Combined use of NBPT and micronutrients in granulated or coated urea: A new approach to reduce ammonia volatilization losses from soil

Abstract N‐ ( n ‐Butyl) thiophosphoric triamide (NBPT) is the most widely adopted urease inhibitor, used to reduce ammonia (NH 3 ) volatilization from urea. Micronutrients such as boron (B), zinc (Zn), nickel (Ni) and molybdenum (Mo) are also reported to inhibit urease, serving simultaneously as plant nutrients. However, there is little information on the potential synergistic or antagonistic effects of NBPT and micronutrients on urea protection. The aim of this study was to evaluate NH 3 volatilization losses, soil pH and soil mineral nitrogen content (‐N and ‐N) after application of urea coated or granulated with the micronutrients B, Zn, Ni or Mo, individually. Thereafter, the fertilizers were applied combined and not associated with NBPT. Ammonia volatilization was measured in a closed static chamber under controlled conditions. Urea granulated with B and Zn reduced NH 3 ‐N volatilization circa 30% compared with untreated urea, while Mo and Ni had no effect. NBPT stabilizer had the greatest effect on NH 3 ‐N volatilization (44%–59% reduction), but was less effective (only 20%–34% reduction) when urea was coated with B, Zn or Mo. On the other hand, when B and Zn were incorporated via granulation, the efficiency of NBPT was not reduced, likely because of the physical separation. These findings demonstrate that granulating urea with B or Zn combined with an NBPT‐coating can be a valuable strategy to reduce NH 3 volatilization losses while also supplying micronutrients and hence potentially increase yields in agricultural production systems.