Characteristics of soils derived from ultramafic rocks in Homonhon Island, Philippines

photo0091Miguel Francisco B. Abulencia and Faustino P. Villamayor, 2013 *( 


The prevalence of mining activities in Homonhon Island, Philippines has affected the soil resources and the agricultural livelihood of the people in the island. Thus, this study aims to determine the physical and chemical properties of the soils and recommend suitable tree species for revegetating the area.

Five pits representing specific positions in the hillslope (i.e., summit, shoulder, backslope, footslope, and toeslope) were selected and representative soil samples from each horizon of the pit were collected for analyses following standard procedures.

Soils have pH values ranging from 5.5 – 6.8 and low potential CEC values of <34 cmol(+)/kg with the presence of kandic horizon in all soils except for the backslope which has cambic horizon. Moreover, soils generally have decreasing organic matter content and available P with increasing depth. All the soils except for the backslope are classified as Kandiudults while the backslope qualified as a Dystrudept.

Acid-tolerant species such as Piliostigma malabaricum is suitable in the area. Morover, no-tillage and or contour hedgerow can be applied in the hillslope so as to minimize soil erosion. Addition of organic materials through green manuring is beneficial as it does not only promote aggregation but also serve as a source for nutrients.

keywords: ultramafic rocks, mining activities, Piliostigma malabarcium


Comparison of soil degradation processes in selected degraded uplands in Samar island

IMG_4967Dernie T. Olguera* and Victor B. Asio, 2013 *(


This study evaluated the dominant soil degradation processes in selected degraded uplands of Samar Island, determined the important factors influencing soil degradation in the selected sites and identified the indicators of soil degradation.Two (2) sites were selectedin Sta. Rita, Samar and Salcedo, Eastern, Samar representing the western and eastern sides of Samar Island respectively, were selected.

Soil erosion is the major soil degradation process in the degraded upland studied. It resulted not only in considerable soil losses but nutrient losses as well. Soil erosion varied with vegetation cover and site. It was much higher in the sweetpotato, cassava, and gabi crops than under natural vegetation. In addition, soil erosion was higher in Salcedo than in Sta. Rita which is related to climatic and soil characteristics. Bulk density, porosity, aggregate stability, soil pH, organic matter, and carbon dioxide evolution are good indicators of soil degradation. Dominance of Saccharum officinarum, Imperata cylindrica, Melastoma affini and Psidium guajava indicated degraded soil condition. Farmer’s practices particularly clean culture and organic fertilizer application influenced the degree of soil degradation.

Keywords: soil degradation, soil erosion, degraded uplands, Samar Island

Nutrient status of selected degraded upland soils in Samar island

IMG_4925Leo Jude D. Villasica* and Victor B. Asio, 2013 *(


Due to the low productivity of degraded uplands, this study focused on the evaluation of the nutrient status of two degraded upland soils in Samar island namely, Brgy. Tulay, Sta. Rita, Western Samar and Brgy. Naparaan, Salcedo Eastern Samar. Soil monitoring plots were established in the farmer’s field planted to various crops. The soil nutrient status was evaluated by periodic sampling and analysis of the soil pH, OM, total N, available P, exchangeable bases, readily mineralizable C and N, plant nutrient concentration and microbial activity by soil respiration.

Results revealed that the nutrient status of the degraded uplands in Sta. Rita and Salcedo are low. In general, the low nutrient status is more severe in the Salcedo site than in the Sta. Rita site which is related to the more weathered nature of the former than the latter. Moreover, both sites have strongly acidic soil which is low in OM, total N, available P, and exchangeable bases contents. The low nutrient status of the soil is reflected by the low leaf concentration of the nutrients (N, P, K, Ca). Also, the low nutrient status is observable from the low respiration rate and low levels of readily mineralizable C and N. Considerable variations in nutrient status is observable under different vegetation covers.

Keywords: nutrient status, degraded uplands, vegetation cover, Samar Island