Effect On Straw Return And Nitrogen Ertilizer Application To Yield Formation Of Inter Wheat And Nutrition Utility In Uangzhong Irrigation Area

Winter wheat-summer corn rotation system is one of the main rotation systemmanagement in Guanzhong irrigation area. Returning straw to field has very importantmeaning to promote agricultural sustainable development. Nitrogen fertilizer has crucialeffect to wheat yield and quality, however, unreasonable application of nitrogen fertilizer willdecrease yield and quality, at the same time cause environment pollution; eventually restrictthe sustainable development and high output and efficiency of agriculture production.A field experiment with six different treatments (on the condition of straw residue returnamount of nitrogen application as0kg/hm~2,87.5kg/hm~2,175kg/hm~2,262.5kg/hm~2,350kg/hm~2respectively and175kg/hm~2without straw residue return) was conducted toinvestigate the effect of nitrogen application amount to winter wheat yield, quality, nutritionabsorption and soil nitrate accumulation.Incubation experiment was conducted to study the decomposing process of straw residueof wheat and corn and reveal the prosperity of organic carbon, nitrogen, phosphorus andpotassium releases from straw residue. The results showed as follow:(1) With the rate of nitrogen fertilizer application increased in the range of0~262.5kg/hm~2, the grain yield and biomass of winter wheat increased significantly. Of the increasingof nitrogen fertilizer application, harvest index of winter wheat showed a changing trend ofdecline after an increase, and get its peak of50.24%, when the amount of nitrogen fertilizerapplication reached175kg/hm~2. The winter wheat yield has a significant effect with number ofspike and grain number. In the range of0~262.5kg/hm~2, with the increase of the amount ofnitrogen application, protein content of grain and protein yield increased significantly, nosignificant result had been showed with the continue increasing of nitrogen fertilizer amount.(2) Rational application of nitrogen fertilizer increased nitrogen content of wheat plantsignificantly, and increased the content of phosphorous in wheat plant while reduce it in wheatplant and grain, in addition, significantly improved the content of potassium in grain. In thecondition of low nitrogen fertilizer application, the absorption of wheat to nitrogen,phosphorous and potassium increased with the increasing of nitrogen fertilizer application, but no significant when the amount of nitrogen fertilizer application is too high. The harvestindex of phosphorous reached its peak with a nitrogen fertilizer application amount of87.5kg/hm~2while the harvest index of N and K get their peak when the nitrogen fertilizerapplication amount is175kg/hm~2. With increasing of the amount of nitrogen fertilizerapplication, there showed a decrease trend in N absorption and utility efficiency, recycleefficiency and efficiency of nitrogen fertilizer production&utility.(3) Nitrate nitrogen accumulation amount in soil increased with the increasing ofnitrogen fertilizer application amount, especially in topsoil. Compared with no nitrogenapplication treatment, the content of nitrate nitrogen in the soil profile of0~20cm and20~40cm are225.6%and159.3%respectively in the treatment of350kg·N/hm~2.(4) When the nitrogen fertilizer application amount is175kg/hm~2compare with nostraw returned treatments, the grain yield and the harvest index of N in the straw returnedtreatments increased significantly, biomass and wheat harvest index in the straw returnedtreatments had increased15.9%and7.4%respectively. Soil nitrate nitrogen accumulatecontent in straw returned treatment showed a decrease of51.42%,36.57%,24.61%,20.80%and25.69%in the soil profile of0~20cm,20~40cm,40~60cm,60~80and80~100cmrespectively.(5) In the incubation experiment, both wheat and corn straw residue decompose processshowed a similar trends that decomposed speed faster in the beginning and become slowergradually later, the dry matter of wheat straw lose32%approximately during the first20daysof decompose process, while the corn straw lose almost43%during the first30days; after80days the dry matter of wheat straw and corn straw approximately lose48%and55%respectively. Both wheat and corn residue decomposition reflect the speed of nutritionelements lose is K＞P＞C＞N, the amount of nutrition elements lose is C＞K＞N＞P. Ureaaddition has an effect of increase the speed of decompose earlier stage, but have no significanteffect to the release process of organic C, P, and K. Addition urea caused nitrogen enriched instraw, especially wheat straw. It is no significant effect to wheat straw and corn strawdecompose when soil water content is16%and20%.