Study On Microbial Community Structure In Novel Static Aerobic Composting Of Cow Manure

Composting technology is the most effective method to dispose agricultural waste.However,the effect of the surface and inner fermentation of static composting is not sufficient due to the distribution of temperature and oxygen is not uniform.A novel static composting system was designed to deal with the disadvantages of traditional composting in this study.Microorganism played an important during composting process which can determine the composting process and the quality of the compost.Therefore,studying microbial community structure in composting had scientific value for enriching the composting theory and improving the composting technology.A novel static composting system was using in this study,in which dairy manure and rice straw were mixed to prepare the compost.The degree of the maturity of composting was verified by physicochemical and biological parameters,and the composition and dynamic changes of bacterial and fungal community structure during composting were tested by new generation of high-throughput sequencing technology.We also explored the relationship between microbial community composition and physicochemical and biological parameters.The main results of the study were as follows:（1）Composting lasted for 17 days.On the 3rd day,the center and outer temperature of the composting were higher than 55℃,and the compost entered the thermophilic phase for 9 days（3 d¹2 d）.During the whole composting process,the pH value kept decreasing and maintained in the alkaline condition,the moisture content also showed a downward trend,and falling to 51.0%when the composting ended.NH₄⁺-N first increased and then decreased,and reached the maximum(932.2 mg·kg^-1)in the mesophilic phase,then gradually decreased;NO₃^--N increased slowly and reached the maximum(95.5 mg·kg^-1)in the maturation phase.With the progress of composting,the seed germination index also gradually increased and reached 97.7%when the composting ended.According to the physicochemical and biological parameters,cow manure compost reached maturity after 17 days.（2）Using high-throughput sequencing technology to study the composition and dynamic changes of bacterial and fungal community structures during the composting process.The results showed that the number of OTU and the Shannon diversity index of bacterial and fungal communities had the same trend during composting process,and both increased first and then decreased,but the richness and diversity of bacterial community were significantly higher than those of fungal community.With the process of composting,the community structure of bacteria and fungi changed obviously.（3）At the level of phylum classification,the bacteria phyla that dominate in the initial stage of composting were Proteobacteria and Bacteroidetes,while in the thermophilic phase,Firmicutes was the dominant phylum.When the compost entered the high temperature phase,Actinobacteria and Chloroflexi were the dominant phyla.And for fungi,Basidiomycota was the dominant phylum in the initial phase of composting,while the dominant fungal phylum was Ascomycota after the composting entered the thermophilic phase.（4）At the level of genus classification,the most abundant bacterial genera in the initial phase were Petrimonas,Hydrogenophaga,Acinetobacter,Flavobacterium and Comamonas,while Mythylocaldum,Luedemannella,Luedemannella,Thermopolyspora and Thermomonospora were the dominant bacteria when composting entered the maturity stage.And for fungi,the most abundant fungal genera in the initial phase were Wallemia and Trichosporon,while Unclassified Ascomycota and Coprinus were the dominant fungi in the maturity stage.（5）The relationship between microbial community composition and physicochemical and biological parameters results showed that the bacterial genera Thermopolyspora and Thermomonospora was positively correlated with total nitrogen,nitrate nitrogen and seed germination index（p<0.05）,but negatively correlated with the moisture content,total carbon,C/N and ammonium nitrogen（p<0.05）.Similarly,the fungal genus Coprinus was positively correlated with total nitrogen,nitrate nitrogen and seed germination index（p<0.05）,but negatively correlated with the moisture content,total carbon,C/N and ammonium nitrogen（p<0.05）.