Effects Of Tillage Methods And Exogenous Carbon And Nitrogen On Soil Carbon Composition And Enzyme Activity Of Rice Straw Returning Soil

Northeast China is the main grain production area in China,and a lot of crop straws are produced every year.However,after the rice harvest in autumn,the temperature gradually decreases,the straw C/N ratio is high,the decomposition is slow.In this paper,the effects of returning straw to the field on soil organic carbon components,rice yield,and the effects of exogenous carbon and nitrogen on soil microbial biomass carbon and soil enzyme activity were studied,to explore the relationship between microbial biomass carbon and soil enzyme activity and soil organic carbon components and soil available nutrients,with a view to promoting the decomposition and conversion of rice straw in the Northeast,and providing a reference basis for increasing rice yield.The experiment consisted of two parts:The first part was a field plot experiment to explore the effects of different tillage methods on the soil carbon composition and rice yield.The experiment had four treatments,which were:straw not returned to field+autumn tillage and rotation tillage+water stirring pulp+fishing level(J),straw return to field+autumn tillage and rotation tillage+water stirring pulp+fishing level(SJ),straw return to field+autumn turning and post-rotation tillage+no pulping+fishing level(SP),straw return to field+reverse rotation tillage treatment+no stirring pulp+fishing level(SDP);The second part was the soil incubation experiment,to explore the effects of exogenous carbon and nitrogen on the soil carbon component,soil enzyme activity,and soil available nutrient content of rice straw returned to the field.The test was a completely randomized trial design,2 factors and3 levels,three levels of carbon(T0:0 mg·kg-1,T1:13.34 mg·kg-1,T2:26.68 mg·kg-1),three levels of nitrogen(N0:0 mg·kg-1,N1:26.8 mg·kg-1,N2:53.6 mg·kg-1),a total of nine treatments.The test results were as follows:1.Rice straw was returned to the fields,different village methods could increase the content of soil total organic carbon,water-soluble organic carbon,total humic acid carbon and corbon form free humic acid.After the rice straw was returned to the field,SDP tillage treatment soil total organic carbon,water-soluble organic carbon and rice yield were significantly higher than other treatments;Except SP,the treatment of returning rice straw to the field is higher than that of the treatment without returning J.Rice yield was extremely significant or significantly positively correlated with soil water-soluble organic matter and carbon form free humic acid,and the correlation with total organic matter and total humic acid carbon did not reach a significant level.2.Adding rice straw to the soil combined with exogenous carbon and nitrogen could significantly increase soil microbial biomass carbon,enzyme activity,carbon components and soil available nutrient content.The soil sucrase and cellulase activities reached the highest level after the soil was incubated to the 10th day.The simultaneous addition of carbon and nitrogen treatments could significantly increase soil sucrase activity,and the addition of low nitrogen treatment could significantly increase soil cellulase activity;The soil microbial biomass carbon content and urease activity of each treatment reached the highest on the 30th day of incubation.The addition of high nitrogen treatment could significantly increase soil urease activity,while the addition of high levels of carbon and nitrogen treatment could significantly increase soil microbial biomass carbon content.The contents of total organic carbon,water-soluble organic carbon and total humic acid carbon in the soil were slightly lower than that on the 0th day of incubation.The simultaneous addition of carbon and nitrogen treatment could significantly increase the content of soil water-soluble organic carbon.the content of total organic carbon and total humic acid carbon in the soil treated with exogenous carbon and nitrogen was not significantly different.The contents of soil alkaline nitrogen,available phosphorus and available potassium were all higher than that on the 0th day of incubation.the addition of high nitrogen treatment could significantly increase the soil alkaline nitrogen content,while the addition of carbon and nitrogen treatment could significantly increase the soil available potassium content.The treatment of source carbon and nitrogen showed no significant difference in soil available phosphorus content.Comprehensive field plot experiments and soil cultivation experiments had shown that different tillage methods could increase soil carbon content and rice yield after straw returning to the field;Exogenous carbon and nitrogen could increase the content of soil microbial carbon,enhance the activity of related soil enzymes,accelerate the decomposition of returned rice straw,increase soil organic carbon components and soil nutrient content after returning rice straw to the field.