Effects of maize stove on the harmlessness and maturity during the static facultative composting of pig manure

Static facultative composting is one of the most widely-used, cost-effective, lightweight, and simple technologies to utilize local resources in modern agriculture. More than 60% of livestock and poultry manure (especially pig manure) can be treated using static composting. Static facultative composting can also create an aerobic environment with low porosity and limited depth of air diffusion within the heap, resulting in the low metabolic activity of microorganisms. Degradation of organic matter can be inevitably delayed, due to the long fermentation cycles, low fermentation temperatures, incomplete harmlessness, and low product maturity. Alternatively, the straw can be added to adjust the physical structure, oxygen content, and C/N ratios of the heap, in order to effectively improve the rot degree of static facultative compost products for the short rot cycle. This study aims to explore the effects of straw control on the maturity and microbial community structure of static facultative composting, especially on pathogenic bacteria. The corn straw was taken to regulate the physical structure and C/N ratio of the pile. A 90-day static facultative composting experiment was conducted using traditional natural fermentation. A systematic investigation was made to clarify the maturation index, fecal coliforms, and microbial community structure in the static facultative composting. The composting device was set as a 100 L flanged iron hoop bucket. Two treatments were set up in total. The control group was set without pig manure to label as the P treatment. The mixed compost of pig manure and corn straw was labeled as the PC treatment. The wet base mass ratio of 4:1 was selected without ventilation and heap turning. The results showed that the straw regulation increased the porosity of the compost (increased by 19.41%), and then promoted the diffusion of oxygen to the interior of the compost for the better degradation of organic matter by aerobic microorganisms. Specifically, the contents of phytotoxic substances were reduced (such as NH4+-N and DTN) to improve the compost maturity. The seed germination indexes were 40.84% (P) and 114.60% (PC), respectively, in the two groups of compost products. As such, the compost maturation was accelerated during this time. The number of fecal coliforms reached the hygienic safety standard after 30 to 40 days of natural fermentation. Furthermore, the activity of fecal coliforms depended on the temperature of the pile, NH4+-N, and organic acid content. The corn straw was added to improve the diversity of bacteria and synergistic effect. Firmicutes, Actinobacteria, Proteobacteria, and other phylum related to lignocellulosic degradation were the dominant microbial phylum in the reactor, where the aerobic, facultative, and anaerobic microbial stratification was formed from the aerobic to anaerobic bacteria from the top to the bottom. Therefore, the corn straw regulation can be expected to increase the aerobic area of the pile in the process of static composting. The harmless and mature degree can be promoted in the static composting of pig manure. The finding can provide the theoretical basis and technical standardization support for the static composting of livestock and poultry manure.