| Soil organic matter formation pathway and stabilization mechanism have always been an important scientific issue in the field of soil science,especially in recent years,more and more studies have focused on the role of microorganisms in the formation of soil organic matter.In this study,the chemical components of organic matter were studied by pyrolysis gas chromatography-mass spectrometry under long-term no-tillage condition,and the response of each component of soil organic matter to environmental changes was explored under the condition of adding exogenous organic matter.This experiment is based on the research and development base of conservation tillage of Chinese Academy of Sciences,located in Gaojia Village,Dafangshen Township,Lishu County,Jilin Province.Since 2007,a 10-year experiment on different straw mulching was conducted under no-tillage conditions.Four no-tillage treatments with straw mulching were set up,namely,no-straw mulching(NT-0),33%straw mulching(NT-33),67%straw mulching(NT-67),and 100%straw mulching.Cover(NT-100).Through the analysis and determination of organic carbon and total nitrogen in different soil layers(0-5cm,5-10cm,10-20cm)in 10 years,it was found that no-tillage straw mulching had the most positive effect on farmland soil.Therefore,we further studied the organic matter composition of surface soil(0-5cm),and discussed the effect of straw mulching on soil organic matter under no-tillage condition.Influence.The main test results are as follows:1.Our results show that long-term no-tillage treatment can improve the content of organic carbon(SOC)and total nitrogen(TN)in the surface soil of farmland,and the promotion effect of no-tillage treatment combined with straw mulching is stronger.In addition,straw mulching improved the surface soil quality,which showed the increase of soil water content and the decrease of bulk density.2.In the first year of no-tillage and mulching,there was no significant difference among treatments.In the fifth year,plant source components(Phenol)contributed mainly to the difference of SOM molecular structure among different treatments,while in the tenth year,microbial source(N-compound)components contributed mainly.3.During the 10-year period,the components with increasing relative content were lignin,phenolic and lipid components,which indicated that plant-derived components had great influence on the molecular structure of SOM in the surface layer under long-term conditions.Under the effect of microbial modification in vitro,a large number of plant-derived components were accumulated in the soil which were difficult to decompose.At the same time,microbial assimilation of exogenous organic matter components can preserve surplus fertilizer nitrogen in the form of "transitional reservoir" in the soil,increasing soil microbial source organic matter.The application of no-tillage straw mulching and returning technology in farmland ecosystem can promote the increase of organic matter content through two ways:in vivo turnover of soil microorganisms and in vitro modification,which is of positive significance for improving soil fertility and sustainable agricultural development.In conclusion,this study provides a new idea for the source of soil organic matter molecular components and the assessment of the relative contribution of microorganisms and plants to organic matter,and further verifies the importance of soil microorganisms to the formation and stability of soil organic matter in different ecosystem types through experiments.This study provides a strong theoretical basis for taking reasonable measures in soil management to promote the accumulation of organic matter and improve soil fertility. |
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