Chemical degradation of a Ferralsol (Oxisol) under intensive rubber (Hevea brasiliensis) farming in tropical China

Impacts of intensive management practices on rubber (Hevea brasiliensis) farms (e.g., land clearance, fertilization, and rubber tapping) have not been adequately investigated. In this study, soil was taken from fields of grass (before rubber plantation), immature rubber (before tapping), and mature rubber (after tapping) at a tropical farm in Hainan, China. Soil organic matter, plant nutrients, cations, and soil pH were determined. Rubber cultivation resulted in significant decline of soil organic C and microbial biomass C. Available P was extremely low for all soils, resulting from the naturally low P content and the high sorption capacity of highly weathered Ferralsol. Furthermore, soil pH decreased by about 0.5 units, accompanied by an increase of exchangeable Al by more than one-fold. Regression analysis demonstrated that soil acidification was characterized by the depletion of base cations and release of Al. To maintain tropical soil quality, farming practices such as liming and organic amendment should be included in the best management practices of rubber farm.