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MANURE

No-Till and Conventional-Till Cotton Response to Broiler Litter Fertilization in an Upland Soil: Lint Yield

^a USDA-ARS, Mississippi State, MS 39762
^b Mississippi State Univ,. Pontotoc, MS 38863
^c USDA-ARS, Bowling Green, KY 42101
^d Mississippi State Univ., Mississippi State, MS 39762

^* Corresponding author (haile.tewolde{at}ars.usda.gov).

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
The effectiveness of poultry litter as cotton (Gossypium hirsutum L.) fertilizer is not well documented for upland soils in the southern and southeastern United States. The objective of this research was to measure cotton yield response to broiler litter fertilization in contrast to inorganic N fertilization and to quantify yield reduction due to lack of incorporation under no-till and conventional-till systems in an upland soil. Six treatments were tested in two unreplicated adjacent fields, one under no-till (NT) and the other under conventional-till (CT) management, from 2003 to 2006 near Pontotoc, MS. The treatments consisted of an unfertilized control (UTC), a standard fertilization (STD) with urea-ammonium nitrate solution (UAN), fertilization with 5.2 Mg ha^–1 incorporated or unincorporated broiler litter to supply 67% of the N need plus 34 kg ha^–1 UAN-N to supply 33% of the N need, and fertilization with 7.8 Mg ha^–1 incorporated or unincorporated broiler litter. Lint yield results showed broiler litter was a more effective cotton fertilizer than inorganic fertilizers under both NT and CT systems. The UTC produced an average across years of 870 kg ha^–1 lint under NT and 1105 kg ha^–1 under CT. The STD treatment increased yield over the UTC by only 121 kg ha^–1 (14%) under the NT and did not affect yield under the CT. Fertilization with litter-only when incorporated, relative to the UTC, increased lint yield by 260 kg ha^–1 (30%) under NT and by 137 kg ha^–1 (12%) under CT. The yield of this incorporated litter-only treatment exceeded the yield of the STD treatment by 139 kg ha^–1 (14%) under NT and by 115 kg ha^–1 (10%) under CT. Fertilization with litter also resulted in greater leaf area index but less chlorophyll index than the STD treatment. Lack of litter incorporation reduced yield by up to 84 kg ha^–1 under NT but did not affect yield under CT. Overall, broiler litter appears to be a more effective cotton fertilizer than conventional inorganic N fertilizers for this upland soil, but the inherent inability to incorporate under no-till may reduce this benefit.

Abbreviations: BL_i, incorporated litter • BL_ni, unincorporated litter • BL_i + UAN, incorporated litter plus UAN • BL_ni + UAN, unincorporated litter plus UAN • CT, conventional-till • LAI, leaf area index • NT, no-till • STD, standard fertilization • UAN, urea ammonium nitrate solution • UTC, unfertilized control

	NOTES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher.

Received for publication April 12, 2007.

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
POULTRY LITTER, which is generated in abundance in the southern and southeastern United States, is a rich source of nearly all mineral nutrients needed for cotton growth (Tewolde et al., 2005a, 2005b). It has been shown to be an effective fertilizer for forage and pasture crops (Evers, 1998), row crops (Tewolde et al., 2007), and forest trees (Samuelson et al., 1999), but it has been used most extensively as a fertilizer on forage and pasture crops on farms near poultry houses. Litter has seen limited use as a fertilizer for row crops which constitute a large fraction of the cultivated land in the southern and southeastern United States.

Cotton is one of the most dominant and important field crops in the same southern and southeastern states that also produce much of U.S. poultry. In Mississippi, it is grown largely on alluvial floodplain soils in the Mississippi delta region, but a significant fraction is also grown on the upland soils of northern Mississippi which tend to be low in organic matter and pH, high in silt and sand content, and are highly erodible. No-tillage, along with other soil conservation practices such as winter cover crops, has been recommended to maintain crop productivity in these soils (Boquet et al., 2004; Meyer et al., 1999). As a result, NT cotton production has steadily increased over the years. In the delta of Mississippi, as much as 38% of the cotton is produced using NT management practices (Martin and Cooke, 2004).

Use of poultry litter to fertilize NT cotton implies surface application without incorporation which exposes the litter and its nutrients to risks of loss in runoff water, volatilization, and wind erosion. Volatilization loss of NH₃–N from litter applied in the summer has been reported to exceed 24% with the greatest loss occurring in the first week of application (Sharpe et al., 2004). Runoff from NT systems in loessial soils can be substantially greater than runoff from CT systems (Dabney et al., 2004), which suggests loss of litter-derived nutrients to runoff may also be greater under NT than under CT. The reduction in litter benefit due to lack of incorporation in NT systems is not well researched. Furthermore, the effectiveness of surface-applied unincorporated litter under NT or reduced-till cotton production systems in the upland soils of the southern and southeastern United States relative to conventional inorganic fertilizers is not well documented. Therefore, the objectives of this research were to determine the effectiveness of broiler litter as a fertilizer for cotton relative to conventional inorganic N fertilizers and to quantify any yield reduction in the absence of incorporation under NT and CT systems in an upland soil.

	MATERIALS AND METHODS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
The research was conducted from 2003 to 2006 at the Mississippi Agricultural and Forest Experiment Station near Pontotoc, MS (34°8'30'' N, 88°59'36'' W, 165 m alt.) in an Atwood silt loam soil (fine-silty, mixed, semiactive, thermic Typic Paleudalfs). In 2003 to 2005, six treatments of an unfertilized control, a fertilized standard, litter-only, and litter plus inorganic N as UAN were tested in two unreplicated adjacent fields, one under NT and the other under CT. The soil pH about 1 mo before planting in 2003 ranged between 5.95 and 6.39 under the NT and between 6.36 and 6.80 under the CT. The entire NT field received about 560 kg ha^–1 lime (CaCO₃) about 2 wk before planting in 2003 to increase the soil pH to approximate that of the CT field. The treatments under each tillage included an UTC, a standard fertilization that received UAN–N plus inorganic P and K if recommended based on soil test (STD), incorporated broiler litter to supply 67% of the N requirement plus UAN to supply 33% of the N requirement, unincorporated broiler litter to supply 67% of the N need plus UAN to supply 33% of the N requirement, incorporated broiler litter to supply 100% of the N need, and unincorporated broiler litter to supply 100% of the N requirement. The incorporated treatment under NT was included to measure yield reduction due to the inherent lack of incorporation. This treatment will be referred to as the incorporated treatment under NT for purposes of comparison in discussing the results although, under typical production practices, it may also be referred to as minimal till depending on the magnitude of incorporation and residue turnover.

Litter rate to deliver target N amount was determined assuming 50% of the total litter N becomes plant available for plant uptake within the cotton growing season (Tewolde et al., 2007). Litter alone, UAN, or a combination of litter and UAN were applied to supply 101 kg ha^–1 plant available N based on general N recommendations for Mississippi (McCarty, 2006) for a target yield of approximately 1000 to 1100 kg ha^–1 lint which is a reasonable expectation for this soil. Based on this target fertilization, the STD treatment under both the NT and CT received 101 kg ha^–1 UAN–N each of the 3 yr. This treatment under the NT also received 20 kg P ha^–1 as triple superphosphate each of the 3 yr and 37 kg K ha^–1 as KCl in 2003 based on soil test and recommendation by the Soil Test Laboratory of Mississippi State University. The STD treatment under the CT received no P fertilization in any of the 3 yr but received 37 kg K ha^–1 as KCl in 2003 based on the recommendation. The litter-only treatments received 8.2 Mg ha^–1 litter in 2003 and 7.6 Mg ha^–1 in 2004 and 2005 based on pre-application N analysis of the litter. The litter plus UAN treatments received 5.5 Mg ha^–1 litter plus 34 kg ha^–1 UAN–N in 2003 and 5.1 Mg ha^–1 litter plus 101 kg ha^–1 UAN–N in 2004 and 34 kg ha^–1 UAN–N in 2005. The litter plus UAN treatments in 2004 received 5.1 Mg ha^–1 litter plus, inadvertently, 101 kg ha^–1 UAN–N instead of the planned 34 kg ha^–1 UAN–N. With this exception, a plot received the same treatment each of the 3 yr under each tillage. Only the STD treatment was fertilized in 2006 as the purpose in this year was to quantify the magnitude of residual effect of litter applied during the previous 3 yr.

The litter in 2003 and 2004 was surface-applied before planting on 29 Apr. 2003 and on19 May 2004 with a small-plot spreader with approximately 150 kg litter-holding capacity. The spreader was equipped with a system that controlled application rate and dispensed the litter evenly across a 1.8-m swath. The litter was ground immediately before application to pass a 12-mm screen to facilitate uniform flow. Because of mechanical failure with the spreader, litter in 2005 was spread by hand on 5 May 2005. Once applied by either method, the litter for the NT incorporated treatment was lightly incorporated into the top approximately 0.05 m soil using a tractor-powered rotary tiller within 4 h after application. Litter for the CT incorporated treatments was applied after disking but before hipping (bedding) which served as the method of incorporation. The litter which was obtained from a nearby broiler chicken producer was not composted. Litter moisture and nutrient concentrations are shown in Table 1 .

The six treatments were tested under a randomized complete block design replicated four times within each tillage. Each plot consisted of six 13.7 m-long rows spaced 1.01 m apart. The CT field was prepared each year by disking once before planting, running a do-all (an implement consisting of a furrow opener, a rolling chopper, and a spiked-tooth harrow) to break clods and condition the beds, applying the litter to the incorporated treatments, and hipping the entire field immediately. Both the NT and CT fields were planted with wheat (Triticum aestivum L.) cover crop each fall. Cotton cv. DPL 451 BR was planted in the Spring on 27 May 2003, 20 May 2004, 6 May 2005, and 19 May 2006 after killing the cover crop and any winter weeds with glyphosate [N-(phosphonomethyl) glycine] approximately 15 d before planting. Weeds and insect pests were managed using conventional, recommended pesticides.

The cotton was defoliated on 18 Oct 2003, 30 Sept. 2004, 30 Sept. 2005, 15 Sept. 2006 and harvested on 5 Nov. 2003, 10 Nov. 2004, 11 Oct. 2005, and 24 Oct. 2006. In 2003, two middle rows in a plot were picked with a one-row picker that was retrofitted with a self-weighing basket. Four middle rows were picked in 2004, 2005, and 2006 with a two-row picker which was also retrofitted with a self-weighing basket. Lint turnout from each plot was determined from about 1.0 kg grab samples taken at the time of harvest. The samples were weighed before and after air-drying to constant moisture in paper bags and ginned on a 10-saw bench-top gin. Lint turnout, calculated as 100 x lint weight/(weight of lint+seed+trash), was used to convert the seed cotton yield to lint yield which was adjusted for moisture. Subsamples from the ginned samples were used to measure fiber quality including fiber length, strength, micronaire, elongation, and length uniformity using high volume instrumentation (StarLab Inc., Knoxville, TN).

In addition to lint yield and fiber quality, leaf area index (LAI) and leaf chlorophyll index were measured three times each season between early flowering and early boll opening stages. Leaf area index was determined based on visible light (400–700 nm) interception by the canopy of a pair of rows in the middle rows of each plot with AccuPAR model PAR-80 (Decagon Devices, Pullman, WA) following guidelines suggested by Tewolde et al. (2005c). Leaf chlorophyll index was measured using Minolta's hand-held SPAD-502 meter (Minolta Corp., Ramsey, NJ) on the youngest most mature main stem leaves.

Daily maximum and minimum air temperature and rainfall were recorded at a National Weather Service's Cooperative Station Network located at the experiment station and downloaded from the National Climatic Data Center (NCDC, 2006).

Treatment effects were tested by subjecting all data to statistical analysis using mixed model analysis on SAS (Littell et al., 2002). Data from 2003 to 2005 of both tillages were analyzed to test for interactions between year or tillage with treatments. Treatment means were compared by LSD or using single degree of freedom contrasts where well-defined structures existed.

	RESULTS AND DISCUSSION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
The 2003, 2004, and 2005 growing seasons were similar in air temperature and total rainfall. Total rainfall received during the critical part of the season in June, July, and August was 455, 434, and 430 mm in 2003, 2004, and 2005 respectively. The cotton suffered occasional but no extended drought in each of the three seasons. Maximum air temperature averaged across June, July, and August was 29.6, 29.0, and 30.9°C in 2003, 2004, and 2005, respectively, with corresponding average minimum air temperature of 19.8, 19.2, and 20.8°C. The 2006 season, however, was much different than the previous 3 yr. Only 132 mm of total rain fell during June, July, and August in 2006 in sharp contrast to the >400 mm rain received during these 3 mo in 2003 to 2005. Maximum air temperature averaged across these 3 mo in 2006 was 33.4°C which is 2 to 3°C greater than the average maximum temperature in the other 3 yr. The crop therefore was subjected to greater drought and temperature stress in 2006 than in the other 3 yr. Among all four seasons, the 2004 season appeared to be the most favorable growing season, but a hail storm on 13 Sept. 2004 caused defoliation so severe that lint yield in 2004 was <50% that of 2003. Therefore, data collected after the hail storm in 2004 will not be presented.

Litter versus Inorganic Nitrogen Fertilization
Lint yield results demonstrated broiler litter is an effective cotton fertilizer in this soil regardless of the tillage. Fertilizing with litter alone outperformed fertilizing with conventional inorganic fertilizers or with a combination of litter and inorganic fertilizers. When pooled across 2003 and 2005, as there was no treatment by year interaction (Table 2 ), the litter-only treatment under the NT increased lint yield over the UTC by 260 kg ha^–1 (29.9%) when it was soil incorporated and by 176 kg ha^–1 (20.2%) when it was not incorporated (Table 3 ). The litter plus UAN–N treatment under this tillage also increased lint yield over the UTC by 183 kg ha^–1 (21%) when the litter was soil-incorporated and by 144 kg ha^–1 (16.6%) when it was not soil-incorporated. Our results are similar to those of Endale et al. (2002) who reported NT cotton yield was better when fertilized with poultry litter than with conventional inorganic fertilizers although the differences were not always significant. Unlike our results and those of Endale et al. (2002), Nyakatawa et al. (2000) reported no lint yield increase when the cotton was fertilized with litter that supplied equivalent plant available N as ammonium nitrate. Nyakatawa et al. (2000) were able to improve yield only when they applied litter to supply plant available N twice that of ammonium nitrate.

Litter was also effective in increasing lint yield under the CT but was less effective under CT than under the NT. Relative to the UTC, the litter-only treatment under the CT increased lint yield by 137 kg ha^–1 (12.4%) when soil-incorporated and by 147 kg ha^–1 (13.3%) when not-incorporated (Table 3). Under this tillage, the STD treatment did not improve lint yield compared to the UTC. While the lack of significant yield increase by the STD treatment may be because of the greater lint yield of the UTC under the CT than under the NT, the results suggest nutrients other than the applied nutrients to the STD treatment and other soil conditions limited lint production under both NT and CT. Litter may have at least partly eased these unidentified nutrient deficiencies or improved the unknown detrimental soil conditions. Soil analysis at the end of the 2005 season showed that litter application increased soil total carbon, Cu, and Zn concentrations. It also elevated soil concentrations of total N and Mehlich 3 extractable (Mehlich, 1984) P and K. At the end of the 2005 season under the CT, the litter-only treatment (averaged across the incorporated and nonincorporated treatments) had 9.4 g kg^–1 total C, 0.87 g kg^–1 total N, 83 mg kg^–1 P, and 0.22 g kg^–1 K in the top 0.15 m soil profile compared with 7.4 g kg^–1 total C, 0.67 g kg^–1 total N, 45 mg kg^–1 P, and 0.17 g kg^–1 K for the STD. The corresponding soil nutrient concentrations under the NT were 9.2 g kg^–1 total C, 1.2 g kg^–1 total N, 31 mg kg^–1 P, and 0.28 g kg^–1 K for the litter-only treatments compared with 8.4 g kg^–1 total C, 0.9 g kg^–1 total N, 16 mg kg^–1 P, and 0.22 g kg^–1 K for the STD. However, it is not clear from this research which of these nutrients contributed to the better performance of the litter treatments. The soil in this area is characterized by marginal organic matter content, high silt and sand content, and low productivity relative to soils in the delta of Mississippi. A previous finding showed fertilizing CT cotton with a combination of litter and inorganic N in a Mississippi Delta soil did not show the same yield benefits as found in this upland soil (Tewolde et al., 2007). But the same combination of litter and inorganic N applied to NT cotton on this nondelta soil increased yield beyond that fertilized with conventional inorganic fertilizers.

Lint turnout, which is the weight of lint relative to harvested seed cotton, showed expected response to inorganic N fertilization but somewhat unexpected response to litter fertilization. Lint turnout decreased from 38.6% for the UTC to 37.0% for the STD under the NT and from 38.5% for the UTC to 36.7% for the STD treatment under the CT (Table 3). This is an expected and well-known response to N. Nitrogen deficiency is known to increase lint turnout relative to well-fertilized cotton because N deficiency, apparently, affects seed growth more than lint growth. Adequate supply of inorganic N supply, on the other hand, increases seed growth more than it increases lint growth and therefore the lint to seed cotton weight ratio is greater when plants are N deficient than N sufficient. However, this did not appear to be the case when plants were supplied with adequate amount of N from broiler litter based on lint yield. Lint turnout of the litter-only treatments under both tillage systems was more similar to that of the UTC than to the STD treatment. Lint turnout of the litter-only treatments averaged across the incorporation treatments was 38.4% under the NT and 37.9% under the CT which was significantly greater than the turnout of the STD treatment under the respective tillage (37.0 under NT and 36.7% under CT) but similar to the turnout of the UTC (38.6% under NT, 38.5% under CT). Treatments that received a combination of litter and UAN–N had lint turnout essentially the same as the STD treatment. The basis for the difference between the STD and litter fertilized treatments in lint turnout is not obvious from this research but could be related to differences in the availability and uptake rate of N. The availability and uptake rate of N at the time of boll growth was probably greater in the STD treatment than in the litter fertilized treatments. All of the litter N is not plant available at any given time; it mineralizes and becomes plant available gradually throughout the season.

Among the fiber quality measurements, differences between the STD and the litter-only treatments existed only in fiber length and elongation (Table 3). The litter-only treatments resulted in slightly longer fibers under both CT and NT but had less elongation than the STD treatment under the CT. Compared with the STD treatment, litter did not affect the other fiber properties.

Interestingly, measurement of chlorophyll index revealed that plants that received the STD treatment were distinctly greener than plants that did not receive UAN which suggests the poor yield performance of the STD treatment relative to the litter treatments was not due to inadequate N. The STD treatment, which received all of its N fertilization as UAN, had greater chlorophyll index than the litter-only treatments in almost all the measurements under both tillage systems, but the differences were significant usually in the last two measurements each year (Table 4 ). These results show that fertilizing with UAN results in greener foliage than fertilizing with litter alone regardless of whether lint yield was increased. Visually, this effect was distinct as it was easy to identify plots that received the STD treatment based on leaf color intensity.

The effect of litter incorporation under the NT was also apparent in 2006 when no litter was applied. The overall yield in 2006, relative to the other years, was low mainly because of an extreme dry season with only 146 mm of rain during the entire growing season compared with >550 mm in each of the other 3 yr. But the results show the nonincorporated litter applied in the previous 3 yr resulted in lint yield reduction although this reduction was not statistically significant. Lint yield decreased by 16.9% from 391 to 325 kg ha^–1 due to lack of litter incorporation in the litter-only treatments and by 9.2% from 370 to 336 kg ha^–1 in the litter plus UAN treatments (Table 6 ). The coefficient of variation of 23% suggests the lack of significant difference between incorporated and nonincorporated treatments may be because of large experimental variation. The difference between incorporated and nonincorporated litter in 2006 was even better reflected in chlorophyll index measurements. Soil incorporation of litter significantly increased chlorophyll index in both the litter-only and litter plus UAN treatments under the NT (Table 6). Because chlorophyll index measured with meters such as the SPAD usually indicates the N nutrition level, these results suggest that incorporating litter applied in the previous 3 yr has helped conserve residual N, most likely organic N. The difference between litter incorporation and nonincorporation in 2006 was detected with LAI measurements less effectively than with chlorophyll index measurements (Table 6).

Chlorophyll index and LAI under the CT in 2006 did not respond to litter incorporation in the previous 3 yr probably because unincorporated litter applied to the freshly cultivated soil may have gradually moved through cracks and crevices into the soil throughout the season. This may not have prevented loss of volatile compounds from freshly applied litter but may have protected the organic N fraction from being lost after gradual mineralization as would be expected under the NT where the litter remains exposed on the surface throughout the year. Organic N is the fraction that carries over to successive seasons.

	CONCLUSIONS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Results of this research showed broiler litter is a more effective cotton fertilizer than conventional inorganic fertilizers in this soil type regardless of whether the cotton was grown on tilled or untilled soil. This effectiveness most likely is because litter is a rich source of nearly all essential mineral nutrients and may have corrected, in part or in full, unidentified nutrient deficiencies or improved unknown detrimental soil conditions in addition to supplying the nutrients N, P, and K. The results also showed lack of litter incorporation leads to a reduction of the fertilizer value of the litter under NT, but the reduction may be small (about 8% yield reduction). Lack of incorporation may not affect fertilizer value when the litter is applied to a freshly tilled soil under CT systems as litter may move down through open spaces of a freshly tilled soil.

	ACKNOWLEDGMENTS

 
We would like to thank Richard Switzer and Steve Stokes of USDA-ARS and Trevor Garrett and Jeff Main of Mississippi State Univ. for providing technical assistance in this research.

All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher.

	REFERENCES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 

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