Effects Of Straw Addition On Mineralization And Components Of Organic Matter In Soils With Different Properties And Tillage Types

Farmland ecosystem is the main component of terrestrial ecosystem,and it is also the ecosystem most affected by human activities.Straw returning is one of the most commonly used ways of resource utilization.Under the background of increasing climate warming,soil organic matter（SOM）mineralization characteristics and influencing factors of farmland soil straw returning have gradually become a research hotspot.However,there is no unified understanding of the response mechanism of soil with different properties to straw addition.In order to explore the response mechanism of SOM and dissolved organic matter（DOM）components to straw in soils with different organic matter content content,iron content and soil type.In this study,the red soil of farmland Heshengqiao in Xianning City,Hubei Province is taken as the research object,and short-term and long-term incubation experiments is proformered.The main results are as follows:（1）The addition of straw can increase the mineralization of soil organic matter and increase the utilization rate of soil nitrogen.The cumulative emissions of CO₂ and N₂O from straw addition treatment are 1.96⁴.89 and 1.02².25 times higher than those of control group.The maximum emission rates of CO₂ and N₂O increased significantly with the addition of straw.Dissolved organic carbon（DOC）content in soil increase by32.03%⁹6.63%,and water extractable nitrogen（WEN）content decrease by11.12%⁶4.77%,the interaction between soil iron oxide and organic matter content significantly affects nitrogen mineralization.（2）The process of straw decomposition can promote the accumulation of soil organic matter.The immobilization of SOM by low organic matter soil is higher than that of high organic matter soil,and the mineralization degree of low organic matter soil is lower than that of high organic matter soil.The addition of straw increased SOM content by 3.92%⁷7.59%in low organic matter soil and 2.49%¹3.73%in high organic matter soil.After long-term cultivation（180d）,the cumulative emissions of CO₂ and N₂O in high organic matter soil are 1.19 and 1.96 times higher than those in low organic matter soil,respectively.（3）The contents of DOM components in soil decreased gradually with incubation time.The DOC content in soil decrease by 29.97%⁶3.64%after culture（180d）compared with the initial stage（1d）.DOM in each treatment group containe more fatty compounds,organic acids,carbohydrates and other substances in the early stage of culture,and these substances gradually decrease in the later stage of culture.（4）Straw addition accelerate the turnover of DOM components in soil.With the addition of straw,DOM aromaticity and humification of soil increase by 3.48%⁴.84%and 10.40%¹2.30%respectively.And the fluorescence intensity of protein-like tyrosine,protein-like tryptophan,fulvic acid,soluble microbial by-products and humic acid-like components in soil DOM increase by 24.86%⁴3.91%.And the proportion of fluorescent components of tyrosine-like compounds is reduced.（5）Soils with different organic matter content have different DOM properties and components.Soil organic matter content can affect DOM bioavailability,fluorescence intensity and humification index.The fluorescence intensity and humification index of DOM in low organic matter soils are 7.83%and 49.60%higher than those in high organic matter soils,respectively.Tyrosine-like and soluble microbial by-products in DOM of high organic matter soil are 15.70%and 7.61%higher than those of low organic matter soil,while fulvic acid-like components are 16.27%lower than those of low organic matter soil.（6）The SOM mineralization of paddy soil is higher than that of upland soil,and the nitrification of paddy soil is enhanced by the addition of straw.The CO₂ and N₂O emissions of paddy soil are 1.21 and 1.39 times higher than those of upland soil,respectively.The NO₃^--N content of upland soil decrease by 46.79%and that of paddy soil increase by 6.87%with the addition of straw.