关键词: 减量施N, 冬小麦-夏玉米种植体系, 硝态氮残留, N平衡

Abstract: A field trial on a calcareous soil was carried out at an experimental station of China Agricultural University with the objective of assessing the effect of reduced nitrogen application on N utilization and N balance in a winter wheat-summer maize cropping system.Before this study,the trial has been conducted for one rotation cycle of wheat and maize with four-fixed N rates of 0,120,240 and 360 N kg·hm^-2 per crop.In this study,each plot was divided into two sub-plots for two N application rates:normal N application(original rate) and reduced N application(reduced rate).The results showed that the grain yields of wheat and maize reached the platform at N rate of 120 kg·hm^-2(N₁₂₀),and then almost kept the same level regardless of the further increase of N rate(N₂₄₀ and N ₃₆₀).The N uptake by wheat and maize followed the similar tendency like their yield.The grain yield and N uptake of wheat were not significantly declined with the half reduction of original N rate except the treatment N 120.However,the same items in maize significantly declined with the further reduction of N fertilizer to zero.The residual NO₃^--N(main source of mineral N) in reduced N sub-plots was significantly lower in 0～1 m soil layer,but not different in 1～2 m soil layer compared with those receiving original N rate,indicating that 1～2 m soil NO₃^--N could hardly be utilized by crops.N balance calculation further showed that the N recovery by crops could be largely raised by the reduction of N fertilizer,while the apparent N loss rate decreased in wheat-maize rotation,respectively.Thus,the reduction of fertilizer N under high N rate can significantly increase N use efficiency and reduce NO₃^--N accumulation and apparent N loss.

Key words: Reduction of N application, Wheat-maize cropping system, Residual nitrate N, N balance