Impacts of ammonia volatilization from broadcast urea on winter wheat production

Ammonia (NH3) volatilization from broadcast urea may lead to significant N losses in winter wheat. We aimed to: (a) quantify N losses through NH3 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 NH3 volatilization on the winter wheat production. We employed the integrated horizontal flux (IHF) method with passive NH3 samplers to quantify NH3 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 NH3 losses on wheat at three sites employing different rates of urea and urea + NBPT. NH3 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 NH3 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 NH3 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 NH3 volatilization losses even under cold conditions (average soil temperature ranging from 2.5 to 7.7 <degrees>C).