COMBINED NITROGEN AND PHOSPHORUS APPLICATION SYNERGISTICALLY REGULATE GRAIN YIELD AND PROTEIN CONTENT IN WINTER WHEAT (TRITICUM AESTIVUM L.)

To provide technical support for better quality and to get high-yield of winter wheat in Shanxi Province, four winter wheat genotypes are investigated in the field experiments to reveal the synergistic change regularity of grain protein content and yield, determine the protein threshold of winter wheat, and obtain the optimum fertilization application of nitrogen (N) and phosphorus (P).The study depicts P has a significant effect on the protein content and yield of winter wheat.Increasing the application rate of P can significantly increase the yield, while its influence on protein content varies within different varieties.Similarly, application rate of N has a prominent effect on both yield and protein content as both of which are enhanced with the increase of N application.We also record a synergistic increase in yield and protein content between certain intervals; the yield and protein content increase first, and then decrease with increasing applications of N fertilizer, which can be characterized with a parabola.Applying the appropriate amount of N and P can cause a synergistic increase for protein content and yield, and the most ideal threshold intervals of protein corresponding to the optimal P and N application rate are 150 kg/ha-200 kg/ha and 180 kg/ha-255 kg/ha, respectively.