The Effects Of Straw And Biochar On Soil Organic Carbon Pools And Soil Bacterial Community In Degraded Black Soil

At present,the high-intensity use of land resources and unreasonable management is one of the major factors leading to soil degradation.Soil degradation leads to the decline of soil production capacity,the decline of soil ecological function and environmental capacity.Soil degradation has become one of the main threats to food security and agricultural production.Due to large-scale reclamation and long-term high-intensity cultivation,the soil fertility of the black soil in Northeast China is decreasing year by year.The content of soil organic matter,the physical and chemical properties of the soil declined significantly,the soil structure and the diversity of soil microorganism are seriously degraded,and the black soil in Northeast China has gradually become the area with weak ecological function,which has a serious impact The sustainable development of agriculture in Northeast China.The northeast black soil area is the most important food production area in China.It is an urgent task to protect the black land,preventing the black land from degradation and repairing the degraded black land.Therefore,our country puts forward “the plan of the northeast black land protection”,which clearly points out the importance and urgency of the black land protection.In view of the current situation and problems of the black land,we are encouraged to explore and study the technical measures of the black land protection.Straw and biochar are two very important ways to restore degraded soil.At present,the research focuses on the effects of straw or biochar on the dynamic changes of soil nutrients,the prediction and evaluation of the changes of soil carbon pool by straw or biochar,and the effects of straw or biochar on soil microbial community.However,what are the effects of straw and biochar on different degraded soils? The effects of straw and biochar on the components of organic carbon pool,the relationship between the components of organic carbon pool and soil microbial community are rarely reported in the current research.In this study,two degraded black soils were added with 0.5%,1.5%,2.5% straw or 0.5%,1.5%,2.5% biochar respectively.The main contents of this study are as follows:(1)the effect of straw and biochar on the components of two degraded black soils active organic carbon pool and inert organic carbon pool,(2)the effect of straw and biochar on the mineralization of two degraded black soils organic carbon,(3)the effect of straw and biochar on the physical and chemical properties of two degraded black soils,(4)the effect of straw and biochar on the bacterial community of two degraded black soils,and the relationship between the components of carbon pool and soil physical and chemical properties and bacterial community.It provides theoretical basis for the restoration of degraded black soil with different organic matter content and the rational and scientific application of straw and biochar.The results are as follows:(1)The addition of straw can significantly increase the content of soil active organic carbon,and there is a significant positive correlation between soil easily oxidized organic carbon(EOC),dissolved organic carbon(DOC),microbial biomass carbon(MBC),particulate organic carbon(POC)(P < 0.05).Among all treatments,the treatment with 2.5% straw had the highest content of soil active organic carbon.The addition of straw had no significant effect on the components of soil inert organic carbon pool.(2)The addition of biochar had no significant effect on soil EOC and soil DOC,but biochar significantly increased soil POC content.The addition of biochar significantly increased the content of soil inert organic carbon,and there was a significant positive correlation between t oil recalcitrant organic carbon(ROC)and soil mineral incorporated organic carbon(MOC)(P < 0.05).The content of soil inert organic carbon pool was the highest when biochar content was 2.5%.(3)Straw application can significantly increase soil carbon pool management index(CPMI)in two soils,while biochar has no significant effect on the two soil CPMI,which shows that straw can increase soil activity.We further studied the contribution of soil organic carbon pool components to total organic carbon(TOC)by stepwise regression analysis.We found that biochar increased soil TOC mainly by increasing the content of ROC in the soil,and straw increased soil TOC mainly by increasing soil POC.It was found that the mineralization rate of straw in both soils was very high,up to 74.40%,while the mineralization rate of biochar was very low.The release and accumulation of CO2 from straw is 2.31-6.12 times that of biochar.(4)Straw and biochar had no significant effect on total nitrogen,total phosphorus and total potassium,but straw and biochar could significantly increase soil available potassium,straw and biochar could significantly reduce soil bulk density.Biochar can significantly increase the p H value of soil,while straw can increase the content of soil available nitrogen to a certain extent.(5)Through Q-PCR quantitative amplification of bacterial genes in two soil samples,it was found that the application of straw could significantly increase the bacterial abundance of soil,while the bacterial abundance of biochar treatment was not significantly different from the control.Furthermore,we found that the relative abundance of Actinobacteria and Gemmatimondetes increased with the increase of straw addition,while that of Bacteroidetes and Chloroflexi decreased with the increase of straw addition.The relative abundance of Acidobacteria decreased slightly with the addition of biochar.We also found that the addition of straw significantly changed Shannon and Simpson diversity index.(6)We studied the effects of straw and biochar on the structure of soil bacterial community,as well as the relationship between the components of carbon pool,physical and chemical properties and bacterial community by Principal coordinate analysis,No-metric multi-dimensional scaling analysis and Canonical correspondence analysis.The results showed that the bacterial community of high organic soil and low organic soil was divided into two parts,and the addition of straw and biochar had a significant impact on the distribution of bacterial community structure,and the difference between the communities in each area was very significant(r = 0.5012,P < 0.001).Mantel test showed that there was a significant correlation between soil bacterial community and soil active organic carbon pool,including EOC(r = 0.286,P = 0.001),Doc(r = 0.174,P = 0.002)and MBC(r = 0.295,P = 0.001).These results show that the components of the active organic carbon pool are the key factors affecting the bacterial community structure of degraded soil.There was a significant correlation between soil bacterial community and p H value(r = 0.241,P = 0.002),which indicated that adding biochar could affect soil bacterial community structure by changing soil p H.All in all,straw is better than biochar in improving soil active organic carbon pool and soil bacterial community.Biochar was better than straw in increasing soil inert organic carbon pool,increasing soil carbon storage and reducing soil mineralization.For the soils with serious organic matter decline,it is suggested that not only straw should be added to improve the soil active carbon pool,but also biochar should be added to increase the soil inert carbon pool;for the soils with high organic matter,increasing biochar appropriately is conducive to soil carbon storage,and excessive application of straw or biochar will produce excitation effect and promote mineralization.