Objective  The aims were to clarify the soil fertility status of tea plantations in Lincang, Yunnan Province, in order to provide scientific basis for soil nutrient management and yield/quality improvement of tea.

Methods Fresh tea leaves and 0 - 30 cm soil samples were collected from ancient tea plantations and terrace tea plantations in Lincang, Yunnan. Soil nutrient contents and basic quality indicators of tea leaves were determined. Based on tea plantation soil nutrient grading standards, the integrated fertility index (IFI) of soil was obtained by combining membership degree and principal component analysis. Combined with correlation and random forest analysis, comprehensive evaluation was conducted on soil nutrients of ancient and terrace tea plantations in Lincang.

Results Results showed that tea plantation soils in Lincang had suitable pH and abundant organic matter, available nitrogen, available potassium, available iron and available manganese, but were deficient in exchangeable calcium and magnesium, and available phosphorus, sulfur, copper, zinc, boron and molybdenum, with deficient sample proportions ranging 25.93% - 98.11%. Ancient tea plantations had significantly higher available sulfur, boron and molybdenum than those in terrace tea plantations, with less severe medium/trace element deficiencies. The IFI of tea plantation soils in Lincang ranged 0.26 - 0.82, generally at medium to relatively high levels, where IFI of both ancient and terrace tea plantations was greatly affected by available phosphorus and zinc, and exchangeable calcium and magnesium. Soil IFI showed significant positive correlations with amino acids and caffeine in tea leaves.

Conclusion Tea plantation soils in Lincang generally have medium or above-medium fertility levels, but phosphorus and medium/trace elements should be supplemented during management.