Development of soils derived on granitic rocks in South Lampung
1999
Wiharso, D. (Universitas Lampung, Bandar Lampung (Indonesia). Fakultas Pertanian)
Chemical weathering is the weathering process that commonly happened in tropical region. Granitic rocks weather more rapidly by physical weathering than chemical weathering. According to Goldich's Stability Series for minerals, granitic rocks with a high content of resistant minerals should weather more slowly than andesitic or basaltic rocks with a high content of more weatherable minerals. Principally, soil development is the result of horizon differentiation. Degree of soil development is relative and base on soil properties can be observed and measured, also completion of genetic horizon. It is predicted base on soil genesis and morphology. Morphologically, degree of soil development decided base on completion of genetic horizon, and genetically measured base on soil properties relate to their soil genesis; such as ratios of silt to clay fractions, ratios of resistant to non resistant minerals, soil colors, soil and illuviation depth, soil pH, and base saturation. The objective of this research was to study the degree of soil development of soils derived on granitic rocks in South Lampung under humid tropical condition. For this purpose, three profiles of soils derived on granitic rocks in a toposequence in South Lampung were described and samples. Then, soil samples were analyzed, especially for soil properties relate to soil genesis. Based on soil genesis and morphology, three of soil profiles indicated had developed ultimately that were characterized by differentiating to A and B horizons, low of weatherable minerals (10 percent), thick of illuviation horizons, and red color in diagnostic horizons that reached to Hue 2.5 YR in the up and middle slopes. Soil in the middle slope was more developed than the others, then followed by soil in the upper and lower slopes
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