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Relationship between parent materials and soil pH on Venezuelan Andean soils

Abstract:

Soil reaction in water was measured and analyzed for 502 Soil profiles localized in five geologic areas of the Venezuelan Andes, between 1000 and 4000masl. The pH of the soil solutions can be estimated from the characteristics of the geologic materials in the area. Soils are generally acid regardless the rainfall variations. This soil property is the result of the parent materials present in the area, which are mainly formed by shales, phyllites, quartzites, granites, and quartz-schists, among others, with low contents of alkali elements. There is not a constant, direct or inverse relationship between the soil classification at Order level and the soil pH. The soil orders Ultisols, Entisols and Inceptisols show similar reactions, while the reaction of Mollisols are not acid, due to human activities and parent material.