Abstract:
Clarifying the nutrient status and heavy metal content of soil in organic tea gardens can provide a scientific basis for soil nutrient management, fertility improvement, and ecological risk warning in organic tea plantations. In this study, soil samples were collected from 72 organic tea plantations in seven major tea-producing townships in Simao District, Pu'er City, Yunnan Province; the contents of eight heavy metals, including chromium, lead, arsenic, zinc, copper, mercury, cadmium and nickel were determined; and six soil nutrient parameters, including soil pH, organic matter, total nitrogen, available phosphorus, available potassium and cation exchange capacity were analyzed. The results showed that the average value of soil pH of organic tea plantations in Simao District is 4.44, and 37.5% of soils are in Grade I quality standard. The indexes of organic matter, total nitrogen, and available phosphorus of soils are higher than the quality standard. Furthermore, the application of the soil Integrated Fertility Index (
IFI) for the comprehensive evaluation of soil nutrient status and fertility quality revealed that the
IFI value ranges from 0.25 to 1.00 with an average of 0.66, 22.2%, and 68.1% of the tea gardens soils belongs to Class I, II quality standard, and the excellent rate is 90.3%. The average levels of Cd, Cu, Pb, Cr, Hg, As, Zn, and Ni in the soil are 0.14 mg∙kg
−1, 13.8 mg∙kg
−1, 16.4 mg∙kg
−1, 39.5 mg∙kg
−1, 0.03 mg∙kg
−1, 14.3 mg∙kg
−1, 38.4 mg∙kg
−1, and 16.0 mg∙kg
−1, respectively. The maximum and minimum values of Hakanson potential ecological risk index (RI) are 245.0 and 46.3 respectively, and the mean value is 91.2 (<150). The overall soil nutrient status of the organic tea gardens is excellent with a high IFI for soil fertility and a low RI for potential ecological risk though some areas have serious soil acidification.