Abstract: The study discussed the physiological foundation of supplementary effect for fertilization of N-P combinations in winter wheat, which base on a regimen of economic and rational fertilizations with that appropriate ratio of N.P. K. elements. The result shows that if N or P fertilizer applies alone in the soil of N-P deficiency, the plants grow poorly. Because of, when N fertilizer applied alone, the P deficiency appeared in plants firstly , the content of nucleic acid was lower and inhibited the P metabolism. Even though the N was absorbed and it results in the natrate reductase increased, the content of protein- N was lower. It indicated the P deficency also effected the N- metabolism in plants. On the other hand, when P fertilizer applied alone, the N deficiency appeared in plants firstly, while the N-metabolism was maintained at a low level. Though the P was absorbed, the content of nucleic acid was low. It indicated the N- deficency affected the P-metabolism in plants.Only in the status, when the N and P fertilizer was applied by combination of rational rate and ratio, the contents of different form of N and P compounds involved the nucleic acid and protein both were higher. And only at that time, the N: P ratio was a coordinative proportion, the N and P metabolism was maintained at a normal level. Thus the function of N-P nutriets was maintained well. The plants were vigorous and high yield will be attained.

Key words: Winter wheat, Nitrogen nutrition, Phosphorus nutrition, Combining effect