Biochar derived from rice husk: Impact on soil enzyme and microbial dynamics, lettuce growth, and toxicity

This study was set to investigate the effects of rice husk biochar (RHB) on soil characteristics and growth of lettuce (Lactuca sativa). A comprehensive research approach was employed to examine the effect of different RHB concentrations (i.e., 0–1.5%) on soil pH, soil enzyme activities (i.e., alkaline phosphatase, beta-glucosidase, and dehydrogenase), soil microbial community, lettuce growth, and earthworm toxicity. The results showed that, within the studied RHB concentration range, the RHB application did not have significant effects on the soil pH. However, the enzyme activities were increased with increasing RHB concentration after the 28 d-lettuce growth period. The RHB application also increased the abundances of the bacterial genera Massilia and Bacillus and fungal genus Trichocladium having the plant growth promoting abilities. Furthermore, the study revealed that the root weight and number of lettuce leaves were significantly increased in the presence of the RHB, and the growth was dependent on the RHB concentration. The improved lettuce growth can be explained by the changes in the enzyme and microbial dynamics, which have resulted from the increased nutrient availability with the RHB application. Additionally, the earthworm toxicity test indicated that the tested RHB concentrations can be safely applied to soil without any significant ecotoxicity. In conclusion, this study underscores the potential of RHB as a soil amendment with positive effects on crop growth, highlighting the utilization of agricultural byproducts to enhance soil biological quality and plant growth through biochar application. © 2023 Elsevier Ltd