Smectite under heavy clay soils development at FRE Wanagama forest area

A degraded area in Forest Research and Education (FRE) Wanagama 1 was successfully rehabilitated with Gliricidia sepium, a fast growing pioneer species capable of producing a great amount of organic matter, and which facilitates the development of a shallow clay soil. Since rehabilitation, this area has received minimal human disturbances, and is thus a suitable area for studying soils developed on/or in association with limestone parent material. Such studies, which are rather limited, contribute to knowledge on soil development in the tropics. Soil samples from six plots representing two different stand ages (44 and 28 years old) of G. sepium, three slope positions, and soil depths were collected and analysed for selected physical, chemical and mineralogical properties. Results of this study showed that the soil is dark brown to very dark grey in color, contains a high amount of organic matter, is pH neutral to alkaline and is dominated by clay particles which mainly consist of smectitethe soil can therefore be classified as Vertisols. The smectite-dominated soil is developed from dissolution and subsequent precipitation of limestone parent materials. Soil forming factors, namely monsoonal climate, dense vegetation which causes builtup of soil organic matter content, and terracing were responsible for the formation processes