Effect of topdressing nitrogen of intercropped maize strip on intercropped crop yields and soil nitrate nitrogen as well as its residual effect

【Objective】 This paper aimed to clear effect of different topdressing nitrogen in maize strip on dynamic changes of crop yields and soil nitrate nitrogen, and to clarify residual effect of different nitrogen in intercropping systems on agronomy and environmental effect of sequent crops in winter. 【Methods】 For maize intercropped with soybean in summer, both maize and soybean were applied the same basal fertilizer (N 45 kg/hm2). Then all soybean strips had no topdressing, and different topdressing nitrogen amounts (N 0, 75 and 180 kg /hm2) were set in the maize strip forming three treatments (N0, N75 and N180). The dynamic changes of biomass and soil nitrate were monitored during key growth periods of maize and soybean, and comparative analysis was used to determine the residual effect of each treatment on wheat yield and soil nitrate accumulation after wheat harvest. 【Results】 The results show that the biomass, yield and nitrogen accumulation of maize are not significantly increased as the increase of topdressing nitrogen of maize strip, and the amounts of topdressing nitrogen have no effects on soybean biomass, yield and nitrogen accumulation. There is significant effect on soil nitrate N content, and after the topdressing nitrogen, the soil nitrate N content of 0-20 cm soil has a marked increase and the soil nitrate N content of 20-40 cm has little change. The more topdressing nitrogen, the higher soil nitrate N content of maize and soybean strips in every key growth period, and the soil nitrate N accumulation after the crop harvest is also high. In the intercropping system, the topdressing N 180 kg/hm2 increases the soil nitrate N accumulation by 12%-25% compared to the other two treatments. In addition, the yield and nitrogen accumulation of wheat are not increased with the increase of topdressing nitrogen of maize strip in summer, but the 0-100 cm soil nitrate accumulation after the wheat harvest is increased with the increase of topdressing nitrogen. Compared to the intercropping system with only basal fertilizer but no topdressing, the topdressing nitrogen increases the 0-100 cm soil nitrate accumulation after the wheat harvest by 22.38%-70.18%. 【Conclusions】 In the intercropping system, only basal nitrogen application (N 45 kg/hm2) in maize, or a small amount of topdressing nitrogen (N 75 kg/hm2) following with basal nitrogen application would also be feasible. With the N management, the total yield of intercroping system would not be impacted, and the residual NO-3-N content in 0-100 cm soil of following winter wheat would be low.