| Green development is the basic requirement of modern agricultural development,and greenhouse gas emissions are one of the main factors that cause a series of ecological and environmental problems such as global warming.Therefore,in order to achieve green agricultural development,it is very important to carry out research on green greenhouse gas emission reduction.Based on the winter wheat-summer maize rotation mode in Guanzhong Plain,the experimental design of the split area was adopted,and the main treatment was set to different straw return modes:straw non-return（W0）,straw return（W1）,and the secondary treatment was set to different fertilization modes:no fertilization（/）,nitrogen fertilization（N）,nitrogen and phosphorus fertilizer（NP）.The effects of straw returning with chemical fertilizer on farmland hydrothermal status,nutrient content changes and N2O emissions were studied,and the correlation between soil hydrothermal conditions and nutrient changes and farmland N2O emissions was analyzed,and the following results were obtained:（1）Straw return measures have a certain moisture preservation effect on farmland,which can significantly increase the moisture content of soil by 0-10 cm.When the nitrogen fertilizer was applied at N 225 kg·hm-2,the straw return measures could increase the soil organic carbon and total nitrogen content（P<0.05）in the winter wheat season compared with the straw not returned to the field,and the effect on promoting soil microbial activity was obvious.When the amount of nitrogen and phosphorus fertilizer was applied at N 225 kg·hm-2+P2O5140 kg·hm-2,the straw return measures could significantly increase the content of soil microbial biomass carbon,nitrogen and phosphorus,as well as soluble organic carbon and nitrogen（P<0.05）compared with straw not returned to the field.For farmland N2O emissions,under the background of single application of nitrogen fertilizer(N225 kg·hm-2)and nitrogen and phosphorus fertilizer(N 225 kg·hm-2+P2O5 140 kg·hm-2),the cumulative emission and emission intensity of farmland were enhanced by straw return,but the impact of short-term return on yield was not significant（P>0.05）.（2）When the nitrogen fertilizer was applied at N 225 kg·hm-2,the nitrogen fertilization measures significantly increased the soil total nitrogen,microbial carbon nitrogen,and soluble nitrogen content（P<0.05）compared with no nitrogen fertilizer,and greatly increased the soil inorganic nitrogen content in a short period of time,of which the nitrate nitrogen content in the soil was linearly positively correlated with the N2O emission flux of farmland,and compared with no nitrogen fertilizer,the cumulative N2O emission,emission intensity and yield of farmland were significantly improved（P<0.05）.（3）When the amount of nitrogen and phosphorus fertilizer was applied N 225 kg·hm-2+P2O5 140 kg·hm-2,compared with the nitrogen fertilizer treatment without phosphorus fertilizer and only nitrogen fertilizer,the nitrogen fertilizer combined with phosphorus fertilizer measures significantly increased the soil total phosphorus,total nitrogen and microbial carbon nitrogen and phosphorus,as well as soluble carbon and nitrogen and available phosphorus（P<0.05）,and the cumulative emission intensity of N2O emissions of farmland treated with nitrogen and phosphorus fertilizer treatment was significantly lower than that of nitrogen fertilizer treatment only（P<0.05）;and the application of phosphorus fertilizer significantly improved crop yield（P<0.05）.In summary,in the wheat-maize rotation field in Guanzhong area,straw returning can effectively improve soil microbial activity,and the slow decomposition can be used as soil organic carbon and nitrogen source for a long time.The combined application of nitrogen fertilizer under straw returning should reduce nitrogen and fertilize on the basis of ensuring yield;and it needs to be combined with an appropriate amount of phosphorus fertilizer to increase yield and reduce N2O emissions from farmland accordingly. |
