Evaluation on the irrigation and fertilization management practices under the application of treated sewage water in Beijing, China

Irrigation and fertilization management practices play important roles in crop production. In this paper, the Root Zone Water Quality Model (RZWQM) was used to evaluate the irrigation and fertilization management practices for a winter wheat-summer corn double cropping system in Beijing, China under the irrigation with treated sewage water (TSW). A carefully designed experiment was carried out at an experimental station in Beijing area from 2001 to 2003 with four irrigation treatments. The hydrologic, nitrogen and crop growth components of RZWQM were calibrated by using the dataset of one treatment. The datasets of other three treatments were used to validate the model performance. Most predicted soil water contents were within ±1 standard deviation (S.D.) of the measured data. The relative errors (RE) of grain yield predictions were within the range of -26.8% to 18.5%, whereas the REs of biomass predictions were between -38% and 14%. The grain nitrogen (N) uptake and biomass N uptake were predicted with the RE values ranging from -13.9% to 14.7%, and from -11.1% to 29.8%, respectively. These results showed that the model was able to simulate the double cropping system variables under different irrigation and fertilization conditions with reasonable accuracy. Application of RZWQM in the growing season of 2001-2002 indicated that the best irrigation management practice was no irrigation for summer corn, three 83mm irrigations each for pre-sowing, jointing and heading stages of winter wheat, respectively. And the best nitrogen application management practice was 120kgNha⁻¹ for summer corn and 110kgNha⁻¹ for winter wheat, respectively, under the irrigation with TSW. We also obtained the alternative irrigation management practices for the hydrologic years of 75%, 50% and 25%, respectively, in Beijing area under the conditions of irrigation with TSW and the optimal nitrogen application.