Soil Microbial Control Over Corn Stover Decomposition In The Croplands Of Black Soil

Straw is an important source of soil organic matter,which plays an important role in improving soil fertility and soil structure.Soil microorganisms are the drivers of organic matter interception and transformation.Returning straw to the field can provide rich carbon and nitrogen sources for soil microorganism activities and promote the growth and reproduction of microorganisms.Therefore,it is necessary to conduct in-depth research on straw carbon utilization strategies of soil microorganisms under different long-term straw returns.In this study,we used corn straw as a substrate to conduct indoor simulated constant temperature cultivation experiments.We systematically studied the dynamic changes of soil carbon and nitrogen turnover-related enzymes and the structure of soil microbial communities during the corn straw decomposition process under different long-term corn straw additions.The response of straw addition is to further understand and understand the soil microbial metabolism and response mechanism under the condition of straw addition,to lay a foundation for exploring the microbial utilization of straw carbon,and to provide a scientific basis for selecting reasonable and effective farming measures.The main results are as follows:1.In the early stage of straw decomposition(90d),bacteria dominate the soil microbial community structure.Soil bacteria,especially Gram-positive bacteria,may be the main decomposers of easily degradable components.With the continuous decomposition of the straw(90-120d),the soil microbial community structure changed from Gram-positive bacteria to Gram-negative bacteria,and the soil microbial flora gradually changed from bacterial to fungal.After 120 days,the structure of soil microbial community gradually stabilized,and fungi played an important role in the process of decomposition of difficult-to-decompose materials in the later stage of soil organic matter decomposition.The addition of straw increased the total PLFA content,bacteria,fungi,and actinomycetes in the soil,and reduced the ratio of Gram-positive bacteria / Gram-negative bacteria and the ratio of bacteria / fungus in the soil.After the corn stalks are returned to the field,the promotion of fungi is greater than that of bacteria.Fungi are the main participants in the decomposition of stalks.2.In the early stage of straw decomposition(90d),the decomposition of carbohydrates and other easily-degradable components was the main factor,but lignin could participate in the co-metabolic process.Then,with the increase of the culture time,the decomposition of cellulose,lignin and other difficult-to-decompose components gradually dominated,and the degradation of hard-to-degrade substances such as lignin in the soil took a long time.After 240 days of culture,the decomposition of phenols was the main factor.The addition of straw can promote the activities of soil ?-glucosidase,cellobiase,?-N-acetylglucosidase and leucine aminopeptidase,and as the amount of corn straw returned to the field increases,the soil hydrolase activity also showed an upward trend as a whole,but the increase in the amount of straw returned to the field did not significantly promote the activities of polyphenol oxidase and peroxidase.In the process of straw decomposition,soil carbon and nitrogen turnover related enzymes promote each other and have a synergistic effect in regulating the supply and demand balance of soil carbon and nitrogen.Changes in soil p H,total carbon,total nitrogen,and C/N will affect soil carbon and nitrogen turnover-related enzyme activities.3.Soil p H,total carbon,total nitrogen content,and C/N showed a downward trend with the increase of culture time.Returning straw to the field significantly increased soil p H,total carbon,total nitrogen content,and C/N,and the effect increased with the increase of the amount of returning straw to the field.