Effect of a new urease inhibitor on ammonia volatilization and nitrogen utilization in wheat in north and northwest China

Field experiments were conducted at three typical wheat-maize double-cropping sites in north and northwest China to investigate ammonia (NH3) volatilization from urea and from urea amended with 0.12% (w/w) Limus® (a new urease inhibitor consisting of 75% N-(n-butyl) thiophosphoric triamide (NBPT) and 25% N-(n-propyl) thiophosphoric triamide (NPPT)) in winter wheat. Grain yields and nitrogen (N) budgets of all N treatments were also evaluated to investigate the effects of urea-N application rates and Limus during one wheat season. Cumulative NH3 losses after two weeks for conventional urea were 11-25% of applied N, while those for urea amended with Limus were only 0-6% of applied N. The urease inhibitor increased fertilizer N retention more strongly when soil and environmental conditions promoted extensive NH3 losses. However, grain yields were not significantly (P > 0.05) enhanced by Limus compared to conventional urea at all three sites. A clear increase in apparent N recovery efficiency (REN) with Limus (ranging from 10 to 16%) resulted at the Quzhou (QZ) site compared to equal amounts of optimized urea-N, with an increase in REN of up to 65% under a further 20% N-reduced urea amended with Limus treatment. The study also demonstrated the urgency of appropriate fertilizer N management in China.