Investigation of acidification and changes in mineral element concentrations of Guizhou yellow soils in long-term tea plantations

This study aimed to investigate where acidification occurred in soil profiles of Guizhou tea gardens, in addition to the influence of acidification on the availability of soil mineral elements in order to inform soil nutrient management and improvement practices in tea gardens. Important tea-producing areas of Guizhou were investigated in this study and samples were collected from tea gardens with similar soil parent material and management measures. The acidification characteristics were investigated in soils from plantations grown for various numbers of years and across different soil layer profiles. Moreover, the pH buffering capacities (pHBC) of soils were evaluated and changes in soil Fe, Mn, Cu, Zn, Mo, B, As, Pb, Cr, and Cd concentrations due to soil acidification were explored. With increased tea plantation age, the acidification rate of 0–20-cm soil layers reached 0.025 pH unit/year. Soil acidification extended from the surface layer downwards through profiles, while the pH of entire soil layers were < 4.5 after 40 years of tea plantation. The pHBC of soils were < 30 mmol/kg, remaining at a weak sensitive level. Fe, Mn, Cu, Zn, Mo, and B concentrations exhibited decreasing trends in soils, while As, Pb, Cr, and Cd exhibited enrichment at the surface. Tea plantation age and soil depth were significantly correlated with the available concentrations of soil mineral elements. Soil acidification gradually increased downward from the surface and soil minerals were lost in acidic environments, while the acid buffering capacity was reduced. These results suggest that organic fertilizers and trace elements should be supplemented as needed in the management of tea gardens to achieve long-term stability of quality and yields.