Soil Survey for Land Resource Management for Agriculture and Forestry in Small Watershed

Abstract

Soil surveys at Wat Chan and Kae Noi Watersheds, Chiang Mai province were carried out during April 1992 to April 1994. The semi-detailed reconnaissance scale 1: 15,000 was applied in which air photo-interpretation and field observations (free surveys) were made by the surveyors. Soil characteristics were studied and classified from order to family levels. From the soil survey results, it was found 6 mapping units (great group/and associations of great group) at Wat Chan and 5 mapping units at Kae Noi watersheds. These soils can be classified in 3 orders, 6 suborders, and 8 great groups. Morphological features of soil observed in the field at all localities are not largely different, weathering in situ from various rocks, generally deep to very deep and well drained soils (except those in the valley bottom which have imperfectly drained). Upper soil horizons are sandy loam to clay, dark grayish brown to dark reddish brown, lower soil horizons are sandy clay loam to clay, dark brown to red. Most of the soils under investigations have a medium fertility status. Due to its topography, slope is the major limitation for permanent agricutural land used. It should be conserved as watershed areas and forestry resources. With conservation techniques, permanent agriculture could be established sucessfully on the slope lower than 35%.