Abstract:The amelioration effects of rice straw, peanut straw and Chinese milk vetch shoot on the acidity of red soil and yellow brown soil from tea gardens were examined with the incubation experiments at three levels of plant materials, i.e., 5, 10 and 20 g/kg added. After the soils incubated with plant materials, soil exchangeable acid and exchangeable Al decreased while exchangeable base cations and base cation saturation increased. For yellow brown soil added with Chinese milk vetch, soil pH increased to some extent compared with control. The amelioration effects of plant materials on soil acidity depend on the ash alkalinity and N content in plant materials. The ash alkalinity and mineralization of organic N increased soil pH, while nitrification of NH4+-N decreased soil pH. The amelioration effect of peanut straw on soil acidity was greater than Chinese milk vetch shoot and rice straw. The incorporation of plant materials into soils resulted in the decline of toxic species of Al obviously in soils, which suggest that the addition of plant materials could alleviate aluminum toxicity to plants in acid soils.