Effect of intercropping three legume crops with maize on soil nitrate-N accumulation and distribution in the soil profile

In order to improve nitrogen use efficiency and to reduce environmental pollution from excessive nitrogen application, soil nitrate-N content and accumulation in intercropped legumemaize under 0 and 225 kg(N)·hm^-2 application were investigated in the Hexi Corridor of Gansu Province. The results show that soil nitrate-N accumulation in intercropped faba bean, soybean, pea and maize is lower than the monocrops under 0 and 225 kg(N)·hm^-2 application at faba bean harvest. Nitrate-N content in the soil profile with intercropped faba bean, soybean and pea is lower than the monocrops, with various effecting depths for different crops. At maize harvest, nitrate-N accumulation in the soil of intercropped faba bean and pea is lower than the monocrops. Under zero nitrogen application, soil nitrate-N accumulation in intercropped soybean is lower than monocropped soybean, and that for maize-faba bean, soybean and pea intercrop higher than the monocrops. Under 225 kg(N)·hm^-2 nitrogen application, soil nitrate-N accumulation in intercropped maize-faba bean and pea is lower than the monocrops, while intercropped soybean and maizesoybean intercrop is higher than the monocrops. Nitrate-N content in 0～60 cm soil profile with intercropped faba bean and pea are lower than the monocrops under zero N application and 225 kg(N)·hm^{-2 N application; while that with soybean lower than the monocrop at zero N application, but higher at 225 kg(N)·hm-2 application. Relative soil nitrate-N accumulation suggests that soil nitrate-N accumulation in intercropping treatments is higher than in monocropping at 0～60 cm, but lower than in monocroping at 100～180 cm.}