Abstract: Eighty-six topsoil (0-20 cm) samples were collected from 8 land use types (natural forest land, maize field, tea garden, paddy field, rubber plantation, flax field, banana plantation, and sugarcane field) in the Naban River Watershed National Nature Reserve and its surrounding areas, and the soil physical and chemical properties were analyzed, aimed to study the effects of land use type on the soil quality by the method of soil quality index (SQI). Comparing with natural forest land, all the cultivated lands had somewhat decreased soil organic matter content and higher soil bulk density, and the soil bulk density was significantly higher in tea garden, paddy field, rubber plantation, and banana plantation. In cultivated lands, fertilization and reclamation made the soil available potassium and phosphorus contents maintained at a higher level, probably due to the input of mineral potassium and phosphorus and the decomposition of soil organic matter. The SQI of the 8 land use types was in the order of flax field (0.595)> natural forest land (0.532)> maize field (0.516) > banana plantation (0.485)> tea garden (0.480)> sugarcane field (0.463)> paddy field (0.416)> rubber plantation (0.362). The soils in higher altitude production demonstration areas (1614±115 m) had significant higher SQI, compared to the soils in lower altitude buffer areas (908±98 m) and junction areas (926±131 m). Among the 8 land use types, the rubber plantation in lower altitude areas had the lowest SQI, due to the lower soil organic matter and available potassium and phosphorus contents and the highest soil bulk density. Application of organic manure or intercropping with leguminous plants could be an available practice to improve the soil quality of the rubber plantation.

Key words: land use type, soil quality index, natural forest, rubber plantation, tea garden, paddy field