Formation Of Grain Yield And Utilization Of Water And Nutrients For Winter Wheat Affected By Nitrogen And Phosphorus

Nitrogen (N) and phosphorus (P) are essential nutrients for crop, and paly important role in increasing yield and quality of dry land crops. However, the over application of N and P fertilizers could not only lead to a decreaed economic efficiency of agriculture production, but also bringing the serious pressure to environment. Therefore, based on conventional cropping system, the rotation of winter wheat and summer maize, this research was mainly to study how nitrogen and phosphorus to influence crop yield, dry matter accumulation, the absorption of water and nutrients, and the distribution of soil moisture, nitrate N and ammonium N in profiles, by applying N and P fertilizers before the seeding of winter wheat and no fertilizer applycation during summer maize growing season. The objectives were to understand the reasons for the decrease of crop yied and the accumulation of nitrate N in the soil with applying exessive N and P fertilizers. The main results were as follows:1.No significant differences were found for winter wheat biomass over N rates, but harvest indexes were significantly different. The increase of harvest index and grain yield of winter wheat were not obvious signicant when N rate was or exess 160 kg ha-1. This indicates that it is one of important reason for wheat yield increase by enhanced harvest index with applying N. Not only couldn't exessive N fertilizer improve harvest index, but also led to the great loss of biomass and nutrients of N, P, K at late growth stage of winter wheat, and thus the phenomenon of more fertilizers but less yield occurred2. There was no significant difference for winter wheat harvest index among P rates. Therefore, the main reasons for the increase of grain yield caused by optimum P rate was owing to accelerating biomass accumulation, but not to improving the translocation of dry matter from vegetative parts to grain at late growth stages. Excessive P application could not only decrease water accumulation at the early growth stages, but also increase the losses of biomass, water, N, P and K at the late growth stages, and therefore caused the decrease of grain yield of winter wheat.3. During winter wheat growing season, soil moisture was greatly decreased. The application of N and P fertilizers could accelerate crop growth, as well as increase soil moisture consumption. During summer maize growing season, soil moisture could be well restored, especially in the plots with no N fertilizer applied at the former season.4. In fields with more nitrate N residual in the soil, optimum fertilization could distinctly decreased nitrate N in deep soil when planting winter wheat. However, excessive N fertilization could led nitrate N remaining in the upper soil layer, which would accumulate in soil profile year by year and leach to the deep soil in rainy summer. The change of ammonium N in soil profile is less consistent compared to soil moisture and nitrate N at different crop seasons and fertilization treatments. However, the mass of ammonium N in soil profile was less in the system of winter wheat-summer maize rotation compared to that in the monoculture of winter wheat. Fallow with no tillage tended to increase ammonium N in soil profile after winter wheat harvest, and decreased after summer maize.