Cambodia has an old national soil map at 1:1,000,000 scale, and more recent mapping of rice soils at 1:900,000, but little is known about soil distribution and properties in the uplands. Such soil information is needed to support moves towards crop diversification in Cambodia and the assessment of potential of soils to support production of non-rice crops. This investigation aims to identify the range and distribution of soil types in the Ou Reang Ov District, Kampong Cham Province of Cambodia and to determine the limiting factors of these soils. The capability of these soils to grow maize, soybeans, sesame and mungbeans may then be assessed. The study area is on uplands of mid Pleistocene basaltic flows and associated lowland paddy soils of old and recent alluvium. The uplands are currently dominated by rubber plantations, the lowlands by mixed land use of paddy rice and upland crops.

Soil classification was completed by detailed profile descriptions using FAO descriptors (FAO-ISRIC 1990). These were combined with digital air photos, a digital elevation model and Landsat TM satellite images and expert knowledge to create land unit maps. Chemical and mineralogical properties of the detailed soil profiles have been completed.

In addition to growing field crops in the main wet season (July to October) it is envisaged that field crops will also be grown in the early wet season (April to June) and the dry season (November to April). Key limiting factors relate to waterlogging, physical properties affecting tillage and crop emergence, profile water storage, stoniness and extreme acidity. The move to crop diversification in these upland areas is not only influenced by soils types and limiting constraints, but also by climate, availability of supplementary irrigation and availability of markets to sell produce.