Double-Crop Wheat and Soybean Yield Response to Poultry Litter Application

Poultry litter (PL) application and double cropping are management practices that could be used with conservation tillage to increase yields compared with conventional mono-cropping systems. The objective of this study was to evaluate winter wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.] yield response to PL alone and combinations of PL and inorganic N versus inorganic N alone when applied to the winter wheat in a double-cropping system. The study was conducted from 2014 to 2016 at two locations on a Marvyn loamy sand and a Lucedale fine sandy loam. Experimental design at each location was a randomized complete block design. Fertility treatments for winter wheat included an unfertilized control (PL₀N₀), inorganic N fertilizer (120 lb acre–¹, PL₀N₁₂₀), PL at the rate of 40 lb N acre–¹ plus 80 lb acre–¹ inorganic N (PL₄₀N₈₀), PL at the rate of 80 lb N acre–¹ plus 40 lb acre–¹ inorganic N (PL₈₀N₄₀), and PL at the rate of 120 lb N acre–¹ (PL₁₂₀N₀). An unfertilized winter fallow treatment was also included to enable a comparison of yield between the mono- and double-cropped soybean. A combination of PL and inorganic N resulted in wheat yields comparable to those with inorganic N alone while PL alone yielded less. Double-cropping soybeans with winter wheat tended to improve soybean yield when compared with mono-cropped soybeans planted on the same date; however soybean yield was not consistently enhanced by the residual PL nutrients applied to wheat when compared with N fertilizer only treatment.