Effect of irrigation on soil NO^-₃-N accumulation and leaching in maize/barley intercropping field

Before and after each irrigation, NO^-₃-N concentration in 0～200 cm soil and 135 cm deep leachate of maize/barley intercropping was determined in Hexi corridor of Gansu Province, with three rates of nitrogen application(0, 150, 300 kg/hm²), two rates of irrigation level (816, 1632 m³/hm²). The results showed that irrigation obviously affected soil NO^-₃-N accumulation, and it reduced with the increase of irrigation times. In comparison with lower irrigation level, high rate irrigation accelerated NO^-₃-N reduction. NO^-₃-N concentrations in leachate from both barley and maize strip at first irrigation were the highest, they reached 8.04～17.21 mg/L and 3.30～14.57 mg/L, respectively. After three times irrigations, NO^-₃-N leachate in maize strip was the highest with the treatment that the level of N fertilizer application was 150 kg/hm² and irrigation quantity was 1632 m³/hm², with average content reaching 4.31 kg/hm². NO^-₃-N leachates in barley strip were higher with treatment that the level of N fertilizer application was 150 kg/hm² and irrigation quantity was 1632 m³/hm² and treatment that the level of N fertilizer application was 150 kg/hm² and irrgation quantity was 816 m³/hm², respectively, with average content reaching 6.82 kg/hm².