Evaluation of nitrogen fate, water and nitrogen use efficiencies of winter wheat in North China Plain based on model approach.

Water scarcity and nitrate contamination in groundwater are serious problems in the North China Plain (NCP). The objective of this study was to compare the effects of farmer's practice and optimal water and nitrogen management on nitrate leaching, and water and nitrogen use efficiencies (WUE, NUE) during winter wheat season in the NCP. A winter wheat experiment with four treatments (traditional irrigation plus traditional fertilizer, W1N1; traditional irrigation plus optimal fertilizer, W1N2; optimal irrigation plus traditional fertilizer, W2N1; optimal irrigation plus optimal fertilizer, W2N2) was conducted from October 1999 to June 2001 in Beijing suburban. The soil–plant system, water and solute transport model was calibrated and validated based on the data collected from the experimental field, then the model was used to simulate the water movement, nitrogen (N) transport, and crop growth process. The results showed that the simulated soil water content, nitrate concentration in the soil profile, leaf area index, crop N uptake, and grain yield were all in good agreement with the measured data. The simulated results indicated that the improved management of water and fertilizer practice could increase crop yield, and reduce water drainage, nitrate leaching, and gaseous N loss compared to farmers' practice. WUE and NUE under improved practice were 1.36 kg m−3and 34.9 kg kg−1N−1in 2000, 1.07 kg m−3and 31.5 kg kg−1N−1in 2001, respectively. Compared to farmers' practice, the optimal management practice can save water about 4–19%, water drainage decreased 50–65%, N leaching reduced over 90% and gaseous N loss decreased about 70%, at same time leading to an increase in WUE and NUE by 10.6% and 10.3% in 2000, 64.5% and 98.3% in 2001, respectively. [ABSTRACT FROM AUTHOR]