| As one of the main soil types in Northeast China,black soil has been used for many years to reduce the organic carbon in black soil and decrease soil fertility because of the unreasonable agricultural planting methods and management measures.Corn is the main grain crop in Northeast China.Every year,a large number of straw has not been effectively used and turned into agricultural waste,even as fuel to pollute the atmosphere.Straw crushing and returning to field as a simple conservation tillage measure is conducive to improving soil organic carbon content and improving soil fertility.In recent years,the impact of straw returning on soil carbon pool has become a hot topic in the field of agricultural ecology.The study of the effects of different amount of straw added on the organic carbon pool of black soil with two different organic carbon content can provide an important reference for improving the quality of the degraded black soil and optimizing the selection of the pattern of the straw restoration.In this experiment,two different kinds of straw were added to the black soil of high and low organic carbon content by the method of outdoor culture,and the change of the content of organic carbon content in black soil and the correlation between the components were studied.The results showed that all the straw with different added amount could increase TOC content of black soil with high and low organic carbon content,They increased by 1.39% to 40.80% and 2.27% to 17.2% respectively compared to the control,but the effect was more obvious for black soil with low organic carbon content.The improvement rates of straw for two kinds of black soil readily oxidizable carbon(ROC)were basically the same.The effect of different amount of straw on the microbial biomass carbon(MBC)and Water soluble organic carbon(WSOC)of the two black soils was similar,and both of them had significant effect on the black soil with low organic carbon(p<0.05).The addition of straw could significantly(p<0.05)improve the content of particulate organic carbon(POC)and the ratio of POC to total organic carbon in low organic carbon black soil,of which 2.5% straw treatment had the best effect.After adding straw to soil with low organic carbon content,soil microbial biomass carbon and water soluble organic carbon can reach the level of high organic carbon content in black soil without straw adding,which indicates that straw returning can significantly increase the content of soil active organic carbon.Significantly different treatment(p<0.05)increased the content of mineral-bound organic carbon(MOC),light fraction organic carbon(LFOC)and their ratio to TOC and the content of inert organic carbon(IOC)in the two black soils,and the improvement of low organic carbon black soil is better,but reduced the content of high fraction organic carbon(HFOC)and its ratio to TOC of two black soils.Correlation analysis showed that each component of soil labile carbon pool had a very significant correlation with TOC,and there was a significant correlation between the contents of ROC,MBC,WSOC,POC and LFOC with different straw addition ratios.The change of the content of ROC and POC are important influence factors for the change of organic carbon in black soil with high and low organic carbon content under different straw content.Mineral bound organic carbon and inert carbon have a very significant correlation with total organic carbon in soil stable carbon pool.but their correlation with HFOC was not obvious.The addition of different amount of straw has a certain effect on the black soil with two organic carbon contents,and application of high amount of straw can effectively enhance the organic carbon pool components of black soil with high and low organic carbon content,which is better for low organic carbon black soil,The best application rate is 2.5% by mass.Therefore,adding straw to degraded black soil is beneficial to the retention of soil carbon pool and increasing the content of each component of soil carbon pool. |
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