Soybean Yield in Rotation with Corn and Cotton Is Boosted By Poultry Litter Fertilization.

The southern and southeastern US where soybean is grown in rotation with corn and cotton  produces the majority of broiler chickens and therefore generates enormous amounts of poultry litter. Soybean and other row crops can benefit from the availability of such a resource but how soybean responds to fertilization with poultry litter in rotation with corn and cotton is not well understood.  This research investigated soybean yield response to low rates (2.2 or 7.6 Mg/ha) of poultry litter fertilization on a Leeper silty clay loam soil in a corn (M)-cotton (C)-soybean (B) rotation system. The litter was applied as surface broadcast and incorporated before planting.  The rotation systems from 2010-2014 were CMBBM; CMCBM and CCMMB. The results showed annual rate of 2.2 or 7.6 Mg/ha poultry litter application increased soybean yield by >7% when rotated with cotton or corn but not when soybean followed soybean. The 7.6 Mg/ha litter increased yield by ≥11% relative to the no fertilizer check, but the yield difference between the 2.2 Mg/ha and 7.6 Mg/ha litter generally was only slight. In the no fertilizer check, the 2013 soybean that followed the 2012 soybean (CMBBM) had higher yield than the 2013 soybean that followed 2012 cotton (CMCBM). This difference was eliminated or reversed if 2.2 or 7.6 Mg/ha litter was applied, but annual application of 7.6 Mg/ha litter resulted in a slight build up of soil P, K, Cu, and Zn. The results overall suggest that applying as much as 7.6 Mg/ha litter may not be necessary to gain the full benefit of litter for soybean yield in this soil.  Only 2.2 Mg/ha litter may provide the yield benefits without causing excess nutrient build up in the soil.