Impact of urease inhibitor on ammonia and nitrous oxide emissions from temperate pasture soil cores receiving urea fertilizer and cattle urine

New Zealand's intensively grazed pastures receive the majority of nitrogen (N) input in the form of urea, which is the major constituent of animal urine and the most common form of mineral N in inorganic N fertilizers. In soil, urea is rapidly hydrolyzed to ammonium (NH₄⁺) ions, a part of which may be lost as ammonia (NH₃) and subsequently as nitrous oxide (N₂O), which is a greenhouse gas. Two glasshouse experiments were conducted to study the effect of a urease inhibitor (UI), N-(n-butyl) thiophosphoric triamide (NBPT), commercially named Agrotain, applied with urine and urea on urea hydrolysis and NH₃ and N₂O emissions. Treatments included the commercially available products Sustain Yellow (urea+Agrotain+4% sulfur coating), Sustain Green (urea+Agrotain) and urea, and cattle urine (476kgNha^-1) with and without Agrotain applied to intact soil cores of a fine sandy loam soil. The addition of Agrotain to urine and urea (i.e. Sustain Green) reduced NH₃ emission by 22% to 47%, respectively. Agrotain was also effective in reducing N₂O emissions from urine and Sustain Green by 62% and 48%, respectively. The reduction in N₂O emissions varied with the type and amount of N applied and plant N uptake. Plant N uptake was significantly higher in the soil cores receiving Agrotain with urea than urea alone, but the slight increase in dry matter yield was non-significant. Hence, urease inhibitor reduced N losses through NH₃ and N₂O emissions, thereby increasing plant uptake of N.