Effect Of Continuous Application Of Soil Amendments On Soil Quality Of Sandy Fluvo-aquic Soil

Two typical organic and inorganic desertification soil amendments are the research objects.Three-year?2015?2018?field experiment was carried out in sandy tidal soil in Langfang City,Hebei Province to study how soil amendments affected soil quality and soil environmental behavior.there were four treatments:(CK:no soil amendment;T1:CK+organic amendment,15t·hm^-2;T2:CK+inorganic amendment,2.25t·hm^-2;T3:CK+organic amendment 15t·hm^-2+inorganic amendment2.25t·hm^-2).Related indicators of soil physical and chemical properties,enzyme activity and microbial community structure were measured.The effect of soil amendments on soil quality and its mechanism of action were discussed,with a view to providing a theoretical basis for the development and application of soil amendments and Sandy Fluvo-aquic Soil improvement.The results are as follows:1.Application of soil organic amendment resulted in a significant increase of soil nutrient contents and soil comprehensive fertility.Soil organic matter,available phosphorus,and available potassium all increased significantly under T3 comparing to CK?P<0.05?,while soil pH decreased significantly.T1resulted in a significant increase of soil available potassium,decrease of soil pH comparing to CK?P<0.05?.therefore,T3 and T1 were better than T1 for improving soil properties.Soil comprehensive fertility index?IFI?increased under modifier application,and was in order of T3>T1>T2>CK.these results proposed that continuous application of organic amendment can improve soil fertility in sandy fluvo-aquic soil,and adjust soil pH condition.2.Application of organic amendment resulted in an increase of of soil labile carbon content and components,soil carbon pool management index,carbon pool capacity,and soil quality.The contents labile carbon pools increased under organic amendments,and were in the order of oxidized organic carbon?LOC?>dissolved organic carbon?DOC?>microbial biomass carbon?MBC?.The ratio of labile carbon pool to soil total organic carbon?TOC?decreased significantly comparing to CK.For example,LOC/TOC under T1 and T3 was reduced by 12.57%and 12.02%?P<0.05?,respectively.The ratio of MBC to TOC under T1 and T3 reduced by 12.84%and 12.30%?P<0.05?,respectively.While there were no differences of the ratios under T2 comparing to CK.;The CPMI of each treatment increased by6.11%-10.64%compared with CK.3.Application of soil amendments resulted in an increase of the proportion water-stable aggregate and an improvement of aggregate structure.Both T1 and T3 significantly increased the content of sandy WR0.25?P<0.05?,and T3 prior to T1.Application of organic amendment significantly promoted the formation of large-sized aggregates from small-sized aggregates,and it was much better than inorganic amendment.In addition,T1 and T3 increased geometric mean diameter?GMD?.Soil amendments resulted in an increase of the average mass diameter?MWD?comparing to CK,and the MWD was largest under T3 This means that both organic and inorganic amendments can improve soil structure in sandy fluvo-aquic soil.4.Application of soil amendments increased soil enzyme activity.comparing to CK,The activity of?-glucosidase and Cellobiohydrolase increased by 42.97%and 63.96%under T1 and T3,respectively;The activity of Acetylglucosaminidase increased by 114.57%,106.36%,and 227.8%under T1,T2,and T3,respectively;The activity of Leucine aminopeptidase increased by 23.58%and 15.83%under T1 and T2,respectively.The activity of Soil phosphatase increased by 37.27%and 37.83%under T1 and T3,respectively.The activity of polyphenol oxidase under T1 and T3 increased significantly by27.59%and 48.61%?P<0.05?,respectively.Redundancy analysis and Pearson correlation analysis showed that p H and labile organic carbon had the most profound effects on enzyme activity.The correlation coefficients of pH and all enzymes are negative,of which peroxidase?PER?reaches a significant negative correlation?P<0.05?,and polyphenol oxidase?PPO?Very significant negative correlation?P<0.01?,indicating that pH is the most important factor affecting soil enzyme activity.5.Application of soil amendments had great effects on microbial community structure in Sandy fluvo-aquic soil.Both T1 and T3 increased the abundance of Acidobacteria and Firmicutes at bacterial phylum level,and decreased the abundance of Proteobacteria.Both T1 and T3 increased the abundance of Mortierellomycota at fungi phylum level,and the abundance of Sordariomycetes,Dothideomycetes,and Mortierellomycetes at fungi class level.Microbial taxonomy diversity and abundance were closely related to soil environment and nutrient condition according to redundancy analysis and Heatmap correlation analysis.Soil organic carbon and labile pools significantly affected the community of Olpidiomycetes and Agaricomycetes at fungi class level.There was a negative relationship between the abundance of Saccharomycetes,Rozellomycotina?cls?Incertae?sedis,Blastocladiciomycetes,Agaricomycetes and activities of PPO and PER.In summary,organic amendment are superior to inorganic amendment in increasing soil nutrient content,soil carbon storage capacity and soil extracellular enzyme activity,improving soil microbial community structure,and cultivating soil fertility.Organic-inorganic amendment are applied in combination There is no significant difference from single application of organic modifiers,indicating that organic modifiers are the main driving factors for improving soil fertility;both modifiers can increase the number of sandy soil aggregates,improve aggregate structure,reduce soil bulk density,and improve soil quality.The combination effect of the two modifiers is the best,and there is no significant difference between the two.The research results are of guiding significance for farmers to choose soil amendments according to the purpose of improvement.