Victor B. Asio, Kier Lambert B. Demain, Dernie T. Olguera and Leo Jude D. Villasica
The study evaluated the morpho-physical, chemical, and biological characteristics as well as the nutrient status of two degraded upland soils located in Sta. Rita, Western Samar and in Salcedo, Eastern Samar. Soil profiles were examined and soil erosion was determined. Composite soil and plant tissue samples were collected from different vegetation cover or crops planted by the farmers. All laboratory analyses were done following standard procedures. Results indicate that: 1) the Sta. Rita soil which is relatively younger than the Salcedo soil shows less severe degree of degradation than the Salcedo soil; 2) the nutrient status of the degraded upland soils in Sta. Rita and Salcedo are low; 3) the low nutrient status is more severe in the Salcedo than in the Sta. Rita; 4) both sites have strongly acidic soils which are low in OM, total N, and available P contents; 5) considerable variations in the soil nutrient status were observed under different vegetation covers or crops; 6) soil erosion the appears to be major soil degradation process in both degraded uplands; 7) the low nutrient concentrations in the tissues of the plants growing at the sites reflect the low nutrient status of the soils; and 8) bulk density, porosity, aggregate stability, soil pH, organic matter, and carbon dioxide evolution appear to be good indicators of soil degradation.
Keywords: soil degradation, soil formation, shale, ultramafic rock, soil erosion