Winter Wheat Yield Response to a Urea Amended with a Urease Inhibitor and Fertilization Time

Abstract

Amending urea with a urease inhibitor may be of benefit in reducing NH losses and increasing winter wheat (Triticum aestivum L.) grain yield. Our primary objective was to evaluate wheat yield as affected by urea amended with and without the urease inhibitor Agrotain applied at four different times at a suboptimal N rate. A secondary objective was to evaluate wheat yield response to N rate across four N application times. Six trials were established on silt loam soils in eastern Arkansas with 75 lb N/acre as urea and Agrotain-treated urea applied from mid-February through early April. Five trials also included 125 lb N/acre as Agrotain-treated urea to evaluate wheat yield response to N fertilization rate and time. Averaged across 24 N applications, wheat fertilized with Agrotain-treated urea produced yields that were 3% greater than urea alone. Categorizing the N source yield differences for each fertilization event showed that Agrotain-treated urea increased wheat grain yields by 0%, 6.9%, 10.3%, and 27.1% above that of wheat fertilized with urea for 14, 5, 3, and 2 of the 24 fertilization events, respectively.. Wheat receiving 125 lb N/acre produced yields that were 7% to 15% greater than wheat receiving 75 lb N/acre at four of five sites. Wheat yield response to N application time depended on site-year and suggested that N should be applied before Feekes stage 6.