Mechanisms Of Sandy Soil Fertility And Microbial Community Diversity Response To Conservation Tillage

Sandy soil was defined by loose structure,low organic matter and moisture content,and low microbial community diversity,resulting in low soil production.Conservation tillage have been proved to improve soil structure and fertility level and enhance crop yield effectively.Searching a appropriate tillage method was the key to promote the productivity of aeolian sandy soil.This experiment was conducted in Horqin Sandy Land in 2013-2017,involing in four conservation tillage managements(No-till,Straw mulching,Subsoling and Stubble)and conventional tillage.By studying the effect of tillage on soil physical,chemical and biological properties,we can definite the machanisms of sandy soil fertility and microbial community diversity response to conservation tillage.Finally,this study aimes to provide a theoretical basis for agricultural production in the region.1.Conservation tillage had a significant effect on soil physical and chemical properties.Compared with conventional tillage,soil bulk density at 0-40 cm under subsoiling was significantly reduced by 3.39%-8.78%.Conservation tillage could increase the soil moisture content,water storage and macroaggregate content by 7.75%-47.68%,9.31-50.91mm,5.52%-20.61%,respectively.Soil organic matter,total nitrogen,available nitrogen,available phosphorus and available potassium at the depth of 0-40 cm via conservation tillage were enhanced by 1.64%-14.51%,0.21%-23.70%,2.67%-16.85%,0.81%-25.95%and 1.55%-14.55%.From 2013 to 2014,subsoiling had the greatest impact on soil physical properties,while straw mulching performed best in 2015-2016.For soil chemical properties,straw mulching had the greatest improvement at the soil depth 0-20 cm,while subsoiling for 20-40 cm.2.Conservation tillage significantly increased soil enzyme activities at 0-40 cm depth in 2013-2016.Soil invertase,urease,alkaline phosphate and catalase activity increased by 0.91%-28.38%,4.00%-41.89%,0.87%-26.36%and 0.60%-33.90%,respectively.At 0-20 cm soil layer,straw mulching had strongest impact on soil invertase,urease and catalase,while subsoiling for alkaline phosphate activity;at 0-40 cm depth,the highest four enzyme activities under subsoiling.3.Conservation tillage increased the α-diversity indices for bacterial community than conventional tillage,with highest values under no-tillage.Conservation tillage increased the copiotrophic bacterial phyla Proteobacteria,Bacteroidetes,Gemmatimonadetes and four classes within Proteobacteria(α-,β-,γ-and δ-proteobacteria)through improving soil macroaggregate,moisture,soil organic matter and available nutrient content,while decreased the oligotrophic bacteria Chloroflexi,Acidobacteria,Firmicutes,Planctomycetes and Verrucomicrobia.Compared with conventional tillage,straw mulching increased Proteobacteria and Bacteroidetes by 29.14%and 36.76%,while no-tillage enhanced Gemmatimonadetes by 30.52%.Bacterial function predicted by FAPROTAX,the result indicated tillage had a significant effect on denifitier and nitrifier.Conservation tillage increased the relative abundance of Proteobacteria and Rhodoplanes for denitrificaiton,reduced the Crenarchaeota and Candidatus Nitrososphaera associated with ammonia oxidation and enhanced Nitrospirae and Nitrospira.4.The abundant fungal phyla across all soil samples were Ascomycota and Basidiomycota,dominated by Guehomyces,Alternaria,Mortierella,Cladosporium,Fusarium at genus level.Straw mulching enhanced Basidiomycota and Guehomyces via increasing of soil C:N ratio.Fungal functions predicted by FUNGuilds indicated that soil pathogenic fungi was decreased under conservation tillage by 36.56%-61.62%.Tillage management had more effect on the plant pathogenic community at one week after sowing,and conservational tillage reduced the relative abundance of plant pathogen,such as Alternaria,Fusarium and Cladosporium.5.Network analysis demonstrated that simple inter-relationships of bacterial and fungal taxa were observed in the conventional tillage soil,and no-till,straw mulching and subsoiling systems had a complex connection between bacterial and fungal taxa.Conservation tillage could enhance the number of key nodes and change the keystone taxa.Under conventional tillage,keystone taxa was dominated by Ascomycota,Bacteroidetes for no-tillage,and Proteobacteria and Ascomycota for straw mulching and subsoiling system.6.Conservational tillage significantly improved the componens of yield,maize yield,water use efficiency and economic benefit.Grain yield,straw yield and water use efficiency were enhanced by 3.25%-27.17%,3.22%-27.81%and 2.77%-24.99%.In 2013-2014,subsoiling had the highest grain yield and water use efficiency,while with increasing of year,the yield and water use efficiency gradually increased.Because of decrease in input,no-till always had highest input/output ratio.The degree of correlation between soil phisicochemial and enzymic activities and maize yiled revealed that total nitrogen,macroaggregate and available nitrogen has higher degree of grey correlation with maize yield.