Biochar Reduces Generation and Release of Benzoic Acid from Soybean Root

Plants can generate and release allelochemicals into soils under environmental stresses to compete for resources and to combat pathogens and parasites. The frequent rotation of cultivated land and the high-density cropping may result in the accumulation of allelochemicals, resulting in obstacles to continuous cropping. Biochar has been proven to improve soil quality, which can potentially reduce the formation of allelochemicals by plants, alleviating allelopathy. In this study, the formation of an allelochemical substance benzoic acid (BA), the growth indicators, and root lipid peroxidation of soybean were investigated under the influence of biochar application in soils through pot experiments. A reduced BA content was observed in the soils after biochar application, and sorption and degradation of BA by biochar could not explain this change. BA contents inside and outside the soybean root also decreased after the addition of biochar, indicating a significant reduction in BA formation by the plant. The reduced lipid peroxidation (malondialdehyde (MDA) concentration) in soybean roots and promoted plant growth indicated that biochar application greatly reduced plant BA stress. Therefore, biochar addition into the soil can reduce the generation and release of BA from soybean root, which has a positive effect on alleviating allelopathy. This study provides a new angle for a comprehensive evaluation of the environmental impact of biochar and technical support for overcoming the obstacles in continuous cropping.