Urease Inhibitor NBPT on Ammonia Volatilization and Crop Productivity: A Meta‐Analysis

Abstract

Core Ideas The volatilization losses averaged 31.0% of applied N for urea and 14.8% for NBPT‐treated urea. NBPT‐treated urea showed a potential yield increase of 5.3% for major crops. The effect of NBPT in reducing volatilization losses were reduced under high N rates. NBPT had a limited effect on increasing yield in coarse‐textured soils and for NBPT rates >1060 mg kg−1. The urease inhibitor N‐(n‐butyl) thiophosphoric triamide (NBPT) slows urea hydrolysis, reduces NH3 volatilization loss, and enhances N availability to plants. Even though most studies have proved the potential of NBPT‐treated urea to reduce NH3 loss, the benefits to increase crop yield have been less consistent, mainly because N is not always the limiting factor. A meta‐analysis was carried out to evaluate the effect of soil properties (e.g., soil pH, soil texture, soil organic C [SOC]), N rate, and NBPT concentration on NH3 volatilization loss and crop yield when comparing urea with NBPT‐treated urea. Regression analysis indicated cumulative NH3 loss of 31.0 and 14.8% of applied N for urea and NBPT‐treated urea, respectively, a 52% reduction in NH3 loss by using the urease inhibitor. The use of NBPT delayed NH3 loss. It took 4.8 and 8.3 d for 50% of the total NH3 loss to occur for urea and NBPT‐treated urea, respectively. The meta‐analyses indicated that when compared with urea, NBPT‐treated urea reduced NH3 volatilization loss across all soil pH classes, soil texture classes, SOC contents, N rates, and NBPT concentrations. The meta‐analysis indicated an average crop yield increase of 5.3% for NBPT‐treated urea compared with urea. This trend was observed for all classes of soil pH, SOC content, and N rate, but yield increases were limited in coarse‐textured soils and NBPT rates >1060 mg kg−1.