Steaming combined with biochar application eliminates negative plant-soil feedback for sanqi cultivation

Eliminating negative plant-soil feedback (NPSF) in agricultural production systems is the key step in maintaining soil health and sustainable crop production. Sanqi (Panax notoginseng) has been severely hampered by NPSF due to the build-up of soilborne pathogens and the accumulation of autotoxic ginsenosides. Steaming on soil followed by adding biochar was investigated. Greenhouse experiments demonstrated that consecutively cultivated soil treated with steaming (90 degrees C for 15 min) significantly increased seed germination rates and seedling survival rates of sanqi, but biochar amendment had no effects. The combination of steaming with biochar amendments (8 g L-1) was more effective on seed germination and seedling survival rates as well as increasing the biomass of sanqi than applying steaming alone. Steaming slightly degraded the content of autotoxic ginsenosides in the soil and completely eliminated the population of soilborne pathogens, including Ilyonectria spp. and Fusarium spp., in consecutively cultivated soil, and enhanced the release of nutritive substances into soil. Biochar showed a high adsorption capacity for autotoxic ginsenosides, and increased nutrient supplementation. Steaming plus biochar could effectively eliminate the negative effects of soilborne pathogens and autotoxicants to P. notoginseng. Four years of field studies further confirmed that consecutively cultivated soil could be successfully replanted after steaming plus biochar application. Thus, steaming plus biochar amendment was a promising practice for enhancing soil quality and health.