Ultisols under upland farming practices in Lower Northern Thailand with special reference to long-term productivity

摘要

This study evaluated the influences of various land uses on mineralogical properties and charge characteristics, and discussed the availability of these properties as a tool that can assess the potential of the soils in terms of long-term productivity. Thirty study sites, which are located in the upland area of Lower Northern Thailand, were selected including cropping lands and fallow forests under shifting cultivation systems (maize and cassava), fruit and mixed tree plantations (e.g., mangoes (Mangifera indica) and longan (Dimocarpus longan)) and natural forests (dry evergreen forest with Irvingia malayana and Pterocarpus macrocarpus). Soil samples were collected from the surface and subsurface layers before and after burning practice. Most of the soils in the village were classified into Typic Paleustults. The soil fertility level widely varied among land use types. The PZSE values were constant irrespective of land use types. Whereas sigma p values was not related to land use types. Kaolin minerals were predominant among clay minerals in the study area associated with occurrence of weatherable 2:1 type clay minerals. The conventional chemical properties were affected by burning practice. On the other hand, sesquioxide properties and clay mineral compositions did not change by burning practice. The conventional measurements are useful for assessment of the current crop management. While the use of the charge characteristics and mineralogical properties seem to be beneficial to evaluate long-term productivity, because these properties are rather stable against the impact of various agricultural practices..