Determination of Poultry Litter's Nitrogen-Fertilizer Value for Winter Wheat Production.

The availability of N in poultry litter (PL) for cool-season crop production is poorly documented. Currently, in Arkansas, there are no recommendations for using PL as a N fertilizer source for winter wheat (Tritcum aestivum L.) production. The research objective was to determine the inorganic-N fertilizer equivalence of PL applied in late summer to winter wheat based on N uptake and grain yield. Field experiments were established in September 2009 on a Calhoun and Memphis silt loam in eastern Arkansas. Selected plots received 0, 84 and 168 kg N/ha as PL applied 6 weeks before planting (mid September) or at planting.  The urea-N equivalency of PL-N was determined based on N uptake (Feekes 10.5) and grain yield responses of wheat fertilized with 22 to 191 kg N/ha applied in February and March as a blend of urea and ammonium sulfate (UASB). Wheat N uptake and yield responses to UASB-N rate were characterized using linear or quadratic models.  Nitrogen uptake by wheat receiving 84 and 168 kg PL-N/ha was numerically, but not statistically (P<0.10) different from wheat receiving no N. At the two sites, wheat fertilized with no N had N uptake means of 73 to 77 kg N/ha, compared to 91 to 113 kg N/ha on the Memphis soil and 96 to 141 kg N/ha on the Calhoun soil for wheat receiving PL-N.   Grain yield of wheat receiving no N averaged 3028 kg/ha on the Memphis soil and 2960 kg/ha on the Calhoun soil. Application of PL produced average yield increases of 740 kg/ha at both sites.  Wheat grain yield increased curvilinearly as UASB-N rate increased with all coefficients, depending on site.  The average urea-N equivalence of PL-N was 23% on the Memphis soil and 38% on the Calhoun soil. Results suggest the recovery of PL-N by wheat is low.