Effect On Soil Quality Of Sandy Fluvo-aquic Soil By Application Of Fermentation Product Of Sewage Sludge

The fermentation products of sewage sludge(CS)were utilized in the accordance of the national standard in the experiment with sandy fluvo-aquic soil under wheat-maize rotation system during 2013 to 2015.The experiment focused on the effects of soil fertility and health,enzyme activity and microbial community composition by the use of fermentation products of sewage sludge for providing theoretical and technical basis for the resource utilization of sewage sludge.The four treatments,with varying doses of CS and a control,were as follows:(1)CK,inorganic fertilizers alone;(2)CS1,inorganic fertilizers and 15 t ha-1 of CS;(3)CS2,inorganic fertilizers and 30 t ha-1 of CS;(4)CS3,inorganic fertilizers and 45 t ha-1 of CS.The results were shown as follows:1.Soil p H of the same treatment decreased over time and soil organic matter(SOM),total nitrogen(TN),available phosphorus(AP),and available kalium(AK)increased over time.In 2015 maize season,compared to CK,soil p H in CS-treated soils significantly decreased by 0.34-0.83(P <0.05)and the dose of CS was negatively correlated to the p H;SOM,TN,AP and AK in CS-treated soils significantly increased by 52.08 %-166.85 %,77.25 %-177.84 %,215.67 %-486.26 % and 167.20 %-378.96 %(P <0.05)respectively and they were positively correlated to the does of CS.Microbial biomass carbon and nitrogen(MBC and MBN)and MBC/MBN were significantly increased in CS-treated soils(P <0.05).Different season can also cause a significant influence on MBC,MBN and MBC/MBN(P <0.05).The results revealed that applying fermentation products of sewage sludge can effectively adjust soil acidity and alkalinity,improve soil fertility and make soil microbial community dominant by fungi.2.Compared with CK,soil amended sludge significantly enhanced MBC,labile organic carbon(LOC),and dissolved organic carbon(DOC)by 84.00 %-188.07 %,26.26 %-58.03 %,and 109.58 %-185.39 %(P <0.05)respectively,and CS3 had the most significant impact on soil carbon pool.The soil microbial entropy(MBC/TOC),and utilization of labile organic carbon(LOC/TOC)raised by 8.02 %-2.77 % and 13.75 %-46.48 % respectively,and the utilization of dissolved organic carbon(DOC/TOC)significantly decreased by 17.06 %-40.94 %(P <0.05).MBC/TOC,LOC/TOC,and DOC/TOC were declined in treatments of soil amended sludge due to increasing the application of fermentation products of sewage sludge,which indicated that soil amended 45 t·hm-2 of the fermentation products of sewage sludge improved the content of stable carbon resulting in the decease of the ratio.L and LI decreased with the increasing amount of fermentation products of sewage sludge indicating that soil amended 45 t·hm-2 of the fermentation products of sewage sludge improved the content of stable carbon and was conducive to the accumulation of organic carbon.Soil amended sludge significantly increased carbon pool management index(CMPI)by 17.06 %-40.94 %(P <0.05),and CS3 had the most significant effect on CMPI.Compared with TOC,CMPI could be more sensitive,direct to reflect the dynamic changes of soil nutrients and carbon pools through the correlation analysis and redundancy analysis.3.Compared to CK,the content of heavy metal of soil and plant grain accumulated after the application of CS,but its value is far below national environmental quality standards(GB15618-1995)and limited value made by agricultural product quality safety regulations of the state.The results indicated that the does of CS used in this study do not cause the heavy metals pollution to the soil and grain.4.Compared to CK,absolute enzyme activities except phosphatase significantly increased in CS-treated soils,but soil specific enzyme activities significantly decreased in CS-treated soils(P <0.05).This implied that decreasing enzyme production and release by microorganisms.Soil microbial functional diversity decreased as the dose of CS increase while soil microbial community composition diversity increased in CS-treated soils,suggesting the domination of microorganisms that are not metabolically active and of more organisms using resources more efficiently(fungi).Both PCA and RDA revealed that fundamental changes in soil enzyme activity depended on soil p H,and the Pearson correlation coefficient showed that soil specific enzyme activity is more closely affected by soil properties than absolute activity.In general,specific enzyme activity proved a clearer and more useful indicator in detecting and assessing the alterations in in the metabolic status of the microbial community in soil following CS application to sandy fluvo-aquic soils.5.Compared to CK,soil bacteria richness(ACE and Chao1)was significantly improved in CS-treated soils,while there was no significant difference in soil bacteria evenness(Shannon and Simpson indices).Phyla Proteobacteria,Acidobacteria,Chloroflexi,Gemmatimonadetes,and Saccharibacteria increased in CS-treated soils,whereas phyla Actinobacteria and Firmicutes decreased.Results from principal coordinates analysis indicated that the bacterial communities were highly varied in soils where more CS were used(CS2 and CS3).Soil p H and total nitrogen content appeared to be the most important impact factors for bacterial communities according to the results of redundancy analysis.Our findings suggested that consecutive application of CS can improve the bacterial biodiversity,and change the bacterial community composition.In summary,CS application can ensure the safety of soil and plant grain.Based on this,applying CS,especially CS3,can effectively improve soil fertility of poor sandy fluvo-aquic soils,increase intrinsic activity of soil organic matter and improve soil microbial properties.This approach represents a practical way and have profound guiding significance for overcoming predominant stress factors f sandy fluvo-aquic soils,improving soil productivity and establishing national food security mechanism.