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Toposequence of Soil on Diorite Mountain in Benguet, Philippines
Dissertation Abstract:
The study determined the morphological, physical, chemical, and mineralogical properties of the soiI on diorite mountain in Benguet, Philippines. The soil properties were used to compare the soil on seven land surface units of a hillislope. These were the interfluve, seepage slope, convex creep slope, fall face, transportational midslope, colluvial footslope, and alluvial toeslope. All the soil studied were classified based on the Soil Taxonomy, United Sates Department Agriculture (USDA) Soil Classification System.
The genetic relationship of soils is a function of topography. Soils in different positions on hillislopes are related to each other by translocation and accumulation process. The weathering of parent rock have been rapid and enhanced by the warm and humid climate, good drainage, and slope of the mountain area. Several pathways of mineral formation have probably occurred depending on the weathering environment.
Results of the study showed that soiIs in the intertluve and seepage slope were old and showed well-developed profiles. The soils were classified as Typic Hapludults, Typic Kandihumults, and Fluventic Dystropepts. SoiIs in the convex creep slope had experienced continuous losses of surticial material while that in the fall face were lost due to mass movement. Both land surface units showed less profile development. Soils in the convex creep slope were classified as Typic Troportents while that in the fall face was classified as Typic Troportents.
SoiIs at the transportational midslope had very deep, well-developed protile and showed lithologic discontinuity. Soils were classified as Typic Haplohumults and Fluventic Dystropepts. Soils at the colluvial footslope and alluvial toeslope had less protile development. Soils in the colluvial foots lope were classified as Fluventic Dystropepts and Typic Tropotluvcnts while that in the alluvial toeslope was classified as Fluventic Dystropepts. The soils studied had mixed mineralogical composition. The ability of these soils to hold and exchange nutrient cations was primarily dependent upon their organically-enriched surface horizon. The mineral fraction appeared to contribute little to cation exchange. Low levels of nutrients, low organic matter, very low avaiIable phosphorus below the surface, and aluminum toxicity were the problems of these soils. To overcome such problems, the following steps should be considered: 1) maintenance of organic matter for the supply of nutrients; 2) addition of fertilizer with emphasis on application of phosphorus; 3) judicious liming to neutralize the exchangeable aluminum; and 4) adoption of appropriate cropping system and soil conservation practices for each specific land surface unit.