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© 2004 Plant Management Network.
Accepted for publication 9 December 2003. Published 16 January 2004.

An Investigation of Poultry Litter as a Nitrogen Source for Wheat

Robert A. Clark, Extension Agent, Agriculture and Natural Resources, Crop and Soil Sciences, Virginia Cooperative Extension, Shenandoah County, Woodstock 22664; and Greg L. Mullins, Extension Specialist, Department of Crop and Soil Environmental Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061

Corresponding author: Robert A. Clark. raclark@vt.edu

Clark, R. A., and Mullins, G. L. 2004. An investigation of poultry litter as a nitrogen source for wheat. Online. Crop Management doi:10.1094/CM-2004-0116-01-RS.

Abstract

Many farmers have been reluctant to use poultry litter as a nutrient source for wheat due to fears of excessive lodging and uncertainty regarding yield response. This three-year research project investigated yield response and lodging caused by applying raw broiler litter, granulated poultry litter, pelleted poultry litter, and commercial fertilizer nitrogen (N) to wheat (Triticum aestivum) at Zadoks growth stage (G.S.) 25 and 30. Results from this research project indicate that in two out of three years both raw broiler litter and commercial fertilizer N resulted in a significant yield response to N additions, and the raw broiler litter additions resulted in yields equivalent to what was obtained using commercial fertilizer N. There were no differences in yield or lodging between poultry litter applications made at G.S. 25 or 30. Granulated poultry litter resulted in equivalent yields to what was obtained using commercial N fertilizer in one out of two years. The raw broiler litter, granulated poultry litter, and pelleted poultry litter caused no more lodging than the commercial fertilizer N.

Introduction

Farmers in the Shenandoah Valley region of Virginia annually grow an average of 4,275 and 4,575 acres of wheat (Triticum aestivum) and barley (Hordeum vulgare) for grain, respectively (8,9). Within this region, there is an abundant supply of poultry litter and poultry litter has been proven to be a good source of nutrients. Nutrient management standards in Virginia recommend using an organic nitrogen (N) availability coefficient of 30% for winter topdress poultry manure (10). However, many farmers are reluctant to use poultry litter on wheat or barley due to fears of excessive lodging and uncertainty regarding yield response. Alley et al. (1) indicate that excessive plant-available N can produce wheat plants that are susceptible to lodging. Furthermore, many fertility experts have been reluctant to recommend a winter topdress of poultry litter due to concerns that the litter N would not mineralize quick enough to supply enough N for growing small grain.

There are several reasons farmers should consider using poultry litter as a nutrient source for small grain production. In many instances, fertilizing wheat or barley with litter is less expensive than fertilizing with commercial fertilizer. Secondly, current nutrient management standards allow litter to be applied to small grain later in the fall and earlier in the spring than what is recommended for most other crops (11). This increases the window of opportunity when farmers can land-apply litter. The third benefit is related to the marketability of poultry litter. Assuming that on average an acre of small grain requires 80 lb of N and removes 35 lb of P₂O₅, then, given the present acreage of small grains produced in this region, growers could utilize the N from 17,000 tons of poultry litter or remove all of the P₂O₅ supplied by 6,000 tons of poultry litter. There is additional acreage of small grain managed for silage that could also benefit from poultry litter.

The objective of this study was to evaluate the effectiveness of poultry litter as a N source for small grain when applied at G.S. 25 and 30. A secondary objective was to evaluate the yield response of wheat to commercial fertilizer N applications at G.S. 25 and 30.

Experiments on Poultry Litter Applications to Wheat

Wheat plots were established during the 1997-1998, 1999-2000, and 2000-2001 growing seasons. The 1997-1998 plots were located at 38°38’33.88”N, 78°41’0.27”W and the other two plots were within three miles of this area. The 1997-1998 and 1999-2000 plots were planted on a Frederick silt loam (Clayey, mixed, mesic Typic Hapudults), and the 2000-2001 plots were planted on a Wolfgap loam (Fine-loamy, siliceous, mesic Fluventic Hapludolls). Soil samples were collected from the plot areas each year just prior to planting and analyzed by the Virginia Tech soil-testing laboratory. Lime, phosphorus, and potassium were applied according to soil test recommendations. Each year, 25 lb of N per acre in the form of ammonium nitrate were applied pre-plant uniformly over the entire plot area. All fertilizer and lime were incorporated prior to planting. The plots were planted with a Hege plot drill at a rate of about 22 seeds per foot. This drill plants seven rows on seven-inch spacing. During the winter the plots were trimmed to nine feet in length. The variety of wheat planted was Jackson in 1997-1998 and 1999-2000 and Pioneer 26R24 in 2000-2001. Harvesting was done with a Massey Ferguson 8XP plot combine equipped with a HarvestMaster system (HarvestMaster, Ogden, UT).

Each winter litter was collected directly from a broiler house, mixed, sampled, and stored in black garbage bags. The litter was analyzed by the Maryland Cooperative Extension Soil Testing Laboratory (5). The granulated poultry litter (used in 1999-2000 and 2000-2001) and the pelleted poultry litter (used in 2000-2001) were obtained from Harmony Products Inc. and Virginia Dehydrating Inc., respectively. The nutrient analysis of these two products was obtained from the manufacturers. The analysis of the various poultry litter sources used in this experiment are shown in Table 1.

Table 1. Analysis of products used in test sites.*

* Percentages on a wet basis.

Tiller counts per foot of row were made randomly over the entire plot area at Zadoks G.S. 25. Each year, the rate of N was adjusted to account for differences in growth based on visual observations, tiller counts, and tissue samples based on the recommendations of Alley et al. (1). Tables 2 and 3 contain treatment information for 1997-1998 and 2000-2001. All treatments were replicated four times and arranged in a randomized complete block design. All treatments were hand applied at either G.S. 25 or 30. The rate of litter applied to each plot was adjusted to supply the desired amount of plant-available nitrogen (PAN) based on the equation (PAN = 0.5 × (NH₄-N) + 0.6 × (organic N)). The rate of granulated and pelleted poultry litter applied to each plot was based on the assumption that 55% of the total N would become plant-available. The commercial fertilizer N treatment consisted of a mixture of ammonium sulfate and ammonium nitrate such that the N:S ratio was the same as what is commonly present in broiler litter.

Table 2. Data from the 1997-1998 plots.

* The broiler litter rates are estimated rates of plant-available nitrogen (PAN) based on the equation (PAN = 0.5 × (NH₄-N) + 0.6 × (organic N)).

** BL = raw broiler litter and F = commercial fertilizer N.

Table 3. Description of treatments in 2000-2001.

* The broiler litter rates are estimated rates of plant-available nitrogen (PAN) based on the equation (PAN = 0.5 × (NH₄-N) + 0.6 × (organic N)). The rates of granulated and pelleted poultry litter are estimated rates of PAN based on the assumption that 55% of the total N would become plant-available.

** F = commercial fertilizer N, BL = raw broiler litter, GPL = granulated poultry litter, and PPL = pelleted poultry litter.

The plots were evaluated for lodging immediately prior to harvest using the Belgian lodging rating system. The Belgian Lodging Scale equals Area × Intensity × 0.2. Area is on a scale of one to ten, where unaffected wheat is assigned a value of one and a value of ten is assigned if the entire plot is affected. Intensity is on a scale one to five where wheat standing upright is assigned a value of one and value of five is assigned if the wheat is totally flat (7).

All data were analyzed by analysis of variance using Statistical Analysis System Institute software (6). Mean separation was performed using Fisher's protected LSD and a priori significance level of P < 0.10.

Summary of 1997-1998 Data

The addition of poultry litter or commercial N at either G.S. 25 or 30 resulted in a positive wheat yield response when compared to treatments where no additional N was applied (Table 2). There were no yield differences between litter applied at G.S. 25 or 30. It is noteworthy that the entire plot area averaged 102 tillers per square foot at G.S. 25. Alley et al. (1) do not recommend that additional N be applied at G.S. 25 when tiller counts at G.S. 25 exceed 100 tillers per square foot.

The yields for the commercial fertilizer N treatments were slightly higher than the litter N treatments at the same N application rates. Crouse (2) suggested that the rate of N mineralization from litter applied to small grain is much lower than the prediction equation normally used in North Carolina. The North Carolina Department of Agriculture uses a prediction equation that assumes 45% of the total N in broiler litter will become plant-available during the first crop year after application. Hadas et al. (4) and Gale and Gilmour (3) noted that net N mineralization increases with increasing soil temperatures.

There was a tremendous amount of lodging in the Shenandoah Valley during the 1997-1998 growing season. The severity of lodging in these plots increased with increasing rates of N regardless of source. All of the commercial N treatments showed higher lodging ratings as compared to equivalent litter treatments. There are two possible reasons why this might have occurred. First, the litter contained additional nutrients not contained in the commercial N sources (potassium, phosphorus, magnesium, etc.). This may have improved stalk strength. Secondly, the actual amount of N available from the litter to the crop may have been slightly less than what was predicted by the availability equation.

Summary of 1999-2000 Data

There were no yield responses to any of the treatments in 1999-2000 (data not shown). First, the previous corn crop was poor due to a lack of rainfall. Thus, the previous corn crop probably did not utilize all of the N that had been applied. Secondly, a pre-plant application of N at 25 lb/acre was made uniformly across the entire plot area. These two factors probably provided most of the N needed for the entire crop. Finally, the wheat was planted late (October 25) and growing conditions did not result in high yields. Average yield for the entire plot area was 70 bu/acre and yields for the adjoining state wheat variety test plots averaged 72 bu/acre. There was virtually no lodging at harvest.

Summary of 2000-2001 Data

Table 3 contains a summary of the treatments used in the 2000-2001 plots. Yields were not affected by the time of application (Table 4) or by the interaction of time of application with either source or rate of N. This was a surprise because the wheat stand was poor at G.S. 25. There were significant yield responses to the addition of N compared to treatments where no additional N was added to the wheat (Table 5). It is somewhat surprising that the check plot (no additional N treatment) had an average yield of 90 bu/acre. However, the entire plot area had received N at 25 lb/acre prior to planting. In addition, the soils in the plot area are extremely deep and loamy which may have supplied a large amount of residual N.

Table 4. Effects of time of application on wheat yield, lodging, and test weights in 2000-2001. Means do not include the check treatment.

Table 5. Wheat yield data from the 2000-2001 test.

* The broiler litter rates are estimated rates of PAN based on the equation (PAN = 0.5 × (NH₄-N) + 0.6 × (organic N)). The rates of granulated and pelleted poultry litter are estimated rates of PAN based on the assumption that 55 percent of the total N would become plant-available.

Lodging was affected by the rate of N application and by N source (Table 6) but not by timing of application. The N in the raw broiler litter and pelleted litter treatments likely mineralized slower than predicted. There were no significant differences between treatments for test weight.

Table 6. Effects of nitrogen source on wheat yield, lodging, and test weights in 2000-2001. Means do not include the check treatment.

There was likely a yield × lodging interaction that affected the outcome of this data.

Conclusions

The primary objective of this research project was to determine if poultry litter could be used as a N source for wheat when applied in late winter/early spring. A secondary objective was to evaluate wheat yield response to late winter/early spring N applications. In all cases, raw broiler litter resulted in equivalent yields to what was obtained using commercial fertilizer N. Also, the raw broiler litter caused no more lodging than the commercial N.

One question that may arise is whether or not it is better to apply litter at G.S. 25 or 30. The data from this project indicated that there were no differences in yield response to applying litter at G.S. 25 when compared to G.S. 30. From a practical standpoint, this means that in years when there is a good stand of wheat at G.S. 25, delaying the litter application until G.S. 30 (for example, when the field is too wet) will likely not hurt yield. However, due to such factors as the bulky nature of litter, truck weight, and slow winter N mineralization rate, most farmers will want to apply the litter as soon as the weather permits in late winter/early spring.

There was a significant yield response from commercial N fertilizer applications in two out of the three years of this test. In both years, when a yield response occurred, the optimum rate for N was somewhere between 40 and 80 lb N per acre. However in this study, yield responses from the addition of nitrogen were generally small ranging from 5 to 15 bu/acre.

Acknowledgments

The authors would like to express their appreciation to the following individuals for contributing to this work: Dr. Dann Brann, Harry Beahl, Dr. Ozzie Abaye, Elizabeth Rucker, and Tom Stanley.

Literature Cited

1. Alley, M. M., Scharf, P., Brann, D. E., Bathgen, W. E., and Hammons, J. L. 1996. Nitrogen management for winter wheat: Principles and recommendations. Virginia Coop. Ext. Pub. No. 424-026.

2. Crouse, D. A. 1993. Poultry litter as a N source for winter wheat: A field evaluation of the plant-available N coefficients. M.S. Theses. North Carolina State Univ., Raleigh, NC.

3. Gale, P. M., and Gilmour, J. T. 1986. Carbon and nitrogen mineralization kinetics for poultry litter. J. Environ. Qual. 15:423-426.

4. Hadas, A., Bar-Yosef, B. Davidov, S., and Sofer, M. 1983. Effect of pelleting, temperature, and soil type on mineral nitrogen release from poultry and dairy manures. Soil Sci. Soc. Am. J. 47:1129-1133.

5. Maryland Cooperative Extension. 2001. Maryland Coop. Ext. Soil Test. Lab. College Park, MD.

6. SAS. 1985. SAS for Linear Models: A Guide to the ANOVA and GLM Procedures. Statist. Analysis Sys. Inst. Cary, NC.

7. Szoke, T. G., Anthonissen, J., and Vergracht, J. 1979. New ethephon based anti-lodging product for barley. Pages 843-852 in: Proc. Int. Symposium on Crop Protection. Ghent, Belgium. Faculteit Landbouwwetenschappen, Ghent, Belgium.

8. Virginia Agricultural Statistics Service, 1999. Virginia agricultural statistics bulletin and resource directory. Virginia Dept. Agric. Consumer Serv., Richmond, VA.

9. Virginia Agricultural Statistics Service, 2001. Virginia agricultural statistics bulletin and resource directory. Virginia Dept. Agric. Consumer Serv., Richmond, VA.

10. Virginia Department of Conservation and Recreation, 1995. Virginia nutrient management standards and criteria. Richmond, VA.

11. Virginia Department of Conservation and Recreation, 2002. Nutrient management plan special conditions for Virginia pollution abatement (VPA) permits. Richmond, VA.