ARS | Publication request: Cover Crop Use for Managing Broiler Litter Applied to Cotton in the Fall

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 5, 2010
Publication Date: January 1, 2011
Citation: Adeli, A., Tewolde, H., Jenkins, J.N., Rowe, D.E. 2011. Cover crop use for managing broiler litter applied to cotton in the fall. Agronomy Journal. 103:200-210.

Interpretive Summary: While spring application of manure provided the best agronomic response in most instances, animal manures are often applied to the soils in the fall possibly because of greater availability, lower cost, more time to apply, and weather risks of applying manure in the spring. 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 planting, particularly under conventional till systems. However, fall application of 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. Most of the N loss occurs as NO3-N leaching during the late fall and early spring months when the soil is under winter fallow. The capability of applying litter in the fall is vitally important to row crop growers and poultry producers in the Mid South and southeastern US. 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, any management practice that prevents or minimizes loss of broiler litter-derived N and enhances 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 objective of this study was to evaluate the effects of cover crop (winter rye vs. winter fallow) and broiler litter fertilization timing (fall vs. spring) on cotton growth, yield, and residual soil N.

Technical Abstract: Timing of broiler litter applications and cropping system have critical effect on both availability and leaching losses of N contained in broiler litter and should significantly influence cotton growth and yield. A 2-yr study was conducted in 2007 and 2008 on Leeper silty clay loam soil to evaluate the effect of broiler litter application timing and cover crop on cotton production. The experimental design was a randomized complete block design with a split-split plot treatment arrangement and four replications. 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 to both cover and no cover crop and incorporated immediately. In the absence of cover crop, spring-applied broiler litter had the best agronomic response and significantly increased number of bolls and lint yield by 15% and 21%, respectively (9 more boll m-2 and 314 kg more lint ha-1), compared to fall-applied litter. In addition, in the absence of cover crop residue, spring-applied broiler litter at a rate greater than 9 Mg ha-1 exceeded N need for optimum lint yield as evidenced by increasing NO3-N accumulation into the soil profile. Seeding a winter rye cover crop to fall-applied broiler litter did not significantly benefit cotton lint yield as compared to winter fallow, but provided environmental service to the agro-ecosystem by nutrient cycling and substantially reduced the potential of leaching loss of NO3-N.