Effects Of Straw Returning And Chemical Fertilizer Reduction On Winter Wheat Yield And Soil Nutrients

As one of the main grain production areas in China,winter wheat-summer maize rotation is the main planting mode in Guanzhong Plain of Shaanxi Province,and straw returning is the main utilization mode of local straw resources.In order to provide a scientific basis for rational management of nitrogen fertilizer under the condition of straw returning,stable crop yield and reduction of soil nitrate nitrogen residue and leaching,field location experiments were carried out in Zhouzhi County and Wugong County in Guanzhong Plain.Of zhouzhi county Wang Caitun village field location experiment using split block design,the main treatments included maize straw returning to soil and removal straw from field,the subplots included five N application rate,i.e.,0（N0）,84 kg hm^-2（N84,low nitrogen fertilizer）,168 kg hm^-2（N168,local recommended nitrogen fertilizer）,252 kg hm^-2（N252,high nitrogen fertilizer）,and 336kg hm^-2（N336,super high nitrogen fertilizer）,a total of 10 treatments.The effects of straw returning and nitrogen application on winter wheat yield and nitrogen uptake and utilization under wheat-maize rotation system were studied.Wu gong county Gu Feng village field experiment set up seven treatments:farmer mode no straw addition treatment,farmer mode,monitoring fertilization mode,monitoring nitrogen reduction mode,monitoring phosphorus reduction mode,monitoring potassium reduction mode,integration of water and fertilizer mode on winter wheat yield reduction is studied to explore the effects of chemical fertilizer reduction on winter wheat yield and soil nutrients.The main conclusions of the experiment are as follows:1、The results of location-fixed field experiment showed that compared with no straw returning,straw returning did not significantly increase the grain yield of winter wheat,but straw returning combined with nitrogen fertilizer could increase grain yield.Nitrogen application rate significantly increased wheat yield.Compared with N0,the yield increases of N84,N168,N252 and N336 were 18%,24%,29%and 24%,respectively.However,there is a risk of yield reduction due to high N application rate.Straw returning and nitrogen application rate had interaction effect on wheat yield.Compared with no straw returning,straw returning yielded an average yield of 5%-6%at 252 kg N hm^-2 and 336 kg N hm^-2,which was mainly due to a 5%-7%increase in the number of panicle per hectare.2、The results of location-fixed field experiment showed that straw returning had no significant effect on grain protein content and aboveground nitrogen uptake under the same nitrogen application level.No matter whether straw was returned to the field or not,increasing nitrogen application rate significantly increased grain protein content and aboveground nitrogen uptake.Compared with N0,nitrogen application increased grain protein content by16%-33%,and aboveground nitrogen uptake by 36%-72%.The interaction between straw returning and nitrogen application rate had a significant effect on aboveground nitrogen uptake.Straw returning and increasing the amount of nitrogen fertilizer significantly increased soil nitrate nitrogen residue.Under the conditions of N0,N84,N168,N252 and N336,soil nitrate nitrogen residue increased by 30%,7%,29%,20%and 13%on average,respectively,when straw was returned.Compared with N0,soil nitrate nitrogen residues in N84,N168,N252 and N336 were increased by 73%,327%,610%and 881%,respectively.Straw returning can increase the NO₃^--N content in deep soil under high N application rate.Under the same nitrogen application level,the nitrogen surplus of soil was significantly increased by straw returning to the field compared with that of no straw returning.3、Compared with no straw returning,the contents of soil organic matter,available phosphorus and rapidly available potassium under the straw returning condition did not reach significant differences,but the contents of soil organic matter,available phosphorus and rapidly available potassium showed an increasing trend.Similarly,the contents of soil organic matter,available phosphorus and rapidly available potassium increased with the increase of nitrogen application.4、Wu gong county fertilizer reduction,according to the results of field experiments compared with the nitrogen reduce mode,phosphorus reduce mode,potassium reduce mode,farmer mode no straw addition treatment,farmer mode,monitoring fertilization mode,integration of water and fertilizer mode were significantly increased the yield of winter wheat.The highest yield of winter wheat was 8091 kg hm^-2 in the integration of water and fertilizer mode.Compared with the farmer mode no straw addition treatment,the winter wheat yield in the farmer mode increased by 3.2%.Compared with the farmer mode,the integration of water and fertilizer mode reduced nitrogen use by 50%,but the winter wheat yield increased by 12%.Nitrogen use was reduced by 40%and winter wheat yield increased by 19%in the integration of water and fertilizer mode compared to the monitoring fertilization mode.According to the analysis of yield components,the increase of the number of spike is the main reason for the increase of winter wheat yield.Compared with the N,P and K reduce modes,farmer mode no straw addition treatment,farmer mode,monitoring fertilization mode,integration of water and fertilizer mode all increased the contents of NO₃^--N,organic matter,available P and available K in 0-20 cm soil layer.Among them,soil nitrate N,organic matter,available P and available K contents in 0-20 cm soil layer were the highest under the farmer mode.