Effects Of Straw Return And Fertilizer Reduction On Wheat Yield And Soil Nutrients Of Wheat-maize Rotation Region

Shaanxi province is one of the main agricultural production areas in China.Winter wheat-summer maize rotation is the main crop planting mode in Guanzhong area of Shaanxi province.In order to provide scientific guidance for high yield and high efficiency of wheat and rational utilization of straw in wheat-rotation area of Guanzhong,field experiments were carried out in Zhouzhi County and Wugong Town of Shaanxi province to reveal the effects of straw returning combined with nitrogen fertilizer and fertilizer reduction on wheat yield and soil nutrient.Province to reveal the effects of straw mulching and nitrogen application on wheat yield and soil properties.The long-term experiment was divided into two types: straw returning(N +S)and straw not returning(N)as the main treatment,and different nitrogen level(N0,N84,N168,N225,N336kg/hm2)as side treatments.The fertilizer reduction experiments were conducted on the effects of different fertilization modes on winter wheat yield and soil nutrient.There were five treatments in total: comparison,farmer straw addition treatment,farmer pattern no straw addition treatment,,monitored fertilization,and integrative water and fertilizer.The main results obtained from the experiment are as follows:(1)The long-term experiment showed that the effect of straw returning and nitrogen fertilizer on wheat yield was that the yield of low nitrogen fertilizer decreased and the yield of high nitrogen fertilizer increased.The fertilizer effect curve for 8 consecutive years has an intersection except for 2017.The intersection points of fertilizer effect curve from 2012 to 2016 are 153,187,76.5,99,147 kg N/hm2,and 225 and 201 kg N/hm2 from 2018 to 2019.When N application was lower than the intersection value,the wheat yield in the straw-returned treatment was lower than that in the no-return treatment,the yield in the straw-returned treatment was higher than that in the no-return treatment,and the yield in the straw-returned treatment was higher than that in the no-return treatment.(2)In the long-term positioning test,straw returning to the field and nitrogen application mainly affect the yield by affecting the number of ears of wheat.Straw addition treatment can increase the number of spike number of winter wheat.Only in 2015,the number of spike number under straw returning treatment significantly increased by 11.8% compared with that under no return treatment.In other years,the increase range was 0.5%-9.3%,but no obvious difference.The number of ears of winter wheat increased first and then decreased with the increase of N application,which was consistent with the change trend of wheat yield with N application.The straw returning has no significant influence on the grain number per ear and 1000-grain weight of winter wheat,and 1000-grain weight tends to decrease with the increase of nitrogen application.(3)Under the same N level,straw returning had no significant effect on the N,P and K content of wheat grain,but it increased with the increase of N application amount,which increased by 3.6-40.7% and 8.1%-45.7% in 2018-2019 compared with the treatment without N application.Compared with maize straw that was not returned to the field,the nitrogen absorption of wheat above-ground increased by 40.1%-108.7% and 70.2%-142.6%,respectively,in the two growing seasons.The N harvest index of straw returning increased at low nitrogen application rate and had no difference at high nitrogen application rate.The partial productivity of nitrogen application decreased significantly with the increase of nitrogen application rate,and straw returning to the field had little influence on it.The nitrogen utilization efficiency decreased with the increase of nitrogen application,and the nitrogen utilization efficiency of straw mulching treatment increased by 0.9 % to 44.7 % from 2012 to 2019 compared with that of non-straw mulching treatment.(4)With the increase of the straw returning period,the organic matter content in the soil showed an increasing trend.Under the same nitrogen application amount,the soil organic matter content in the straw returning treatment was higher than that in the no-return treatment.From 2012 to 2019,the soil organic matter content in 0-20 cm soil straw returning treatment increased by 6.24 % compared with that in the no-return treatment.After the straw was returned to the field in the same year,the nitrate nitrogen content,the available phosphorus content and the available potassium content in the 0-20 cm soil layer were all higher in the straw returned to the field.With the increase of years,the nitrate nitrogen content of soil will move down with the soil layer.Soil nitrate nitrogen,available phosphorus and available potassium are easily affected by fertilization,water content,climate and other factors,so they do not show a trend of increasing year by year.Soil nitrate nitrogen,available phosphorus and available potassium are easily affected by fertilization,water content,climate and other factors,so they do not show a trend of increasing year by year.(5)The fertilizer reduction test showed that,compared with the control,the grain yield of winter wheat was significantly increased under several different modes.Among them,the yield of winter wheat under the integrated water and fertilizer mode was the highest,with an increase of 20% compared with the control,8.7 % higher than the monitored fertilization and 5.3 % higher than the peasant household mode.Several different patterns mainly affect the crop yield by influencing the number of ear and grain per ear of winter wheat.Compared with the control group,the content of available p and K in the soil in the peasant model increased significantly by 77 % and 35 %.In a word,when straw was returned and nitrogen fertilizer was applied,the microbial decomposition of straw consumed part of nitrogen at low nitrogen level,which affected the growth of winter wheat.With the increase of nitrogen application,the positive effect of straw returning to the field gradually showed.The contents of Soil organic matter,nitrate nitrogen,available P,available K were increased by long-term mulching straw.Organic matter,nitrate nitrogen,available P,and available K increase 6.24 %,20.45 %,3.9 % and 11.2 %.The integration of water and fertilizer can reduce the amount of nitrogen fertilizer,improve the efficiency of fertilizer and increase the yield of wheat significantly.