| Municipal sludge and livestock manure are important solid wastes in the urban environment,which must be treated and disposed reasonably to reduce the environmental pollution.Aerobic composting is an effective biological method to degrade and stabilize organic matter,inactivate pathogens and recover nutrients.This study explored the changes of microbial community composition,trophic modes,metabolic functions as well as their correlation with environmental factors during sludge and sawdust composting,revealed the differences and interaction between the microbial structure in sludge and sawdust,and provided a basic understanding the internal mechanism of microbial succession in the composting system.In addition,exploring the effects of organic fertilizer on soil carbon,nitrogen,phosphorus,potassium and soil microbial diversity and carbon source metabolic capacity are of great significance to the quality inspection of organic fertilizer,the improvement of nutrient release efficiency and the optimization of fertilization schemes.The results showed that the fugal composition of sludge was mainly affected by pH(42.4%),moisture content(35.9%)and ORP(21.7%).The composition of bacteria was mainly affected by VS(42.6%),C/N(34.9%)and temperature(22.5%).However,the fungal composition in sawdust was mainly affected by VS(41.1%),temperature(34.7%)and moisture content(24.2%).The changes of bacterial composition in sawdust could be explained by ORP(42.9%),temperature(31.9%)and moisture content(25.2%).The difference and interaction of environmental factors between sludge and sawdust was the driving forces of microbial transfer.The soil conductivity of fresh livestock manure and sludge as well as their compost products showed an upward trend after treatment.The composting products of livestock manure and sludge have a stable effect on soil pH and ORP.The total phosphorus content in soil increased by 36% and 24%,and the available phosphorus content increased by 70% and 60% after 150 days of application of pig manure compost and chicken manure compost,respectively.The total potassium content of soil treated with pig manure compost and chicken manure compost increased by 32.0% and 23.7%,and the available potassium increased by 46.2% and 43.5% in the early stage of fertilization,respectively.The application of compost products in the initial stage of soil significantly increased the contents of total carbon,organic matter and soluble organic carbon.Pig manure compost had the highest total carbon content in the soil after treatment,which was 1.15 times higher than that of non-fertilization treatment.Soil organic matter(SOM)levels increased by 39.1%,21.4%,34.5% and 29.7% after 150 days of treatment of pig,cattle,chicken and sludge compost products,respectively.Soluable organic carbon(SOC)increased by 131.2%,55.2%,104.8% and 81.1%,respectively.The application of compost products in soil can improve the soil total nitrogen,soluble total nitrogen,ammonium nitrogen and nitrate nitrogen to a certain extent,and show a trend of increasing first and then decreasing during the period of fertilization.After 150 days of treatment of pig,cattle,chicken manure and sludge compost products,total nitrogen content increased by 24.6%,21.4%,17.1%,16.6%,total dissolved nitrogen increased by 51.4%,58.8%,69.3% and 57.9%,respectively.On the fiftieth day,ammonium nitrogen increased by 350%,150%,370%,210%,290%,210%,250%,250% and 160% respectively,and nitrate nitrogen increased by 126.9%,107.7%,157.7%,100.0%,115.4%,88.5%,92.3%,80.8% and 96.2% respectively.ORP value(40.8%),organic matter content(38.2%)and total nitrogen(21.0%)were the main factors affecting the change of soil bacterial composition.Metabolism-related gene abundance in soil after compost treatment were significantly increased.This was consistent with the results of microbial carbon metabolism.Composting products of livestock and poultry manure and sludge significantly increased soil microbial metabolism,which was 2,1.5,2.1 and 2.3 times as much as that of non-fertilized treatment. |
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