Abstract: 【Objective】 The objective of this study was to quantify water and nitrogen use efficiencies (WUE and NUE) and their environmental impact under different water and nitrogen management practices, and to provide some suggestions on making optimal management practice. 【Method】 Two kinds of water and nitrogen management practices, farmers’ practice (FP) and reduced input (RI) practice based on real-time measure of soil water content and soil mineral N concentration, were both conducted under winter-wheat and summer-maize rotation system from Oct. 2004 to Sep. 2006 in the North China Plain (NCP). After a Water and Nitrogen Management Model (WNMM) was calibrated and validated, the yields, amounts of drainage, N leaching, WUE and NUE for both treatments were all calculated. 【Result】 The results showed that the difference of the irrigation amounts between the two treatments was small, while the difference of fertilizer application rate was significant, the amounts for RI (540 kg N·hm-2) was only half of that of FP (1 100 kg N·hm-2). The annual average yields under FP and RI practices were 11 579 and 11 748 kg·hm-2, respectively. The WUE for FP and RI were 1.65 and 1.72 kg·m-3, respectively. Their NUE were 15 and 24 kg·kg-1 N, respectively. N leaching and NH3 volatilization were the main pathway of nitrogen loss. Amounts of N leaching were 407 and 104 kg N·hm-2 for FP and RI, respectively, and NH3 volatilization was 282 and 104 kg N·hm-2 for FP and RI, respectively. 【Conclusion】The yield, WUE and NUE under RI were all higher than those under FP, and total N loss under RI was significantly lower than that under FP.Therefore, water and nitrogen management by farmers’ practice should be improved to develop sustainable agriculture in the NCP.

Key words: North China Plain, water and nitrogen management model, drainage, nitrogen leaching, water and nitrogen use efficiencies