Abstract: Soil acidification is an important factor leading to poor growth and root rot disease of Panax notoginseng in the understorey of forests. In this study, different amounts of quicklime (0, 500, 1000, 1500 and 2000 kg·hm^-2) were amended into acid soil under forest. We evaluated the effect of quikelime addition on soil chemical properties, phenols, rhizosphere microorganisms and growth of P. notoginseng. The results showed that an appro-priate amount of quicklime addition (500-1000 kg·hm^-2) could significantly increase soil pH, decrease the content of phenols (p-hydroxybenzoic acid, vanillin, syringic acid, ferulic acid and vanillic acid), promote P. notoginseng growth, and reduce the incidence of root rot disease. An appropriate amount of quicklime (500-1000 kg·hm^-2) could significantly reduce the fungi:bacteria ratio, increase bacteria diversity, and increase the relative abundance of Ascomycota and Proteobacteria as well as Massilia and Sphingomonas. However, excessive quicklime addition (1500-2000 kg·hm^-2) could reduce the content of available nitrogen and organic matter, and inhibit P. notoginseng growth. Therefore, 500-1000 kg·hm^-2 of quicklime amendment could improve the chemical properties and microbial community of acid soil under forest, thereby promoting P. notoginseng growth, and reducing the incidence of root rot disease.

Key words: quicklime, soil acidification, phenols, microbial community