Effects of biochar amount on NH3 volatilization in summer maize fields under different irrigation conditions

Abstract NH3 from farmland has serious impacts on human health and ecosystems. To reduce NH3 volatilization and increase yield, biochar is applied. A field experiment was carried out to study NH3 volatilization loss, and summer maize yield was analysed under different irrigation schemes with different amounts of biochar. Two irrigation schemes, I1 (67.5 mm) and I2 (121.5 mm), were set up according to the irrigation habits of local producers. Three biochar application rates were selected: C1 (0 t ha-1), C2 (20 t ha-1) and C3 (40 t ha-1). The relationship between NH3 volatilization and influencing factors, including NH4+-N concentration, NO3--N concentration, pH in the 0~20 cm soil layer and temperature, was investigated. The results showed that the yield significantly (p<0.05) increased by 17.27%~46.67% after applying biochar. Compared with C1, NH3 volatilization significantly (p<0.05) decreased by 28.98%~31.63% in C2, while that in C3 significantly (p<0.05) increased by 22.64%~73.87%. The effects of biochar on NH3 volatilization were consistent under different irrigation conditions. Compared to I1, I2 not only increased the yield of summer corn but also increased the risk of NH3 volatilization and leaching. NH3 volatilization was positively correlated with NH4+-N concentration, pH and temperature, but it was negatively correlated with NO3--N concentration. These results suggest that the optimal application amount of biochar for summer maize ranges from 14.59 t ha-1 to 17.19 t ha-1 in the study area.