Cover Crop Use for Managing Broiler Litter

The use of broiler litter as a source of plant nutrients for row crops is becoming more common.  The timing of manure application may affect soil nitrogen content, crop nitrogen use efficiency and crop performance. For example, the spring application of manure to corn provides the best agronomic response in most cases and manure N use efficiency increases with spring application compared with fall application.

While spring application of manure provided the best agronomic response in most instances, manures are often applied to the soils in the fall, possibly because of greater availability, lower cost, more time to apply and busy spring planting schedules for farmers. In addition, weather risks of applying manure in the spring which allows small windows of opportunity for planting and is less favorable for land preparation.

In Mississippi, due to wet winter months and in most cases early spring, row crop farmers are forced to apply broiler litter in the fall to prevent delayed manure over a winter fallow is risky because considerable amount of the litter N can be lost to leaching rendering the litter less effective for spring-planted crops. Fall litter application is also associated with potential environmental contamination. Loss of N derived from litter occurs both as leaching and denitrification of NO3–N.

The capability of applying litter in the fall is vitally important to row crop growers and poultry producers in the Mid-South and southeastern United States. Many apply broiler litter in the fall as a source of P and K, and then apply a full N rate from inorganic sources in the spring. This practice can lead to nutrient accumulation in the soil and adversely impact the environment. Therefore, management practices that prevent or minimize loss of broiler litter-derived N and enhance the cycling of N applied during the off-season for use by subsequent summer crops offers great practical benefit to growers.
Cover crops have been promoted as a means of maximizing the efficient use of available N to subsequent crops in agricultural systems, potentially enhancing profitability through reduced inorganic fertilizer N requirement.

The use of winter cover crops to capture inorganic N and to reduce leaching losses by recycling NO3–N, especially in areas that have high levels of winter and spring precipitation, is receiving renewed attention. During one 3-yr study, NO3–N leaching losses under the winter-fallow treatment averaged 20 kg N ha−1 yr−1 compared with 1.2 kg N ha−1 yr−1 under the winter cover cropped treatment, when using an ammonium nitrate fertilizer for the preceding corn.

Winter rye cover crops have been shown to increase the efficient use of available N to subsequent crops in the spring, resulting in reduced NO3–N leaching loss while potentially enhancing profitability through reduced inorganic fertilizer N requirements. The scavenging ability of cover crops, particularly rye, to sequester and reducing N leaching loss has been documented.

However, the effect of cover crop followed with fall-applied broiler litter on NO3–N sequestration has not been documented. These researchers hypothesized that seeding of a cover crop, such as winter rye, following fall applied broiler litter could be effective practice in reducing leaching losses of litter-derived N during fall, winter, or early spring. The objective of their research was to evaluate the effects of cover crop (winter rye vs. winter fallow) along with broiler litter fertilization timing (fall vs. spring) on cotton, yield, leaching loss, and residual soil NO3–N.


A field study was conducted in 2007 and 2008 on Leeper silty clay loam soil to evaluate the impacts of a winter rye cover crop and broiler litter timing on cotton yield, yield components, and leaching loss of NO3–N. Broiler litter was applied to the soil at the rates of 0, 4.5, 9, and 13.4 Mg ha−1 in the fall and spring for both cover and no cover crop and incorporated immediately. Winter rye cover crop was planted following broiler litter application in the fall.

The researchers found that averaged across cropping system and broiler litter timing, cotton lint yield and yield components increased with increasing broiler litter application. Application of broiler litter at a rate >9 Mg ha−1 was not advantageous and exceeded N need for optimum lint yield as evidenced by increasing postharvest NO3–N in the soil profile.

In the absence of cover crop and averaged across litter rates, spring-applied broiler litter had the best agronomic response and increased lint yield by 19 and 18% compared with fall-applied litter in 2007 and 2008, respectively. Seeding a winter rye cover crop to fall-applied broiler litter did not benefit cotton lint yield and yield components but substantially reduced leaching loss of NO3–N.


Summary adapted from:

Cover Crop Use for Managing Broiler Litter Applied in the Fall
A. Adeli,* H. Tewolde, J. N. Jenkins, and D.E. Rowe
Published in Agron. J. 103:200–210 (2011)
Published online 6 Dec. 2010
Abstract


Photo USDA NRCS: Contour farming, terraces and rye grass field strips. Tifton, GA.