Nitrogen-Fertilizer Equivalence of Poultry Litter for Winter Wheat Production

The N availability of manure applied to summer-grown crops has been frequently researched, but information regarding the N-fertilizer equivalence of manure for winter-grown crops is lacking. Our objectives were to determine the inorganic N-fertilizer value of poultry litter (PL) compared with applying urea-N fertilizer to wheat (Triticum aestivum L.) in late winter and examine the inorganic-N content in PL-amended soils at 5, 15, and 25 degrees C. Six field experiments compared PL applied preplant or at planting at 84 and 168 kg N ha(-1) to wheat fertilized with urea-ammonium sulfate blend (UASB) rates of 0 to 191 kg N ha(-1). The apparent N uptake efficiency of PL-N ranged from 0 to 63 and 8 to 56% for wheat receiving 84 and 168 kg PL-N ha(-1), respectively. The time of PL application had no effect on wheat N uptake and yield at four of five sites. The mean potentially available N (PAN) values for N uptake at Feekes stage 10.5 and grain yield were 0.31 and 0.39 kg UASB-N kg(-1) PL-N, respectively. Soil amended with PL incubated at 15 and 25 degrees C showed that 19 to 31% of the added PL-N was mineralized and recovered as NO3-N in 28 to 44 d. When the incubation temperature was reduced to 5 degrees C, 17 to 19% of the PL-N was recovered as NO3-N or NH4-N with <3% recovered as NO3-N. The results suggest winter wheat growers that apply PL in the fall can subtract 30 to 40% of the PL-N from the late-winter N fertilizer rate.