Effects Of Straw Returning On Soil Nitrogen Transformation Characteristics In Winter Wheat-summer Maize

China is a big agricultural country.A large number of straw will be produced every year in agricultural production.If the straw is not used reasonably,it will cause serious ecological environment load.The adverse consequences of these straw will not only affect the nutrient cycle of soil in the field,but also be called the source of various kinds of pollution.In the various ways of utilizing straw,it is the simplest and most effective way to return straw to wheat and corn.It is not only an important agricultural science problem,but also the practice of agricultural production to realize the rationalization of farmland straw,to realize the utilization of straw resource and to improve the quality of cultivated land.Nitrogen elements in soil are one of the main limiting elements for crop growth,but nitrogen in soil and straw mainly exists in organic form.However,organic nitrogen can only be mineralized and converted to inorganic nitrogen（such as nitrate nitrogen and ammonia nitrogen）to provide nutrients for crop growth and be absorbed and utilized.Therefore,it is necessary to study the conditions of winter wheat tillage mode in North China-Winter Wheat-summer maize rotation and the effect of straw returning to soil nitrogen transformation characteristics,which is beneficial to better understanding the nitrogen chemical transformation mechanism of crop straw returning to the field.In this study,the effect of straw returning to soil nitrogen transformation characteristics was studied with field and laboratory experiments.It was found that the total nitrogen content in the soil was increased with the increase of nitrogen content in the soil.The content of soil microbial nitrogen increased with the increase of straw returning and nitrogen application.In addition,the study also found that crop straw returning can promote nitrogen transformation in soil,indicating that the non mineral nitrogen in the soil can be converted;both straw and nitrogen fertilizer alone or mixed in the short term have significant effects on the soil nitrate nitrogen,and the amount of nitrogen is applied to the farmland soil.Fertilizer will increase N₂O emissions,and crop straw returning to soil can reduce soil N₂O emissions;after the harvest of wheat harvest,the yield and yield components of wheat are compared,and it is found that straw returning to wheat and corn yield has a favorable effect.To sum up,straw returning has a favorable effect on soil nutrient and crop yield in the mode of winter wheat and summer corn rotation in North China,which promotes the mineralization of soil nitrogen,reduces N₂O emission and increases crop yield.But compared with straw returning alone,if nitrogen fertilizer is applied to field,it can provide mineral nitrogen for crops better.