Effect of biochar with microbial agents on enzyme activity in sewage irrigated soil

To investigate the effectiveness of combined microbial agents and biochar in improving enzyme activity in sewage-irrigated soil and promoting plant growth, a pot experiment was conducted using sewage-irrigated soil treated with varying ratios of Bacillus subtilis (BS), Trichoderma harzianum (TH), and corn stover biochar (CSB). The study examined changes in soil enzyme activities and the plant height and aboveground biomass of Festuca arundinacea. The results showed that soil sucrase, phosphatase, and urease activities increased with increasing dosages of microbial agents and biochar, reaching their maximum levels under the T6 treatment (BS (0.5 g/kg) + TH (1 g/kg) + CSB (10 g/kg)). Soil catalase activity exhibited an initial increase followed by a decrease with increasing application rates. Heatmap revealed significant positive correlations among the four soil enzyme activities. At 180 days of cultivation, both plant height (34.28 cm) and aboveground biomass (23.14 g) of tall fescue were significantly highest under the T6 treatment (p < 0.05), markedly exceeding those of the control (CK). In conclusion, the co-application of microbial agents and biochar enhances enzyme activity, plant height, and aboveground biomass in sewage-irrigated soil. The T6 ratio represents the optimal combination identified in this study, demonstrating the significant potential of microbial agents and biochar for improving the quality of sewage-irrigated soils.