The Response Of Soil Organic Carbon Stability And Rice Growth To Straw Input

How to increase the organic carbon content in soil to reduce greenhouse gas emissions is currently a hot research topic.The stability of soil organic carbon directly affects the soil’s carbon sequestration ability,so conducting in-depth research on it is of great significance.To clarify the stability of soil organic carbon and the response of rice growth to straw input,this experiment relied on long-term positioning experiments and set up a total of 6 treatments:CK:no fertilization;S0:Conventional fertilization（N:150 kg/hm²,P₂O₅:148 kg/hm²,K₂O:230 kg/hm²）;S1:Conventional fertilization+straw returning to the field 5 kg/hm²;S2:conventional fertilization+straw returning to the field 10 kg/hm²;S3:conventional fertilization+straw returning to the field 15 kg/hm²;S4:Conventional fertilization+straw return to field 20 kg/hm².By combining indoor mineralization cultivation and soil physicochemical grouping methods,the stability of soil organic carbon and the response of rice growth to straw input were revealed.The results indicate that:（1）Straw returning treatment increased soil organic carbon content.Compared with S0 treatment,soil organic carbon in S3 treatment increased significantly by 20.93%（tillering stage）,22.89%（heading stage）,and 22.96%（mature stage）;The soil MBC of S1,S2,and S3 treatments increased significantly by 14.00%,25.20%,and 27.06%,respectively,while the MBC of S4 treatment decreased by 4.36%（P>0.05）.The soil DOC and ROC of S1-S4 treatment increased significantly by 9.79%to 36.78%,and5.19%to 12.16%,respectively.Soil MBC,DOC,and ROC showed a trend of first increasing and then decreasing with the increase of straw returning to the field.（2）Compared to S0 processing.The content of free active organic carbon in soils treated with S2,S3,and S4 increased by 12.61%to 20.24%,with S3 reaching a significant level,while the content of free active organic carbon in soils treated with S1decreased by 0.86%;The content of soil physical protective organic carbon increased by 4.12%to 11.34%under straw returning treatment,with S3 reaching a significant level;The content of soil chemical protective organic carbon significantly increased by2.59%to 18.77%under S3 and S4 treatments;The biochemically protected organic carbon content of each treatment increased by 35.20%to 55.60%,with S2,S3,and S4treatments reaching significant levels;The percentage of free active organic carbon and biochemically protected organic carbon in soil treated with straw returning to the field had no significant impact;The proportion of physically protected organic carbon in S3treatment decreased by 19.57%,while the proportion of chemically protected organic carbon in S3 and S4 treatment increased by 13.16%and 5.35%,respectively,without reaching a significant level（P>0.05）.（3）The mineralization rate of organic carbon is divided into four stages during the incubation period.After the end of incubation,the cumulative mineralization amount and cumulative mineralization rate of organic carbon fluctuate between1023.11～1254.73 mg/kg and 4.50%～6.53%,respectively,with S3 treatment being the lowest,reflecting that straw returning treatment has a low mineralization intensity on soil and is beneficial to soil carbon fixation capacity.（4）The treatment of returning straw to the field has a significant effect on improving soil nutrient content,with S3 treatment having the best effect.During the mature period,the content of alkali hydrolyzed nitrogen,available phosphorus,and available potassium in S3 treatment significantly increased by 18.77%,21.23%,and37.26%compared to S0 treatment,respectively.The straw returning treatment can all improve rice yield,with a significant difference between S2 and S3 treatments,with S3significantly increasing by 6.27%compared to S2 treatment;The straw returning treatment significantly increased the dry weight,root to shoot ratio,and root morphology of rice roots.The root dry weight,root crown ratio,and root morphology of S3 treatment were better than those of S0 treatment.（5）The correlation analysis results show that there is a significant positive correlation between soil organic carbon and free active component organic carbon,physical protective component organic carbon,chemical protective component organic carbon,biochemical component organic carbon,soluble organic carbon,and easily oxidized organic carbon;There is a significant negative correlation with microbial biomass carbon,soil organic carbon mineralization rate,and soil organic carbon mineralization.In summary,conventional fertilization combined with straw returning of 15 t/hm²can significantly increase the content of stable organic carbon components in soil,increase the proportion of chemical protection organic carbon and biochemical organic carbon,reduce soil organic carbon mineralization,promote soil organic carbon stability,and increase rice yield.