Mitigation of ammonia volatilization with application of urease and nitrification inhibitors from summer maize at the Loess Plateau

Field experiments were conducted at three sites: Yangling (YL); Zhouzhi-1 (ZH-1) and Zhouzhi-2 (ZH-2) of the Loess Plateau during summer maize crop, to investigate the effectiveness of N-(n-butyl) thiophosphoric triamide (NBPT) and NBPT + dicyandiamide (DCD) with urea on reducing NH3 volatilization from different soils under different environmental conditions. Four treatments including control (no N), N-220 kg/ha, N-220 + NBPT and N-220 + NBPT + DCD were applied in two splits through the band placement method. Total NH3-N loss observed were 65.8, 40.5 and 20.1 NH3-N kg/ha (accounting for 29.9, 18.4 and 9.2% of N applied) from urea for YL, ZH-1 and ZH-2, respectively. The application of NBPT and NBPT + DCD significantly reduced NH3 volatilization by 80-93% and 75-90%, respectively. The meteorologic factors such as precipitation, air temperature and wind speed significantly affected NH3 volatilization. These results suggested that the amendment of urea with NBPT and NBPT + DCD have potential to mitigate NH3-N losses from alkaline soils in the Loess Plateau.