Effects Of Biochar Addition On Black Soil Aggregates And Soil Organic Carbon Composition In Greenhouse Vegetable Field

In recent years,one of the precious soil resources in China,the black soil in Northeast China,has been severely degraded.Specifically,it manifests as a significant loss of soil organic matter,significant nutrient imbalance,and continuous decline in fertility.Biochar can improve soil quality to a certain extent,but the improvement effect on soil quality in different soil layers is still unclear.In order to explore the impact of biochar addition on total organic carbon and nitrogen,active organic carbon components and aggregates in different soil layers of black soil,we took the black soil of protected vegetable fields in Northeast China as the research object,and adopted three treatment methods: conventional water fertilizer(WF),conventional water fertilizer and biochar(WFB),80% water 80% fertilizer and biochar(80%W80%FB).The wet screening method was used to determine the content of aggregates in various particle sizes of the 0-100 cm soil layer,as well as the content of organic carbon,nitrogen,and organic carbon components in the soil and aggregates.The distribution characteristics of soil organic carbon and nitrogen,organic carbon components,aggregates,and aggregate organic carbon and nitrogen were systematically analyzed.The results indicate that:(1)From the distribution of soil organic carbon and nitrogen,compared with WF,WFB and 80% W80% FB treatments showed a marked increase in the content of soil total organic carbon(TOC)and total nitrogen(TN)in 0-20 cm soil layer(p<0.05),with increases of 16.50% and 20.98% for WFB,56.05% and 47.30% for 80%W80%FB.The TOC content in the 20-100 cm soil layer was significantly reduced(p<0.05),with a reduction range of 19.48%-37.19% and 9.68%-19.15%.The analysis of soil organic carbon composition showed that compared with WF,WFB treatment increased the content of particulate organic carbon(POC),easily oxidizable organic carbon(ROC),light organic carbon(LFOC),biochar(MBC),and soluble organic carbon(DOC)in each soil layer,with increases of 16.86%-89.23%,13.37%-64.32%,11.46%-29.24%,8.95%-32.45%,and 8.70%-44.73%.80%W80%FB treatment increased the MBC content in each soil layer,with an increase of 4.90%-13.28%;The LFOC content in each soil layer was reduced by 10.40%-15.81%.(2)From the distribution characteristics of aggregates,compared with WF,WFB marked reduce the content of large aggregates in the 0-20 cm soil layer,with a decrease of 16.74%.The aggregate stability also showed a significant decrease;Significantly increased the content and stability of soil macroaggregates in the 20-100 cm soil layer,with an increase in macroaggregate content ranging from 7.83% to 23.85%.Under80%W80%FB treatment,the content of large aggregates significantly increased by18.58% and 4.78% in soil layers of 20-40 cm and 40-60 cm.The aggregate stability was significantly improved in the 0-60 cm soil layer.Compared with WF,WFB and80%W80%FB treatments significantly increased the TOC content of various particle size aggregates in the 0-20 cm soil layer(p<0.05),with an increase of 39.40% to 129.29%and 18.78% to 130.19%.Significantly increased the TN content of other particle size aggregates except for those >5mm(p<0.05),with an increase of 6.68% to 79.89% and29.63% to 100.00%.(3)Correlation analysis showed that TOC and TN showed a significant positive correlation with 5 organic carbon components,and a significant positive correlation with the content of TOC and TN in 6 particle size aggregates.The average weight diameter,geometric weight diameter,and the content of aggregates in particle sizes of >0.25 mm are significantly negatively correlated with the TOC and TN content of six particle size aggregates,while they are significantly positively correlated with the content of particle size aggregates of >5mm,5-2mm,and 2-1 mm.The analysis of eggplant yield showed that compared with WF,WFB and 80%W80%FB treatments increased eggplant yield by 20.45% and 31.08%(p<0.05).In summary,while ensuring eggplant yield,80% W80% FB can more promote the accumulation of TOC,TN,and aggregate particle size content in each layer of soil,which is more conducive to improving the aggregate stability of 0-60 cm laye.