On the basis of the isograms, we analyzed the variation law of yield and grain protein content with soil water content, nitrogen and P2O5,.

• 用等值线图描述产量和蛋白质含量的水氮和氮磷两因素效应，分析产量和蛋白质含量变化规律及其关系，确定实现一定生产目标的水肥管理方案。