Dynamics of Bacterial Diversity and Functions with Physicochemical Properties in Different Phases of Pig Manure Composting

SIMPLE SUMMARY: China is not only the world’s largest country in terms of livestock and poultry farming, but also the number one country in terms of pig farming. Although the pig farming industry has made great achievements in China, it has also produced a large quantity of waste, generating about 2 billion tons of manure each year, accounting for 47% of total livestock manure. Environmental pollution problems are becoming increasingly prominent. Composting is an important, reasonable, and effective method to deal with manure, and it feeds nutrients and organic substances back into the soil, which can improve soil fertility and promote crop growth. Bacteria are key drivers in regulating ecosystem functions, and understanding the diversity and dynamic changes in bacteria in composting is very important for optimizing compost. This study investigated the bacterial community composition and functional change characteristics in the pig manure composting process and explored the correlation between the bacterial communities and physicochemical properties. These results will provide theoretical support for further optimizing pig manure compost conditions, promoting microbial metabolism, and improving the quality of organic fertilizers. ABSTRACT: Bacteria are key drivers in regulating ecosystem functions, and understanding the diversity and dynamic changes in bacteria in composting is very important for optimizing compost. This study investigated the structure, composition, and function of bacterial communities in alkaline pig manure compost using Miseq sequencing, PICRUSt2. The ACE and Chao1 indices of the bacterial communities in various phases were significantly different. Bacterial communities of alkaline pig compost were different from neutral and acidic swine manure compost, and there were 438 genera of common bacteria in various stages. The main bacterium was the phylum Firmicutes. There were six genera, including Romboutsia, Clostridium, Terrisporobacter, norank_f_Marinococcaceae, Saccharomonospora, and unclassified_f_Bacillaceae, that were significantly correlated (p < 0.05), or even extremely significantly correlated (p < 0.001), with the physicochemical properties. TOC, moisture, C/N, and Tem were the key factors that caused changes in bacterial communities in composting. PICRUSt2 analysis showed that there were seven functional groups: metabolism (45.02–48.07%), environmental information processing (15.25–16.00%), genetic information processing (16.97–20.02%), cellular processes (3.63–4.37%), human diseases (0.71–0.82%), organismal systems (0.66–0.77%), and unclassified (13.93–14.36%). This study will provide a reference for improving bacteria growth and reproduction conditions in pig manure composting, optimizing the process, and improving the efficiency of composting.