Abstract: In this study, 38 tea garden and adjacent woodland were chosen in An’xi county to investigate soil pH and nutrient changes. The results show that, soil pH was decreased by 0.031 units per year from 4.81 in woodland to 4.17 in tea garden. Contrast to woodland, the ratio of tea-grown soils with pH 4.0-4.5 and pH<4.0 were increased by 27% and 36.8%, which significantly increased the contents of total exchangeable acid, exchangeable H⁺ and exchangeable aluminum Al³⁺. After the conversion of forest land to tea garden, the contents of soil total nitrogen, hydrolysable nitrogen, available phosphorus and available potassium were increased by 0.29 g·kg^-1, 33.39 mg·kg^-1, 59.06 mg·kg^-1 and 29.75 mg·kg^-1, respectively. Furthermore, the C/N ratio was significantly decreased by 5.67. With the increase of tea planting years in tea garden, the contents of total nitrogen, hydrolysable nitrogen, available phosphorus were increased significantly. The change of soil pH was significantly and negatively correlated with those of soil hydrolysable nitrogen, available phosphorus and available potassium. The average contents of hydrolysable nitrogen, available phosphorus and available potassium would be increased by 63.92 mg·kg^-1, 52.45 mg·kg^-1 and 55.84 mg·kg^-1 when soil pH was decreased by 1 unit. When the environmental threshold is reached, there is a risk of phosphorus pollution to the environment. The survey results show that the tea garden in Anxi County needs to increase the input of organic fertilizer and carry out targeted formula fertilization to slow down the acidification trend of soil.

Key words: woodland, tea garden, soil acidification, chemical properties