Abstract
Dark reddish brown colored Latosol is found on the upper part of basalt plateau (about 70m above sea level) in Khet Kompong Cham, Cambodia. At the middle and lower parts of the plateau occur "Degraded dark colored soils with pisolite". The climate of this region is tropical one with well defined rainy and dry seasons, precipitation is about 1600mm. This soil has dark reddish brown color throughout horizons, but the A horizon is slightly darker than the B horizon. The soil has characteristically heavy texture (heavy clay), and contains some "buck-shot" iron concretion (goethite). The pH (H_2O) is 6.10 in the A, 4.83 in the B horizon, and pH (KCl) is 5.30, and 4.03, respectively. As compared with other Latosols this soil has rather high organic carbon contents; 2.68% in the A, 1.08% in the B horizon. This soil has, except for the A horizon, very low CEC and base saturation and small amount of exchangeable Ca and Mg. The SiO_2/Al_2O_3 ratio of fine earth is very narrow, and nealy equal to that of clay. Low SiO_2/Fe_2O_3 ratio indicate the residual concentration of iron due to severe lateritic weathering. Clay mineral in this soil is mostly well crystallized kaoline mineral, with traces of hematite, but gibbsite was not detected. From the results, this soil is interpreted to be Dark reddish brown Latosol which has suffered severe lateritic weathering for long time under tropical climate.
