Coordinated Variation of Yield and Grain Protein Content in Winter Wheat and Strategies of Irrigation and Fertilization

Objective The aim of the paper was to reveal the coordinated variation of winter wheat yield and grain protein content. MethodBased on pot and field experiments, the effect functions of winter wheat yield and grain protein content were established, in which the soil water content and nitrogen and P2O5 were taken as the effect factors. The function curves revealed the coordinated variation of yield and grain protein content with increase of soil water content (or nitrogen) at different nitrogen levels (or soil water content). And the management plans for high yield and high quality of winter wheat were made according to the coordinated variation of yield and grain protein content. ResultThe variation curves of yield and grain protein content with soil water content (or nitrogen) were convex and concave respectively in low fertility and medium fertility (or soil water content were 50% and 60% of field maximum moisture capacity). The nitrogen between minimum protein content and maximum yield were the nitrogen of coordinated variation of yield and grain protein content in 50% or 60% of soil water content. The variation curves of yield and grain protein content with soil water content (or nitrogen) were convex in high fertility (or soil water content were 70% and 80% of field maximum moisture capacity ), and the soil water content (or nitrogen levels) before maximum protein content (or maximum yield) were the soil water content (or nitrogen levels) of coordinated variation of yield and grain protein content.Conclusion Coordinated variation of yield and grain protein content was possible in suitable condition. The simulated value of yield and grain protein content were standardized using polar difference variant, and the intersection point of curves of the standardized variables was the best combination of yield and grain protein content. The effect of yield and grain protein content with soil water content and nitrogen (or nitrogen and P2O5) was described by isopleth. On the basis of the isograms, we analyzed the variation law of yield and grain protein content with soil water content, nitrogen and P2O5, . We made management plans for high yield and high quality.