To understand the genesis of soils derived from a late Quaternary sedimentary rock in Leyte, Philippines, the properties of four soil profiles were investigated. Two of the profiles (PS-1, PS-4) derived from coralline limestone were shallow with less developed horizons and alkaline pH conditions and higher potential cation exchange capacity and are classified as Calcaric Phaeozems in the World Reference Base or fine, calcareous, isohyperthermic, Rendollic Eutrudepts in Soil Taxonomy. The other two profiles (PS-2, PS-3) derived from calcareous shale were deeper with well-developed horizons and characterized by high loss of bases and were classified as Haplic Alisols (Hyperdystric, Rhodic) or fine, kaolinitic, isohyperthermic, Typic Hapludalfs. The calcareous shale parent materials have much faster weathering as shown by the higher clay content and the dominance of kaolinitic and halloysitic clay minerals. In those soils developed from limestone, clay minerals were mostly calcite, smectite, vermiculite, and interstratified kaolinite/smectite. The results of this study suggest a strong influence of external material contributions, particularly volcanic-ash deposition on the progression of the soils, as reflected by higher clay and silt contents in these comparatively young soils. The most important pedogenic processes that formed the soils in the area seem to be weathering and clay formation, loss of bases and acidification, inorganic C accumulation, structure formation, desilication, and ferrugination. The nature and characteristics of the parent material, topography, and the time of pedogenesis also have assertive effects on the development of the soils.
1United Graduate School of Agricultural Sciences, Iwate University, 3-18-8 Ueda, Morioka, Iwate 020-8550, Japan. Dr. Ian A. Navarrete is corresponding author. E-mail: email@example.com
2Laboratory of Environmental Soil Science, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho 080-8555, Japan.
3Department of Agronomy and Soil Science, Visayas State University, Baybay, Leyte, 6521-A, Philippines.
Received August 25, 2010.
Accepted for publication August 23, 2011.
Financial Disclosures/Conflicts of Interest: None reported.