Effects of different exogenous additives on humification and microbial community during tomato straw composting process

This study investigates the effects of biochar, phosphogypsum, and calcium superphosphate on composting tomato straw to improve compost quality and reduce composting time. Four treatments were tested: T1 (tomato straw + 0.5% EM bacterial agent), T2 (tomato straw + 10% biochar + 0.5% EM), T3 (tomato straw + 10% superphosphate + 0.5% EM), and T4 (tomato straw + 10% phosphogypsum + 0.5% EM). Results showed that these additives extended the high-temperature phase and improved compost maturity, with T2 being the most effective. T2 exhibited the highest increase in humic acid (127.01%) and the greatest degradation of organic matter (63%) and cellulose (69.82%), outperforming the control (p < 0.05). Microbial analysis revealed that Firmicutes , Actinobacteriota , and Proteobacteria dominated the phylum level, while Bacillus, Weissella, Staphylococcus, and Halocella were key genera. Corynebacterium was identified as the main microorganism responsible for spoilage and maturation. This study highlights biochar’s role in enhancing humification in tomato straw composting.