Influence Of Sewage Sludge Biochar-mediated On Sandy Soil Improvement And Its Evaluation On The Yu-Dong Plain

The Yu-Dong plain is an important grain production base in chaina.Affected by the change of lower reaches of the Yellow River,flood and Yellow River diversion irrigation project,the area is widely distributed with sandy soil.Sandy soil is poor in structure,low in nutrients,and prone to wind erosion.This seriously threatened the strategic role of the Yu-Dong plain in the national grain production.Therefore,how to improve the sandy soil and the quality of cultivated land is particularly urgent for the sustainable development of regional agriculture.Sewage sludge is the product of sewage treatment,containing a large number of nutrients and organic substances.Carbonization treatment of is an effective disposal to realize sewage sludge reduction,innocuity,stabilization and resource recovery,and to provide guarantee for agricultural utilization of sewage sludge.In order to further understand the improvement effect of sewage sludge biochar on the physicochemical properties and biochemical properties of sandy soil,field experiments were carried out from 2016 to 2018.0,20,40,60 t/hm²(CK,B20,B40,B60)were added to the soil(0?30 cm),respectively,to explore the soil fertility and action mechanism under the action of sewage sludge biochar.The effects of sewage sludge biochar on soil organic carbon pool,microorganism,enzyme and mineralization were studied.The results provide theoretical reference and technical guidance for the improvement of sandy soil and sustainable development of farmland production in China.The main research results are as follows:(1)The application of sewage sludge biochar improved soil structure,soil water retention,fertilizer retention capacity,and soil nutrient level.Specifically,it significantly reduced soil BD,p H and TK,improved soil porosity,aggregate,water holding capacity,SOC,TP,AP,CEC,K⁺,Mg²⁺,and had little impact on AN,Ca²⁺and TN.The effect of sewage sludge biochar on AK,K⁺and Mg²⁺decreased year by year.The improvement effect of soil physical and chemical properties was enhanced with the increase of application amount,and B60 treatment had the best effect.(2)The application of sewage sludge biochar enhanced the stability of SOC and accelerated the SOC cycle.From the third year of application,the sewage sludge biochar treatment significantly reduced the alkyl oxygen carbon ratio and increased the aromatic carbon and carboxyl carbon ratio,while the alkyl carbon did not change much.For the soil group carbon content ratio,the sewage sludge biochar treatment significantly increased the alkyl/alkoxane,hydrophobic/hydrophilic,aromatic degree,reduced the aliphatic/aromatic.B40,B60 effect is better than B20.NMDS atlas showed that the molecular structure of SOC in soil was significantly different between different treatments,and the increase of application amount and the extension of application duration gradually changed the molecular structure of SOC.Sewage sludge biochar significantly affects soil labile organic carbon(DOC,POC,LFOC,EOC,MBC),in addition to reducing DOC.On the whole,labile organic carbon content of sewage sludge biochar was increased,and the content of B40 treatment was the highest.(3)The application of sewage sludge biochar improved the soil enzyme activity and microbial biomass,but the effect on different soil enzymes and microbial communities was different.The activity of soil catalase and invertase was increased by sewage sludge biochar in three years,and alkaline phosphatase activity was increased in the third year,the effect on urease activity was not significant.The soil enzyme index increased by 176.35%?253.58%,148.37?369.57%and 65.77?337.09%,respectively.The application of sewage sludge biochar changed the structure of soil microbial community,and significantly increased the contents of microbial biomass,gram-positive bacteria,gram-negative bacteria,actinomycetes and fungi.Redundancy analysis(RDA)indicates that soil microbial community is closely related to soil physical and chemical properties,such as p H,organic carbon,total nitrogen,cation exchange capacity,available potassium,etc.,indicating that the long-term effect of sludge biomass carbon on soil microbial community structure may be indirectly driven by changes in soil characteristics.Soil enzyme activity index(SEI)and microbial diversity index(H)of B60 treatment were significantly lower than those of B40 treatment,indicating that B60 treatment inhibited soil enzyme activity and microbial growth,and B40application amount was more beneficial to the improvement of soil microbial activity and enzyme activity.(4)Laboratory culture experiment was used to study the effect of sewage sludge biochar application on soil organic carbon and nitrogen mineralization.The results showed that the application of sewage sludge biochar could reduce soil respiration intensity,organic carbon mineralization rate and accumulated mineralization amount,but had no significant effect on organic nitrogen mineralization rate and nitrification rate.The relationship between soil organic carbon mineralization rate and culture time was logarithmic.BRT analysis results showed that TN and DOC were the largest factors affecting SOC accumulation,mineralization potential and Cp/SOC.The kinetic equation simulated the characteristics of organic carbon mineralization.The results showed that the SOC mineralization rate of sandy soil in the study area was high,and the soil carbon fixation capacity of B20 treatment was better than that of B40 and B60 treatment.(5)The application of sewage sludge biochar improves the soil environment and soil fertility level,thus promoting crop growth and achieving the effect of improvement and yield increase.The application of sewage sludge biochar increased the root activity of peanut,which was beneficial to the growth of crop roots and plants,and improved the productivity of peanut.The effect of sewage sludge biochar on peanut yield increased gradually with the extension of application years.In the third year,B20,B40 and B60 treatment increased by 10.91%,22.59%and 19.22%,respectively.B40 treatment had the largest effect on peanut yield.(6)The quality level of soil improved by sludge biomass carbon was comprehensively evaluated.Principal component analysis was used to evaluate 24 main indexes of soil quality,and the results showed that soil quality could be characterized by 4 principal components,with an interpretable cumulative variance of 88.166%.Overall,the comprehensive index of soil quality improved by different treatments showed that the sewage sludge biochar treatment was higher than the CK treatment,indicating that the sewage sludge biochar had a good improvement effect.Among them,the comprehensive index of soil quality under B40 treatment was the highest,reaching 0.62,indicating that 40 t/hm² had the best improvement effect.To sum up,this study found that the application of sewage sludge biochar can improve the problems of poor soil structure,water leakage and fertilizer leakage,and poor organic matter in sandy soil,and effectively improve the productivity of cultivated land.The application of sewage sludge biochar can be used as a sustainable way to improve soil quality.The comprehensive analysis of the impact of sewage sludge biochar application on a variety of soil indexes and yield shows that 40 t/hm² is the most suitable amount in sandy soil.This study provides strong evidence for correctly evaluating the improvement effect of sewage sludge biochar on sandy soil.