Origin and Properties of Deep Sands of Southeastern Cambodia: Some Preliminary Findings

Abstract

Deep sandy soils are a feature of many landscapes in Southeast Asia but the explanations for their origin are not always known. Deep sand and sand on clay profiles cover a large proportion of Cambodia. These soils are commonly used for rainfed rice production, but increasing attention is turning to their potential for crop diversification in the uplands of Cambodia. We examined the origin of 19 sand profiles in southeastern Cambodia particularly to differentiate them in terms of properties that pose constraints for the management of upland crops. From texture analysis along four toposequences including Kampot, Tram Kak, Ponhea Kraek, and Rolea Bíer/Tuek Phos (Kampong Chhnang Province) districts, the sand fractions ranging from 63 to 200 μm and 200 to 600 μm were predominant in most profiles, except for Kampot 4, where sand grains were predominantly from 200 to 600 μm and five profiles from Kampong Chhnang Province, where the three coarse sand fractions (63–200, 200–600, and 600–2000 μm) were equally prevalent. Clay content was generally <100 g/kg within 0–80 cm depth but increased from 80 to 100 cm depth. Subrounded sand grains were more prevalent in the profiles in the lower part of the toposequence. The sand profiles sampled along toposequences in four study areas of south-east Cambodia showed a major influence of in situ weathering of siliceous parent materials and to a lesser extent of colluvial transport of sands. There was no evidence of long-range transport of the sand grains or aeolian processes in the sands.