Grain Yield Response to Poultry Litter Application Under a Wheat-Soybean Double Cropping System.

Poultry litter application and double cropping are management practices that could be used with conservation tillage systems to increase yields compared to conventional monocropping systems. The objective of this study was to evaluate wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.] yield response to poultry litter application compared to inorganic N fertilization under a double cropping system. The study was conducted from 2014 to 2016 at two locations on a Marvyn loamy sand (fine-loamy, kaolinitic, thermic Typic Kanhapludult) and a Lucedale fine sandy loam (fine-loamy, siliceous, subactive, thermic Rhodic Paleudult). At each location, the experimental design was a randomized complete block with six treatments replicated four times. Fertility treatments for winter wheat included an unfertilized control (P₀N₀), inorganic N fertilizer (135 kg ha^-1, P₀N₁₃₅), poultry litter at the rate of 45 kg N ha^-1 plus 90 kg ha^-1 inorganic N (P₄₅N₉₀), poultry litter at the rate of 90 kg N ha^-1 plus 45 kg ha^-1 inorganic N (P₉₀N₄₅), and poultry litter at the rate of 135 kg N ha^-1 (P₁₃₅N₀). All wheat treatments were double cropped with soybeans (no N fertilizer was added) and compared to a winter wheat fallow treatment. Poultry litter plus inorganic N significantly increased wheat yield at both locations compared to poultry litter application alone.  The P₉₀N₄₅ treatment resulted in the highest wheat yield compared to other poultry litter treatments, while no differences were observed when compared to the inorganic N only treatment (P₀N₁₃₅). Double cropping increased soybean yield for both locations, with soybean following wheat significantly increasing yield compared to the fallow treatment. This study suggests that a combination of poultry litter and inorganic N fertilizer use for a wheat-soybean cropping system could potential provide sustainable yield production.