Nitrogen‐Fertilizer Equivalence of Poultry Litter for Winter Wheat Production

Abstract

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°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°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°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.