Interaction of soil pH, organic matter, exchangeable acidity, and cation exchange capacity in a managed tea farm

The average soil pH value, exchangeable Al³⁺ content, and exchangeable H⁺ content were 4.50 (ranging from 3.95 to 5.88), 6.11 (0.04 to 9.32) cmol kg^-1, and 0.30 (0.03 to 0.62) cmol kg^-1, respectively. The surface soil acidification is severe, and the exchangeable acids in the tea garden were mainly exchangeable Al³⁺. The surface soil of the Yangai tea farm had a high ability to keep and supply fertilizer due to its enriching SOM content (average 55.94g kg^-1) and soil CEC (24.06 cmol(+) kg^-1). Surface soil exchangeable acid and CEC contents were higher after spring tea picking than before spring tea picking in the Yangai tea farm, while their SOM content was just the opposite. Therefore, it was recommended to supplement organic fertilizers after tea-picking because the surface SOM of the Yangai tea farm would decompose and be consumed more during the spring, summer, and autumn tea-picking periods than in winter. In addition, the SOM contents and soil pH values decreased and then increased with the increasing soil depth of the soil profile in three land-use types. The soil acidification rate of the managed tea garden was faster than that of the unmanaged tea garden and <i>Pinus massoniana</i> forest, and the difference in the acidification rate between the unmanaged tea garden and <i>Pinus massoniana</i> forest was slight. Therefore, there should be attention to preventing excessive soil acidification in the later tea garden management.