Effects Of Straw And Biochar On Carbon Sequestration,Distribution And Greenhouse Gas Emissions In Paddy Fields

Research on global warming and carbon sequestration and emission reduction in ecosystems has become a hot research topic.The paddy field ecosystem has a high potential for carbon sequestration,which is of great significance for ensuring food security and achieving the goal of carbon neutrality by 2060.In this context,it is very important to explore fertilizer reduction technologies while reducing greenhouse gas emissions and increasing crop yield.Based on this,this study took the paddy field of Wufeng Comprehensive Experimental Base of Rice Research Institute of Fujian Academy of Agricultural Sciences as the research object,and set up four treatments:control,straw,biochar,and silicon-rich biochar.Through in-situ measurements in the field and indoor analysis,with the help of techniques such as isotope and molecular biology,we have studied and revealed the effects of straw and its biochar on carbon sequestration,distribution and greenhouse gas emissions in paddy fields.The main research conclusions are as follows:（1）Straw,biochar and silicon-rich biochar treatments significantly increased leaf TC content（P<0.05）;Straw treatment decreased the carbon sequestration of paddy fields,while the biochar and silicon-rich biochar treatments both increased the carbon sequestration of paddy fields,and significantly increased the carbon sequestration of rice stems,leaves and grains（P<0.05）.Straw treatment decreased paddy yield and net primary productivity,while biochar and silicon-rich biochar treatments significantly increased paddy yield and net primary productivity（P<0.05）.Overall,the net primary productivity of straw and biochar treatments were significantly higher than that of early paddy during late paddy（P<0.05）.（2）The application of straw and biochar significantly increased the SOC content of paddy soil,and significantly increased the LOC content of 15-30 cm soil layer（P<0.05）.Although the content of soil DOC and MBC was increased,the difference between the treatments was not significant.The content of carbon components in the 0-15 cm soil layer was higher than that in the 15-30 cm soil layer at the same period,and there was a big difference between the early and late paddy and the fallow period.Overall,each treatment improved the soil carbon pool management index in the paddy period.Each treatment affect soil nutrient content and environmental factors,thereby affecting soil carbon components.The contribution rate of soil nutrient content and its environmental factors to the various indicators of soil carbon components in descending order was AP（19.90%）>NO₃^--N（9.70%）>ST（7.30%）>TP（4.10%）>TN（1.90%）>p H（1.50%）.（3）The percentage content of aggregates in each treatment was mainly<0.25 mm grain size.The straw and biochar treatments reduced the content of microaggregates（<0.25mm）in paddy fields;macroaggregates（>0.25 mm）carbon content is higher than the carbon content of microaggregates.The soil aggregate carbon content of the plow layer（0-15 cm）is higher than that of the plow layer（15-30 cm）in the same period.Compared with the control,the treatments of straw,biochar and silicon-rich biochar all increased the carbon content of aggregates of each grain size in the paddy soil;the treatment of straw and biochar increased the MWD and GMD index,decreased the D index,and improved the stability of soil aggregates as a whole.（4）The content of Fe（Al）-SOC in the paddy soil was significantly higher than the content of Ca-SOC（P<0.05）,and the application of straw and biochar treatment increased the content of Fe（Al）-SOC and residue-SOC in the paddy field,but the influence of soil Ca-SOC content was fluctuating.There was a positive correlation between soil bonded organic carbon and soil SOC,indicating that the application of straw and biochar improved the chemical stability of paddy field SOC.Overall,the absorption intensity of the soil absorption peak in the 0-15 cm soil layer of the paddy field in each treatment was higher than that of the control treatment,which increased the content of some aliphatic,aromatic,organosilicon compounds,carboxyl groups,alkanes and other substances,and increased the chemical stability of soil SOC.（5）Straw and its biochar changed the unique OTU number and community composition of fungi and bacteria in the soil,and the number of effective OTUs in the bacterial community was significantly higher than that in the fungal community in each treatment.Both biochar and silicon-rich biochar treatments reduced the diversity of the soil fungal community in late paddy.Both the straw and silicon-rich biochar treatments reduced the diversity and richness of the soil bacterial community in early and late paddy.The changes in nutrient content and availability caused by straw and its biochar treatment would affect the metabolism of soil microorganisms,which in turn affected the function and carbon pool stability of the entire rice field ecosystem.（6）Theδ¹³C_SOC value of the 0-15 cm soil layer soil of each treatment was significantly lower than that of the 15-30 cm soil layer in the same period（P<0.05）.All treatments increased theδ¹³C_SOC andδ¹³C_DOC values of the same soil layer,the straw treatment significantly increased theδ¹³C_SOC value of the paddy field,and the silicon-rich biochar treatment significantly increased theδ¹³C_DOC value in the 15-30 cm layer of paddy fields（P<0.05）.The proportions of SOC derived from straw,biochar and silicon-rich biochar were 11.04～12.04%,6.80～11.10%and 7.19～10.77%,respectively.The proportions of DOC derived from straw,biochar and silicon-rich biochar were 1.60～3.69%,1.03～5.43%and 6.45～8.56%,respectively.（7）The application of straw and its biochar had increased the CO₂ emission level of paddy fields to a certain extent.Straw treatment can significantly increase the CH₄ emission level of paddy fields（P<0.05）.Biochar treatment increased the N₂O emission from early and late paddy（P<0.05）,and reduced the N₂O emission during the fallow period.The treatment of straw and its biochar improved the comprehensive warming effect of early and late paddy.Straw treatment significantly increased the greenhouse gas emission intensity of early and late paddy by 103.04%and 114.85%respectively（P<0.05）;biochar treatment both reduced the greenhouse gas emission intensity of early and late paddy by 1.97%and15.42%,respectively.In conclusion,this study provides theoretical and practical guidance for the field application of straw and its biochar in Fuzhou.Although straw treatment can increase soil SOC content,which is beneficial to soil carbon pool stability,it also increases the greenhouse gas emissions of paddy fields and reduced rice yields.The treatment of biochar and silicon-rich biochar not only improved the yield of paddy field,but also increased the stability of soil carbon pool,which can be further studied in the future.