch-till, conventional till), cropping system [cotton–winter fallow, cotton–winter rye (Secale cereale L.) cover crop] and N source (poultry litter, ammonium nitrate) on growth and yield of cotton from 1996 to 1998 in northern Alabama. In 1997, cotton lint yield under no-till (NT) was 24 and 18% greater than that under conventional till (CT) and mulch-till (MT) systems, respectively. In 1998, cotton lint yield under the NT system was 7% greater than that under CT. Poultry litter (PL) at 100 kg N ha^-1 gave similar lint yield to ammonium nitrate (AN), whereas at 200 kg N ha^-1, lint yields were significantly greater. No-till, cotton–winter rye cropping, and surface application of 200 kg N ha^-1 in form of PL conserved soil moisture in the top 7 cm of the soil. This resulted in early seedling emergence, high seedling vigor, good plant growth, and high lint yield of cotton. These treatments would be appropriate for use in the southeastern USA where soil erosion is a problem and plenty of PL is available each year from the poultry industry.

Abbreviations: AN, ammonium nitrate • CC, cotton–winter fallow • CR, cotton-winter rye • CT, conventional till • LAI, leaf area index • MT, mulch-till • NT, no-till • PL, poultry litter

	INTRODUCTION

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
COTTON (Gossypium hirsutum L.) production under conventional till (CT) is still the most common practice in many areas of the southeastern and mid-southern USA. Conventional till systems in northern Alabama include shredding the cotton stalks, primary tillage with moldboard or chisel plow in the fall, spring disking or harrowing, and inter-row cultivation for weed control during the cotton growing season. These tillage operations, which may be 12 to 15 in number per season (Keeling et al., 1989), make the soil susceptible to erosion and hasten the depletion of soil organic matter (Morrison et al., 1990; Burgess et al., 1996; Bordovsky et al., 1998).

No-till can reduce tillage operations by as many as six to eight operations (Bradley, 1993; unpublished), which reduce machinery, fuel, and labor costs and increases machinery life and profits (Keeling et al., 1989). In addition, no-till can reduce soil erosion while maintaining or increasing soil productivity (Stevens et al., 1992; Triplett et al., 1996). However, some farmers who have tried to adopt conservation tillage systems for cotton production in compliance with the 1985 and 1990 Farm Bills (Federal Register, 1987; Food, Agriculture, Conservation, and Trade Act, 1990) have faced some problems. Cotton seedlings are generally weak and conservation tillage can result in poor seedling establishment and poor crop growth due to soil compaction, resulting in static or reduced cotton yields (Delaney, 1991; Schertz and Kemper, 1994; Raper et al., 1998).

Use of cover crops such as winter rye and organic soil amendments such as poultry litter (PL) in conservation tillage systems may increase soil organic matter levels, which in turn would reduce compaction and conserve soil moisture. This could improve cotton seedling emergence and plant growth. In many cases, the cover crop is killed 2 to 3 wk. ahead of cotton planting to enable the soil to warm up. Legumes are often unsuitable for use as cover crops in no-till cotton production in north Alabama, because they are difficult to kill, thus delaying cotton planting and reducing yields (Anonymous, 1991a). In addition, the N produced by legumes can be injurious to cotton seedlings due to ammonia toxicity, especially in high pH soils (Meige et al., 1967). Rye is a good alternative for legumes in no-till cotton production systems. The attributes that make winter rye a superior cover crop over legumes include vigorous growth, winter hardiness, early spring growth, herbicide sensitivity, and mulch persistence (Brown et al., 1985; Delaney, 1991). Winter rye cover crops may also reduce leaching losses of residual N fertilizer (Meisinger et al., 1991; Kelly et al., 1992), which may contribute to ground water pollution.

Poultry litter is a relatively inexpensive source of nutrients, particularly N and P. Application of PL to croplands provides an environmentally friendly way of disposing of the large quantities of PL produced on poultry farms in several southeastern states. The Sand Mountain region of Alabama, which is adjacent to the intensive cotton producing areas of northern Alabama, produces nearly 1.8 million Mg of PL annually (Kingery et al., 1994). Therefore, the cotton producing Tennessee Valley region of northern Alabama has a great potential for benefitting from using PL as a fertilizer. The objectives of this study were to evaluate the effects of no-till and mulch-till with winter rye cover cropping and PL on cotton growth and yield on a Decatur silt loam soil (fine, kaolinitic, thermic Rhodic Paleudults) in North Alabama.

	Materials and methods

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
Details on study site, treatments, cotton and winter rye planting, fertilizer, and poultry litter application are presented in the preceding paper (Nyakatawa and Reddy, 2000).

Crop Management
During the season, a cultivator was used for controlling weeds in the conventional till system while spot applications of Roundup using a knapsack sprayer were used to control weeds in the no-till and mulch-till systems. No major weed problems were observed in the cotton plots. The major insect pests observed in cotton were aphids (Aphis spp.) and bollworms (Heliothis spp.). Aphids were controlled by spraying Bidrin [dicrotophos, (E)-2-dimethylcarbamoyl-1-methylvinyl dimethyl phosphate] at 0.4 kg ha^-1, whereas bollworms were controlled with Karate [cypermethrin, (±)--cyano-3-phenoxybenzyl (±)-cis,trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate]. The growth regulator Pix (1,1-dimethylpiperidinium chloride), at 0.8 kg ha^-1, was applied to cotton to reduce vegetative growth at 2.5 mo after planting. The cotton was defoliated with a mixture of Finish [a mixture of ethephon ((2-chloroethyl) phosphoric acid) and cyclanilide (1-(2,4-dichlorophenylaminocarbonly) cyclopropane carboxylic acid] at 2.3 L ha^-1 and Def (S,S,S-tributyl phosphorotrithioate) at 0.6 kg ha^-1 2 wk before the first harvest.

Data Collection
Baseline soil samples were collected from the experimental plots before rye seeding in the Fall of 1996 to determine the soil chemical status before imposing the treatments. Twenty-four soil cores, 5 cm in diameter, were randomly collected from each of the four replications using a tractor operated hydraulic auger. The soils were composited by replication and by depths of 0 to 15, 15 to 30, 30 to 60, and 60 to 90 cm. The pH of the soil in the 0 to 30 cm soil depth was 6.16, while organic matter, NH₄, NO₃, and extractable P concentrations were 14.2 g kg^-1, and 80.4, 34.6, and 43.5 mg kg^-1, respectively. Soil pH was measured using a glass electrode connected to an Orion A290 pH meter (Orion Research, Boston, MA) in a 1:1 soil/water suspension. Soil organic matter 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/0.1 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; Olsen and Dean, 1965; Mehlich, 1984). Measurements for both N and P were made at 655 nm wavelength filter with the reference filter set at 415 nm (Murphy and Riley, 1962). The microplate reader determined concentrations were corroborated with ion chromatography (IC) and inductively coupled plasma (ICP) analyses.

Crop data collected were: days to squaring, days to flowering, days to maturity, plant height, leaf area index (LAI), canopy cover, surface root biomass, number of squares per plant at boll formation, number of bolls per plant at harvest, leaf N concentration, shoot biomass, and seed cotton yield. Data on plant height, number of squares per plant, and number of bolls per plant were taken on three randomly selected plants from the central four rows of each plot. Leaf area index was measured from the central four rows of each plot using the AccuPAR linear ceptometer (Decagon Devices, Pullman, WA). Canopy cover was determined by measuring the width of the crop canopy of each row from the four central rows on each plot using a ruler and expressing the figure as a percentage of the row width. Shoot and root biomass were determined by sampling plants with their roots intact from 0.5-m² quadrants from each plot. Roots were extracted out of the soil by removing soil from both sides of the row and lifting the intact plants from the base with a garden fork. The roots were cut from the shoots, washed in water to remove the soil, and placed in separate bags. The shoot and root samples were oven-dried to constant weight at 65°C for 72 h before weighing. Data for plant height, LAI, canopy cover, surface root biomass, leaf N concentration, and shoot biomass were taken at the maximum crop growth stage, which was at 50% flowering.

Leaf N concentration was determined by sampling a total of 15 fully developed leaves just below the growing tip on main branches of three plants in the central four rows. The leaves were washed in 0.3% v/v detergent solution followed by rinsing with distilled water to remove dust and any other surface contaminants. After rinsing, the leaves were dried in a laboratory oven at 65°C for 72 h, after which they were ground to pass through a 2-mm sieve using a Wiley mill (A.H. Thomas Co., Philadelphia, PA). The leaves were stored in sealed plastic bags in a freezer before analysis. Total N concentration of the samples was determined by digesting 0.1 g of plant material with 5 mL mixture of 350 mL concentrated H₂SO₄, 420 mL 30% H₂O₂, 0.42 g Se powder, and 14 g LiSO₄ (Bremner and Mulvaney, 1982), followed by analysis using an automated Kjeltec 1026 Analyzer (Kjeltec, Sweden).

Seed cotton yield was determined by mechanically harvesting open cotton bolls in the central four rows of each plot. The harvest operations were done on 14 Nov. 1997 (first picking) and 19 Nov. 1997 (second picking) and similarly on 30 Sept. and 12 Oct. 1998. The seed cotton was weighed and sent to a nearby gin where the percent cotton lint (ginning percent) was determined. Lint yield data for the treatments were determined by multiplying the seed cotton yield by a ginning percent of 39%. Weather data were taken from an automatic weather station at the Experiment Station.

Data Analysis
The data were analyzed using GLM and contrast analysis procedures of the Statistical Analysis System Version 6.0 (SAS Inst., 1987) were used to compare the main effect treatment means for tillage systems, cropping systems, and N sources as there were no significant interactions between the treatment factors. Regression analysis was used to determine the response functions of growth and yield parameters of cotton to the N levels from PL.

	Results and discussion

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
Drier weather and greater temperatures in the summer of 1998 (Fig. 1) resulted in a faster rate of growth and development of cotton and greater lint yield compared with 1997. For best cotton growth and development, the mean maximum temperature should be around 32°C. Cotton reached squaring, flowering, and maturity stages about 21 d earlier in 1998, which had 5 to 8°C higher temperature compared with 1997 (Table 1 and Fig. 1). The faster rate of growth and development and the 15% higher lint yield of the cotton crop of 1998 compared with 1997 can be explained by more heat units received by the crop in 1998 (Fig. 1). Research on temperature effects on cotton growth and development has shown that rates of cotton seedling germination and emergence, rates of floral initiation, square development, and boll maturation in cotton increase with temperature up to about 32°C (Chu et al., 1991; Reddy et al., 1993; Hodges et al., 1993).

View larger version (36K): [in this window] [in a new window]   Fig. 1 Mean temperature, total monthly rainfall, and cumulative heat units and irrigation water applied to cotton plots, Belle Mina, AL, 1996 to 1998

Stevens et al. (1992) reported that planting no-till cotton into cover crops delayed cotton maturity compared with conventional till in the second and third years of study on a Grenada silt loam soil (fine-silty, mixed, active, thermic Glossic Fragiudalfs) in north Mississippi. However, Triplett et al. (1996) found that no-till cotton produced 70% of the final yield 7, 6, and 10 d earlier in the second, third, and fourth years, respectively, of study on a similar soil type in the same area. In western Tennessee, Hoskinson et al. (1982) reported delayed cotton maturity when planted no-till into heavy cover crops with high rates of N fertilization. In our study, the cover crop was not fertilized to prevent problems of excessive residue reducing soil temperatures, and slowing seedling emergence and growth. The other reason for not fertilizing the cover crop was to enable it to pick up residual nutrients from the cotton crop, which could leach into ground water resources.

Cotton plants under NT and MT were, respectively, 6 and 9 cm taller than those under CT in 1997. However, in 1998, cotton plants under NT were 6 and 11 cm shorter than those under CT and MT, respectively (Table 1). Canopy cover at maturity for cotton under MT was 7% greater than that under NT in 1998. Reduced tillage systems such as NT and MT delay the decay of crop residues, which results in a slower release of N to the soil (Bordovsky et al., 1998). This may be accompanied by immobilization of soil mineral N, thereby reducing its availability to plants. The peak N demand for cotton occurs between flowering and boll set (Anonymous, 1991a; Saranga et al., 1998). Therefore, leaf N concentration at flowering can give an indication of N stress in the cotton plants. Leaf N concentration at flowering for cotton plants under MT and NT were similar to those under CT in 1997. In 1998, leaf N concentration at flowering under MT and NT were, respectively, 4 and 15% greater than those under CT (Table 2) , probably due to better moisture availability under NT and MT treatments.

The results for cotton growth and yield parameters clearly show that NT performed better than MT and CT tillage systems. Improved soil moisture conservation in NT plots was largely responsible for improved lint yields in this system. Soil moisture measurements in the top 7 cm of the soil taken during the first 4 d of cotton seedling emergence showed a greater volumetric soil moisture content in NT plots compared with CT plots in both years (Nyakatawa and Reddy, 2000). As a result, cotton seedling emergence was faster and better in NT plots compared with CT during the dry period at seedling emergence. This resulted in better plant growth and greater yield parameters in cotton, which were correlated to lint yield (Tables 3 and 4) . Research conducted at the Center for Integrated Pest Management at North Carolina State University has shown that there is a strong relationship between environmental factors such as temperature during seedling establishment and subsequent cotton yields (Anonymous, 1991b). Previous research done on the Decatur silt loam soil showed no significant differences in seed cotton yields between no-till and conventional till (Brown et al., 1985). However, results from our study are similar to the findings of Harmen et al. (1989), who found significant increase in cotton lint yield under no-till compared with conventional till on a Sherm clay loam soil (fine, mixed, mesic Torrertic Paleustolls) in Texas. Stevens et al. (1992) found greater seed cotton yields under no-till compared with conventional till in 1 out of 3 yr of study on a Grenada silt loam soil.

Effects of Nitrogen Sources
The cotton crop responded positively to N fertilization with AN and PL. Time to squaring for cotton plants that received 100 kg N ha^-1 in the form of PL was, in both years, 1 d shorter compared with those that received AN (Table 1). Plants that received 100 kg N ha^-1 in the form of PL reached the flowering stage 2 and 1 d earlier than those that received AN in 1997 and 1998, respectively. However, plants that received 100 kg N ha^-1 in the form of AN were 8 and 10 cm taller than those that received it in the form of PL in 1997 and 1998, respectively (Table 1).

In 1997, canopy cover for plants that received 100 kg N ha^-1 in the form of AN was greater than for those that received PL. In both years, plants that received 100 kg N ha^-1 in the form of AN had greater LAI than those that received PL. In 1997, leaf N concentration, root biomass, and shoot biomass for cotton plants that received 100 kg N ha^-1 in the form of AN were 24, 41, and 42% greater than those for plants that received it in the form of PL (Table 2). In 1998, yield parameters for plants that received 100 kg N ha^-1 in the form of AN were similar to those for plants that received it in the form of PL. Plants that received 200 kg N ha^-1 in the form of PL had significantly greater values for height, LAI, bolls per plant, and dry weights compared with those that received 100 kg N ha^-1 in the form of PL (Fig. 2 and 3) . Consequently, lint yield for plants that received 200 kg N ha^-1 in the form of PL was 25 and 38% greater that those that received 100 kg N ha^-1 in the form of PL in 1997 and 1998, respectively. From another experiment at the same site, Negatu et al. (1995) reported that fresh poultry litter gave greater cotton seed yield compared with urea on the Decatur silt soil.

View larger version (33K): [in this window] [in a new window]   Fig. 2 Growth characteristics of cotton as functions of N from poultry litter, Belle Mina, AL, 1997 and 1998 (Error bars = standard error of means)

View larger version (35K): [in this window] [in a new window]   Fig. 3 Leaf N concentration and yield parameters of cotton as functions of N from poultry litter, Belle Mina, AL, 1997 and 1998 (Error bars = standard error of means)

	Conclusions

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
Results from our study indicate that NT significantly increased growth parameters and yield of cotton. The effects of the winter rye cover crop on cotton lint yield were not significant. However, significant improvement in cotton growth and yield parameters due to winter rye cover cropping were observed in the second year. Poultry litter at 100 kg N ha^-1 gave similar lint yields to AN. However, at 200 kg N ha^-1 lint yields were significantly greater than those at 100 kg N ha^-1 from AN or PL. In practical terms, NT, cover cropping, and surface application of PL at 200 kg N ha^-1 into crop residues will be useful for soil moisture conservation in cotton production systems in the southeastern USA where erosion is a problem, abundant PL is available, and its disposal is becoming a problem.Food Conservation Trade Act. 1990; Nyakatawa Reddy Sistani 1998; SAS Institute 1987

	ACKNOWLEDGMENTS

 
The authors acknowledge the financial assistance of the USDA/CSREES (Grant no. 96-38814-2845) in conducting the research reported herein.

Received for publication July 30, 1999.

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