Soil Moisture Controls the Denitrification Loss of Urea Nitrogen from Silty Clay Soil

Relative control of soil moisture [30, 60, and 80 percent water-holding capacity (WHC)] on nitrous oxide (N₂O) emissions from Fargo-Ryan soil, treated with urea at 0, 150, and 250 kg N ha^?1 with and without nitrapyrin [2-chloro-(6-trichloromethyl) pyridine] (NP), was measured under laboratory condition for 140 days. Soil N₂O emissions significantly increased with increasing nitrogen (N) rates and WHC levels. Urea applied at 250 kg N ha^?1 produced the greatest cumulative N₂O emissions and averaged 560, 3919, and 15894 µg kg^?1 at 30, 60, and 80 percent WHC, respectively. At WHC ≤ 60 percent, addition of NP to urea significantly reduced N₂O losses by 2.6- to 4.8-fold. Additions of NP to urea reduced N₂O emission at rates similar to the control (0 N) until 48 days for 30 percent WHC and 35 days for 60 and 80 percent WHC. These results can help devise urea-N fertilizer management strategies in reducing N₂O emissions from silty-clay soils.