USE AND MANAGEMENT OF SOIL WATER AND NITROGEN RESOURCES Ⅲ The optimal management of soil water and nitrogen resources

On the condition of winter wheat summer corn cropping system in Beijing, the nonlinear goals programming model was used to optimize the water and nitrogen management under various rainfall year types. A linear approaching method was chosen to solve the above model. The total amounts of irrigation and nitrogen applied was employed as the programming variables. Grain yield was set as the first preferential goal, and the use efficiency of water and nitrogen resources within 1 m soil depth as the second preferential goal. The objective functions were obtained from the simulation results of grain yield and use efficiency of soil water and nitrogen resources under different conditions by applying the crop soil combined model in this study. Finally, the optimal ranges of irrigation and nitrogen application rates were obtained for both single growth season of winter wheat or summer corn at different rainfall year types and annual of winter wheat summer corn at normal rainfall year type.