Effects Of Nitrogen Fertilizer On Yield Of Winter Wheat And Straw Decomposition Under Maize Straw Returning In Guanzhong Irrigation District

Nitrogen is the essential nutrient element in crop growth and development process,unreasonable use, will lead to excess nitrogen lost through leaching, volatilization, and otherways. Nitrogen in a huge loss not only makes people in economic losses, but also pollutes theenvironment; pose a potential threat to human health. Therefore how to through the effectiveway to reduce nitrogen fertilizer, increase crop yields and improve soil physical and chemicalproperties has become the focus on solving the urgent research in agricultural production.Crop straw is an important biological resource in crop production system, rich in nitrogen,phosphorus, potassium, calcium, magnesium and organic matter and so on, which hascomprehensive utilization value. With the development of agricultural production, straw hasbecome an effective way for the use of straw resources in agricultural production. Straw canalleviate the imbalance of nitrogen, phosphorus, potassium in the soil, to make up for theshortage of phosphorus, potassium fertilizer. Straw returning can rise to reduce the amount ofchemical fertilizer effect, but the straw decomposition process is very complex, and affectedby the external environment and soil nutrient. For this purpose, we need to make effort tosolve the problem of declining crop yield and quality of crop straw waste of resource andfertilizer management practice caused by the improper, reveal the different nitrogen level oncorn straw decomposition and nutrient release rule and provide the basis for the rationalutilization of straw resource and farmland nutrient scientific management.Through the straw returning and N fertilizer trial experiment, methods of using nylonbag and sampling analysis, the following conclusions were drawn:1. Both with straw returning and nitrogen fertilization, grain yield of winter wheat wassignificantly higher than that of only nitrogen fertilization; the increasing rate was18.5%.When the nitrogen fertilization was262.5kg·hm^-2, the winter wheat yield was the highest, upto8415kg·hm^-2. Effective panicle number, grains per spikes,1000-grain weight, yield andnitrogen use efficiency were390000/hm2,1.57grain,2.11g,1204kg·hm^-2and5.82%,respectively form the treatment of fertilizer plus maize straw, respectively higher than thoseform the treatment of fertilizer. 2. Water use efficiency was4.14,6.9,9.32and8.47kg hm2·mm, respectively form thetreatments of fertilizer plus maize straw, higher than those form the treatment of maize straw.The water Consumption of straw returning was reduced13.70mm compare with not returning.Straw returning and nitrogen fertilization by262.5kg·hm^-2are most conducive to the growthof winter wheat and the highest yield. Soil nitrate nitrogen accumulation amount of S+N175was less than the amount of N175; nitrate nitrogen accumulation amount was reduced55.7kg·hm^-2. The amount of nitrate reduced were9.7,15.1kg·hm^-2which form S+N175comparedwith N175in0～40,140～200cm。3. Corn straw decomposition tests with method of using nylon bag showed: Thedecomposition rate of crop straws was much faster at the beginning stage, the dry matterresidue remained at58.36%～63.4%after straw returned87days. Potassium was basicallycompletely released at the beginning stage （0-10d）, the release ratio of nitrogen, phosphoruswas relatively slow, and the emission of nitrogen, phosphorus and potassium was35.27%-43.30%,27.82%-35.52%,83.07%-87.29%. Different amounts of nitrogen had nosignificant effect on P and K release. Available Fe, Zn was released of state in the process ofdecompose, Fe showed rapid release state in0-10days, the content of Fe was unchanged after10days. Available Zn was released in the0-30days, the content of available Zn wasunchanged after30days.4. With the extension of years of wheat-corn straw returned, the content of soil organicmatter also showed increasing trend. The contents of soil organic matter were increased to1.26,1.38,1.71,1.74mgkg-1which the growth rates were9.0%,9.9%,12.3%,12.5%afterstraw returning3～6years. Years of straw returning were not related to amounts of soilavailable Fe, Mn, Zn.