Effects of nitrogen fertilizer application and irrigation level on soil nitrate nitrogen accumulation and water and nitrogen use efficiency for wheat/maize intercropping

In order to improve nitrogen and water use efficiency, effects of nitrogen fertilizer application and irrigation level on soil nitrate nitrogen accumulation and water and nitrogen use efficiency for wheat/maize intercropping were conducted in Hexi corridor of Gansu Province with three nitrogen rates (0, 225 and 450 kg/hm² ) and three irrigation levels (750, 1125, 1500 m3/hm²). The results showed that irrigation level and nitrogen rate affected little on nitrate nitrogen accumulation of wheat strip, yet significantly affected maize strip. With the increase of nitrogen rate, nitrate nitrogen accumulation of maize strip increased .With the increase of irrigation level and nitrogen rate, relative nitrate nitrogen of soil in 0～60 layer increased, and that of soil in 60～140 cm decreased. Apparent nitrogen utilization rate by plant, nitrogen production rate and the ratio of output to input were the biggest at 225 kg/hm² of nitrogen rate, but there was no significance among different irrigation levels. Water use efficiency was the highest at W₇₅₀N₂₂₅, and lowest at W₁₅₀₀N₀. With the increase of irrigation level, water use efficiency decreased.