Effect Studies On Increasing Soil Fertility And Carbon Sequestration Of Rice Straw Return With Mud In Autumn

Carelessly discarded rice straw is not only the wasted resources,but it is also a risk source of environmental pollution.Meanwhile,organic material input of farmland is insufficient,and soil organic matter decreased.Rice straw return is an effective way to solve this question.Rice straw return with mud in autumn has been carried out in northeast China,but the effect mechanism of this measure is not clear on soil fertility,carbon sequestration and emission reduction.So,it has very important theoretical significance and practical value to carry out relevant researches for promoting straw resource utilization and realizing green development of rice production.The research methods in this paper are field investigation,indoor analysis and simulation calculation.In this paper,the effects of rice straw return with mud in autumn for 8consecutive years on soil fertility,carbon sequestration and comprehensive benefits of rice production were studied.These studies revealed the change of soil fertility and the characteristics of emission reduction and carbon sequestration under long-term rice straw returning mode,and provided theoretical basis and technical reference for promoting rice straw returning technology.The main conclusions are as follows:1.The contents of soil organic carbon and available potassium,soil fertility and the composition of soil organic carbon were all improved by rice straw return with mud in autumn.Compared to the conventional farming,the content of soil organic carbon in 0-40cm layer was significantly increased by 11.3%（p<0.05）.Soil microbial biomass carbon（p<0.01）,light organic carbon（p<0.01）and free particulate organic carbon content（p<0.01）were significantly increased in 0-20 cm and 20-40 cm soil,and the increase rates were 65.3%,18%,29%and 70.8%,99.6%,141%,respectively.Soil p H（p<0.05）and soil available potassium content（p<0.01）in 0-20cm and 20-40cm depth were significantly increased by5.4%,2.2%and 38.1%,54.9%,respectively.2.Rice straw return with mud in autumn not only enhanced the capacity of emission reduction and carbon sequestration,but also improved soil organic carbon storage.At the same time,it reduced indirect carbon emissions and the use of fertilizers and pesticides.The carbon sequestration effect of long-term rice straw return with mud in autumn is greater than the global warming risk caused by CH₄emission.Compared with conventional tillage,rice straw return with mud in autumn increased soil organic carbon storage by 18.8 t CO₂-eq/hm²in 0-40 cm layer,and reducing fertilizer and pesticide application reduced indirect carbon emission by 3.34 t CO₂-eq/hm².There was a significant carbon sequestration effect after continuous rice straw returning for 12 years considering the life cycle of CH₄.3.The comprehensive benefit of rice production was improvedby rice straw return with mud in autumn.Compared with conventional tillage,the net income of rice straw return with mud in autumn increased by 40%.At the same time,the potential environmental risk from fertilizer and pesticide using are reduced,and that avoids the social problems caused by the reduction of air quality which caused by the incineration of rice straw.In conclusion,the mode of rice straw return with mud in autumn can improve soil fertility,and enhance the ability of rice production,emission reduction and carbon sequestration.So,this mode has better comprehensive benefit and is suitable for promotion and development in Panjin area..