Preparation Of Compound Microbial Fertilizer And Its Effect On Soil Improvement In Northwest Arid Mining Areas

The long-term over-exploitation of mining areas has brought about a series of environmental problems,while the dry climate,scarce rainfall and poor soils in the northwest have severely restricted the process of ecological restoration of abandoned mine sites.Compound microbial fertiliser combines the advantages of organic fertiliser and microorganisms and can improve the soil in mining areas very well.Therefore,in this study,six strains of Phosphate bacteria,Potassium bacteria and Diazotroph bacteria were selected from sheep manure for isolation and purification,and a composite bacterial agents was prepared,as well as the addition of biochar to prepare a biochar/microbial agent complex suitable for composting experiments.The aerobic composting of sheep manure and maize straw was carried out by adding biochar/microbial agent complex（BM）,biochar（B）and composite bacterial agents（M）to the piles to investigate the effects of different treatments on the physicochemical properties,nitrogen cycling,gas emissions and bacterial community succession during the composting process,and to conduct a comprehensive evaluation of the fertilisation efficiency by principal component analysis.Finally,a 30-day experiment was conducted to comprehensively evaluate the effect of the compound microbial fertilizer on soil improvement through principal component analysis,with a view to providing a theoretical basis for soil improvement in mining areas.The following conclusions were mainly obtained:（1）Two strains of inorganic phosphorus removal bacteria,two strains of organic phosphorus solubilizing bacteria,one strain of potassium bacteria and one strain of diazotroph bacteria were isolated and purified from fresh sheep manure taken from farms in Jiuyuan District,Baotou City,Inner Mongolia.It was also prepared as a biochar carried microbial agent to enable the microorganisms to successfully attach to the biochar.（2）The addition of biochar/microbial agent complex allows the compost to warm up quickly and extended thermophilic stage up to 9 days,while avoiding an anaerobic environment and to make the proportion of clumps<4 mm higher than 80%.After composting,the BM treatment group obtained lower E₄/E₆values and higher GI values,indicating that the addition of biochar/microbial agent complex accelerated compost stability and reduced phytotoxicity.In addition,the addition of biochar/microbial agent complex had a beneficial effect on the degradation of organic nitrogen and the rapid conversion of NH₄⁺-N to NO₃^--N.Compared to CK,the BM treatment group reduced CH₄,NH₃and N₂O emissions by 65.79%,42.05%and 68.64%respectively,contributing to a better reduction of greenhouse gas emissions.The addition of B,M and BM also contributed to the increased abundance of Proteobacteria,Actinobactenia and Firmicutes.The RDA results showed that EC was the main factor influencing bacterial community structure during the thermophilic and cooling stages.the TKN content mainly controlled the changes in bacterial community structure during maturity stages.In the overall analysis ranking,the BM treatment group scored 0.48 and had the best decomposition effect.（3）The treatment group with the addition of BM fertiliser is very good at increasing the EC,water content,organic matter and fast-acting nutrients of the soil,as well as increasing the types and numbers of beneficial micro-organisms such as bacteria and fungi in the soil.Soil p H,soil EC,soil water content,soil organic matter,soil fast-acting N,soil fast-acting P,soil fast-acting K,soil bacteria and soil fungi were analysed in relation to each other using five different treatments.The results showed good correlation between the soil indicators.The results of the comprehensive evaluation of the four treatment groups using the Soil Evaluation Index showed that all organic compost additions improved the soil well,with the BM fertiliser being the most effective,followed by the B fertiliser and the M fertiliser being the least effective.