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

Increasing degree of soil compaction affects the growth and yield of sweetpotato cultivars

kamote1Ariel B. Bolledo*, Sergio M. Abit, Beatriz C. Jadina, 2011 *(


Influence of soil physical factors like soil compaction has been known to affect root growth and tuberous root development of sweetpotato.  This physical factor is often left-out in the evaluation of newly released cultivars of sweetpotato.  A pot experiment was conducted to evaluate the growth and yield responses of sweetpotato cultivars to various levels of soil compaction and to determine the degree of soil compaction that would result in optimum growth of various sweetpotato cultivars.  A 4 x 3 factorial experiment with 4 sweetpotato varieties (PSB SP-16, PSB SP-17, PSB SP-25 and Ciete Flores) as factor A under 3 levels of compaction (1.1, 1.3 and 1.5 g cm-3 bulk density) as factor B was conducted.  Results showed that depth of tuberous root formation and number of marketable tuberous roots decreased with the increasing degree of soil compaction.  Other growth and yield parameters were not significantly affected by the treatments applied.  Interaction effect of sweetpotato cultivars and levels of soil bulk density was significant on depth of tuberous root formation and number of marketable tuberous roots.  Observation on the nature of formation, penetration, distribution and direction of tuberous root development showed that those at lower degree of compaction (1.1 g cm-3), tuberous roots were evenly distributed and were able to penetrate vertically and formed at deeper parts of the soil layer.   However, the tuberous roots in compacted soils (1.3 to 1.5 g cm-3) were formed at shallower depths andwere not able to penetrate deeply.

Keywords: Compaction, Bulk Density, Sweetpotato cultivars, Tuberous root formation,

Physical and chemical characteristics of soils from the landslide areas of Abuyog, Leyte

DSC09705Jorge P. Cabelin* and Beatriz C. Jadina, 2013 *(


The steep and unstable topography of Abuyog, Leyte and recent landslide occurrences in the area particularly in Canmarating and Tadoc justifies the need for soil characterization of the landslide areas of the place. This research was conducted to determine the physical and chemical properties of soils from the landslide areas in Abuyog,  Leyte and relate these to landslide occurrences.  Two landslide cuts from different sites were evaluated using representative soil profiles which were examined in the field and sampled for the analysis of physical properties including particle size distribution, bulk density, particle density, total soil wet density, porosity, field capacity and water holding capacity, hydraulic conductivity, Atterberg limit and some chemical properties including pH, organic matter content, cation exchange capacity, and exchangeable sodium content.

Soils from the two landslide areas in Abuyog, Leyte generally have clayey texture, low bulk density, high total soil wet density, average particle density, porosity, moderately high saturated hydraulic conductivity, high liquid limit, and plastic index with very strongly to moderately acidic pH, high organic matter in surface and low at subsurface layers, moderate CEC and exchangeable Na.

Keywords: landslide, physical, chemical, plastic limit, Atterberg limit