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Pedological Characteristics of soils in Mount Mayon, Albay, Philippines
Dissertation Abstract:
The study was conducted to establish the nature of soil development of different soils in Mount Mayon. The frequent eruption of Mount Mayon did not pose hindrance to having a detailed analysis of its soils. Based on the history of Mayon eruption, time of deposition of parent materials, and type of volcanic materials, 11 pedons were excavated around Mount Mayon to morphologically, physically, chemically, and mineralogically characterize and classify the soils of the representative pedons. The different pedons were located in the different land surface units. The 11 soil pedons were classified as Humic Pachic Dystrudepts (pedon MVA1), humic Dystrudepts (pedons MVA2. MVA3, MVA4, MVA5, MVA9, and MVA10), Vitrandic Eutrudept (pedon MVA6), Humic Psammentic Dystrudepts (pedon MVA7), Aquic Eutrudepts (MVA8), and Vitrandic Udorthents (pedon MVA11).
The unconsolidated debris and materials from eruption, colluvial, and alluvial additions were the parent materials of the soils in the 11 pedons. The magma composition was predominantly plagioclase, hypersthene, and augite, thus the rock type of the parent material was hypersthene-augite Andesite. The very high amount of easily weatherable primary minerals such as hypersthene and augite (pyroxenes), and slowly weatherable primary minerals such as plagioclase indicated that weathering of these primary minerals was not intensive. The cumulization due to eruption, colluvial, and alluvial additions, combined with high rainfall, warm and humid conditions favored the enrichment, littering, ripening, humification, melanization, eluviation and illuviation, and braunification pedogenic processes on higher land elevation, whereas decomposition and pedochemical weathering such as oxidation-reduction cycles in pedon represented the major pedogenic processes in rice field on alluvial toe slope with shallow water.
The Mayon soils have not undergone prolonged pedogenic processes because soil development was limited to (1) darkening of the surface horizons in the most recent developed soils (pedons MVA2, MVA3, MVA4, MVA6, MVA7, MVA9, and MVA11); (2) certain degree of B horizon formation and illuviation of clay but not enough to form argillic horizon in soils that represent intermediate developed soils (pedons MVA1, MVA5, and MVA8); and (3) certain degree of horizonation and deep solum in soils that represent the more advanced developed soil (pedon MVA10).