Effects Of Straw Returning And Nitrogen Fertilizer Application On Soil Water And Heat In Summer Maize Farmland And Optimization Of Water And Nitrogen Tilization

Facing the problems of waste of agricultural resources,environmental pollution and climate change arising from the progress of science and technology and the development of society,reasonable farmland management measures should be formulated to improve the efficiency of resource utilization and achieve the goal of stable production and emission reduction.Therefore,this study clarified the effects of different production conditions on soil ammonia volatilization under straw returning conditions through Meta analysis,and analyzed the effects of different nitrogen fertilizer types and different straw returning modes on soil moisture,temperature,crop yield,soil ammonia emissions,water and nitrogen use efficiency content through field experiments.Using the experimental data to calibrate the parameters of the DNDC model,comprehensively considering the yield,ammonia emission and water and nitrogen use efficiency of maize per unit of production,the fertilization-straw measures suitable for future climatic conditions were screened to achieve the goal of high yield and emission reduction in Guanzhong area and improved water and nitrogen use efficiency.The experiment adopted a completely randomized block design,and set two factors:nitrogen fertilizer type and straw returning mode.The types of nitrogen fertilizers included the application of stable nitrogen fertilizer F1(180 kg·hm^-2)and urea F2(180kg·hm^-2);the straw returning mode was set to two levels,including non-returning straw（N）and total straw return field（S）,a total of 4 treatments.The conclusions and results of this study are as follows:（1）The results of Meta analysis showed that the reduction effect of straw returning on soil ammonia volatilization weakened with the increase of cumulative precipitation during the growth period,and increased with the increase of the average temperature during the growth period and soil clay content,with the increase of nitrogen application rate,it showed a trend of first weakening and then increasing.Straw returning to the field by ploughing or rotary tillage can significantly inhibit the volatilization of soil ammonia.In paddy fields,the average temperature and accumulation of rainfall during the growth period were the main factor affecting soil ammonia volatilization under straw returning conditions;in non-paddy fields,nitrogen application rate was the main factor affecting soil ammonia volatilization under straw returning conditions.（2）Straw returning to the field had the effect of regulating temperature and water retention on farmland soil,and the effect was obvious in the early stage of growth.Straw returning could significantly increase summer maize yield by 4.96%-9.41%,water use efficiency by 5.02%-12.70%,and nitrogen partial productivity by 4.96%-9.41%（P<0.05）.Under the same straw returning mode,the application of different types of nitrogen fertilizers had no significant effect on the yield of summer maize,but the application of stable nitrogen fertilizers reduced the accumulation of ammonia volatilization in the whole growth period by 84.10%-87.28%.（3）Using the parameter-corrected DNDC model to simulate soil temperature,soil moisture,yield and soil ammonia volatilization accumulation in 2019 and 2020 and compare them with the actual observed values,R²was 0.51-0.99,n RMSE was5.57%-30.7%,indicating that the simulated values were basically consistent.Under the future RCP4.5 and RCP8.5 emission scenarios,the average annual temperature and annual precipitation both showed an upward trend.Under the two emission scenarios,the future yield of straw returning and stable nitrogen fertilizer application would be significantly higher than the current one,and the accumulated amount of soil ammonia volatilization would be significantly lower than the current one.（4）The corrected DNDC model was used to simulate the summer maize yield,soil ammonia volatilization accumulation,water use efficiency and nitrogen partial productivity under different fertilization-straw measures scenarios.The results showed that:under future climatic conditions,straw returning can improve summer maize yield and water and nitrogen use efficiency and reduce soil ammonia volatilization accumulation per unit yield.Under the RCP4.5 emission scenario,the full amount of straw returned to the field and the application of 180 kg·hm^-2stable nitrogen fertilizer yield and water and nitrogen use efficiency were higher,and the soil ammonia volatilization accumulation per unit yield was lower;under the RCP8.5 emission scenario,from 2030s to 2050s,the full amount of straw was returned to the field with 180 kg·hm^-2stable nitrogen fertilizer yield and water and nitrogen use efficiency,and the soil ammonia volatilization per unit yield was lower,from2070s to 2090s,the full amount of straw was returned to the field with 162 kg·hm^-2stable nitrogen fertilizer yield and water and nitrogen use efficiency,and the soil ammonia volatilization per unit yield was lowerIn conclusion,straw returning has a positive effect on summer maize yield and water and nitrogen use efficiency,and has the effect of maintaining soil moisture and temperature,and stable nitrogen fertilizer has a better emission reduction effect than conventional urea.Under the RCP4.5 emission scenario,returning the full amount of straw to the field and applying 180 kg·hm^-2stable nitrogen fertilizer is the optimal fertilization-straw measure in the future 2030s-2090s;under the RCP8.5 emission scenario,the combination of 180kg·hm^-2stable nitrogen fertilizer with full straw returning and 162 kg·hm^-2stable nitrogen fertilizer with full straw returning to the field is the optimal fertilization-straw measures in the future 2030s～2050s and 2070s-2090s,respectively.