Impacts of ammonia volatilization from broadcast urea on winter wheat production

Abstract

Abstract Ammonia (NH 3 ) volatilization from broadcast urea may lead to significant N losses in winter wheat. We aimed to: (a) quantify N losses through NH 3 volatilization from fields fertilized with urea and urea amended with a urease inhibitor (NBPT) under cold weather months (February–April), and (b) investigate the impact of N losses through NH 3 volatilization on the winter wheat production. We employed the integrated horizontal flux (IHF) method with passive NH 3 samplers to quantify NH 3 volatilization at five sites in Kansas. Urea and urea + NBPT were broadcast at a rate of 60 kg N ha –1 over circular plots. We assessed the impact of NH 3 losses on wheat at three sites employing different rates of urea and urea + NBPT. NH 3 losses volatilization varied from 0.3 to 29.6% of total N applied. The largest N losses (>23% of applied N) occurred when urea was broadcasted to moist soils followed by a dry period. Amending urea with NBPT reduced NH 3 volatilization losses by more than 20% on the campaigns with the largest N losses (>23%). However, our results showed no significant differences for wheat yield, N‐recovery and agronomic efficiency between urea and urea + NBPT treatments likely due to the reduced NH 3 volatilization (<17%) where the impact on winter wheat was measured. Our results suggest that winter wheat farmers should carefully evaluate the soil surface moisture conditions before broadcasting urea to avoid potential NH 3 volatilization losses even under cold conditions (average soil temperature ranging from 2.5 to 7.7 °C).