Unearthing the mechanisms underlying calcium carbonate therapies for eliminating pathogens during composting

The elimination of pathogens during composting is crucial for safe utilization of organic fertilizers and food security. Nevertheless, simple, low-cost and eco-friendly techniques for pathogen elimination are extremely scarce. The current study was aimed to explore mechanisms underlying the effects of calcium carbonate (CaCO3) addition on pathogen elimination during composting. High throughput sequencing and metabolomic analysis were adopted to determine the efficiency of CaCO3 in pathogen elimination. CaCO3 addition significantly decreased the abundance of pathogens along with increased temperature, pH, electrical conductivity, and extracellular enzyme activities of composting. CaCO3 strongly changed fungal community composition and increased fungal Shannon index and Phylogenetic diversity at the mesophilic phase with Shannon index positively related to pathogen abundance. The fungal function of Plant Pathogen significantly decreased at the thermophilic phase under CaCO3 addition. Antipathogenic metabolites were significantly increased under CaCO3 addition, including 8-iso Prostaglandin F2-Ethanolamide from Fatty acids degradation, Xanthium, 5-(3,4-dihydroxybenzylidene) hexahydropyrimidine-2,4,6-trione and Evernic acid from Aromatic amino acids metabolism, which were responsible for the elimination of Fusarium, Erysiphe, Colletotrichum, Pseudocercospora, Pythium, and Verticillium at the thermophilic phase. Our findings demonstrate that CaCO3 addition could efficiently eliminate pathogens during composting, so that benefit agricultural disease control and food security.