Effect of Irrigation on Mineral Nitrogen Concentration in Soils of Maize/Barley Intercropping

Before and after each irrigation, the mineral nitrogen concentration in 0~200 cm soil of maize/barley intercropping was determined in Hexi corridor of Gansu province, this research arranges the 3 level of nitrogen application (0,150,300 kg/hm2), 2 level of irrigation water (816,1 632 m3/hm2). The results showed that soil mineral nitrogen concentration was higher at 0~60 cm depth before irrigation, yet it decreased obviously after irrigation, furthermore, soil mineral nitrogen content was more affected by the first and second irrigation.With 150 kg/hm2 nitrogen application,the mineral nitrogen loss of barley strip were 136.06 kg/hm2 after 816 m3/hm2 water irrigation ,and 142.93 kg/hm2 after 1 632 m3/hm2 water irrigation,which account for 90.70% and 95.29% of nitrogen fertilizer application, yet maize strip were 95.28 kg/hm2 and 115.89 kg/hm2,which account for 63.52% and 77.26% of nitrogen fertilizer application. With 300 kg/hm2 nitrogen application, the mineral nitrogen loss of barley strip were 264.43 kg/hm2 after 816 m3/hm2 water irrigation, and 237.72 kg/hm2 after 1 632 m3/hm2 water irrigation,which account for 88.14% and 79.24% of nitrogen fertilizer application, maize strip were 163.06, 257.76 kg/hm2,which account for 54.35% and 85.92% of nitrogen fertilizer application. Among three irrigation,the mineral nitrogen loss was the highest at the second irrigation with 150 kg/hm2 nitrogen application,and the first irrigation with 300 kg/hm2 nitrogen application, yet the barley strip all were the highest with the first irrigation. It suggested that mineral nitrogen loss was first decided by nitrogen fertilizer rate, then irrigation rate.