| Aiming at the problems of low and uneven rainfall,low organic carbon content,p oor soil structure,and low water and fertilizer retention capacity in the dryland hilly a rea of the Loess Plateau,which lead to low and unstable crop yield.this paper conduct ed three consecutive years of field positioning experiments.To study the application o f straw and bentonite on soil physical and chemical properties,soil organic carbon and its fractions,organic carbon related enzyme activity,microbial community structure,t he influence of oat production,reveal the mechanism of combined application of stra w and bentonite on carbon sequestration,moisture conservation and yield Increase for oat production in dry Farming Land,the aim is to provide theoretical basis and techn ical support for the improvement of soil organic carbon and moisture storage capacity in dry farming land.The main findings are as follows:1.The combined application of straw and bentonite significantly（P<0.05）increased the grain and biomass yield of oat.Compared with CK,the grain yield and biomass yield were increased by 20.93%and 31.95%,the economic benefit of oat production has been improved for three consecutive years,and the average annual increase in income benefit is 873.36 yuan per hectare.2.The combined application of straw and bentonite significantly improved soil structure,increase soil moisture and available nutrient content.Straw combined with bentonite significantly（P<0.05）decreased soil bulk density,and increased soil porosity in 0-40cm soil layer,promoted the formation of soil>0.25mm aggregates,and improved the stability of aggregates.In the five key growth periods（Seedling stage,Jointing stage,Heading stage,Filling stage,Maturing stage）,the soil water storage capacity of 0-100cm soil increased by 10.00%,13.44%,9.31%,8.11%,and9.99%,and the field water capacity and water use efficiency of 0-40cm soil increased by 16.10%and 25.25%on average in 3 years.The ratio of rainfall to total water consumption was increased,and the ratio of soil water consumption to total water consumption was decreased in the early growth stage of oats,while the ratio of soil water consumption to total water consumption was increased in the middle growth stage of oats.which had no significant effect on the later growing period.The contents of AN,AP and AK in 0-40cm soil layer were significantly increased（P<0.05）.3.The combined application of straw and bentonite has affected the bulk soil and aggregate of soil enzyme activity of 0-40cm soil layer.Compared with CK,straw combined with bentonite treatment increased the activities of invertase,β-glucosidase,α-glucosidase,cellulase and catalase in the bulk soil and>0.25mm aggregates.The contribution rate of>0.25mm aggregates to soil enzyme activity was increased.4.The combined application of straw and bentonite affects the total organic carbon and its fractions in the bulk soil and aggregates of 0-40cm soil layer.Compared with CK,the straw combined with bentonite treatment improved the soil organic carbon and dissolved organic carbon,liable organic carbon,microbial amount of organic carbon,organic carbon mineralization,particulate organic carbon,light fraction organic carbon of bulk soil and aggregates,improved the>0.25 mm aggregate of organic carbon and its fractions on the contribution of soil organic carbon.5.The combined application of straw and bentonite promoted soil organic carbon sequestration of 0-20cm soil layer.Compared with CK,straw combined with bentonite treatment significantly increased carbon input by 169.19%(4.98 Mg?hm-2)and organic carbon storage in the bulk soil and>0.25mm aggregates.The soil organic carbon sequestration and carbon sequestration rate were 1.37 Mg·hm-2and0.46 Mg·hm-2·a-1,respectively.Increased by 1.45 times and 1.49 times,respectively.There was a significant positive correlation between SOC sequestration in bulk soil and SOC storage in aggregates>0.25mm and carbon input.SOC content was mainly increased by increasing SOC sequestration in>0.25mm aggregates.6.The dominant bacterial phylum in soil were Actinobacteria,Proteobacteria,Chloroflexi and Acidobacteria.The dominant fungal phylum in soil were Ascomycota,Mortierellomycota and Basidiomycota.Compared with the control,the combined application of straw and bentonite changed the microbial community structure,increased the abundance of bacterial Actinobacteria,Firmicutes and Chloroflexi,and the abundance of fungal Ascomycota,Basidiomycota and Glomeromycota,reduced the abundance of pathogenic bacteria such as Leptosphaeria and Alternaria,and increased the abundance of anti-pathogenic bacteria such as Streptomyces,Streptomyces and Chaetomium,which helped to create a healthy soil environment.The combined application of Straw and bentonite can promote the formation and stability of>0.25mm aggregates,effectively improve soil structure,enhance soil water and nutrient storage capacity,and promote soil organic carbon sequestration and crop yield. |
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