Optimization Of Composting Ratio On Multi-component Rural Wastes And The Application Effect Of Composting Products

The current situation of domestic rural waste,such as large production,scattered distribution and complex composition,not only increases the difficulty of collection,but also pose a challenge to efficient treatment.Aerobic composting is a conventional means of waste treatment,which not only effectively avoids ecological pollution,but also allows its back-end products to be used for resource utilization.At present,aerobic composting mostly focuses on single or two-component waste research related to rural production,such as livestock manure and straw,without co-treatment technology for rural toilet manure,kitchen waste and other household wastes.In addition,there is a lack of mechanistic research about the way and effect of resource utilization of rural waste composting products.Based on this,it is urgent to have an integrated solution for cooperative disposal of rural multi-component waste and efficient utilization of resources.In this study,four common rural solid wastes,namely,swine manure,human manure,rice straw and kitchen waste,were used as the main raw materials to optimize the four-component aerobic composting system based on the mix design model and to select the best composting material ratio.Secondly,the multi-component ratio optimization plan was used for scale up experiments to evaluate the quality of mixed compost products and to clarify the driving mechanism of biotic and abiotic indicators on the degree of maturity during the composting process.Finally,the controlled pot experiments were set up to elucidate the driving mechanism of compost product application on soil environmental quality and the regulatory role of inter-root microorganisms on the physiological response of pakchoi,which led to a suitable alternative for compost product application with chemical fertilizers.The main findings are as followed:（1）Based on the simplex-centroid experimental design,24 sets of experimental combinations were conducted,according to the changes of NI（NH₄⁺-N/NO₃^--N）,seed germination index（GI）and T（ratio of final C/N ratio to initial C/N ratio）maturity indicators,and it was found that the composting standard could be achieved at 25%～55%dry weight of swine manure,5%～25%of human manure and 35%～55%of straw,while 41.1%of swine manure,14.0%of human manure and 44.9%of straw were the best combination of composting materials.（2）The seed germination index（GI）,organic matter content and total nutrient content of the large-scale mixed compost product based on the optimal maturity ratio were 95.8%,37.24%and 5.62%respectively,indicating that the compost product was not only fully decomposed but also had a high nutrient level.In addition,compost maturity is mainly affected directly by compost physicochemical factors,and compost physicochemical factors can have specific indirect effects on GI by affecting fungal communities.（3）Soil environmental quality was evaluated on the basis of factor analysis for seven different application treatments,and it was found that the lowest soil environmental quality score was achieved in the single compost product treatment,while the highest soil environmental quality was achieved in the40%compost product replacement fertilizer treatment.Symbiotic network analysis revealed that compost products alone could shift the soil bacterial community towards nutrient-poor taxa,leading to a decrease in soil environmental quality,while compost product application treatment increased bacterial symbiotic network complexity and drove a shift in soil microbial community composition toward an increase in beneficial microflora,with Sphingomonas,Bacillus,Lysobacter and Massilia being the key bacterial species to improve soil environmental quality.（4）The combination of 40%compost product with 60%fertilizer at equal nitrogen levels had the highest agronomic,photosynthetic and quality index enhancement in pakchoi,while the 100%compost product treatment was the lowest among all fertilizer application combinations.The compost product combination affected the growth and quality indexes of pakchoi mainly by up-regulating the abundance of inter-root carbohydrate metabolism,lipid metabolism genes and abundance of symbiotic and saprophytic nutritional fungi,and decreasing the abundance of functional genes related to pathotrophic fungi.