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The Caldenal soils receive residues that vary in quantity and quality, according to the dominant vegetation. The aim of this work was to analyze the influence of the vegetation on the edaphic properties of the soil. An Entic Haplustoll was sampled by patches with the predominance of forage species (F), non forage under Calden (NF) and shrub (A). Fractions of organic carbon, total nitrogen, available phosphorus, exchangeable cations and hydro phobicity and infiltration parameters were determined. The NF soil presented high contents of total organic carbon and its fractions and also a high level of total nitrogen and phosphorous availability. In the F soil was found that the apparent density was higher and the exchangeable calcium content was lower. The surface of the soil in the F patch was classified as slightly water repellent, while the other soils' surfaces were strongly repellent. The medium infiltration rate was lower for the NF patch soil and higher for the A patch soil, which had the highest final infiltration rate. Soil studies in the Caldenal are recommended to be realized with an experimental design that allows controlling the variability that the dominant vegetation causes on the surface, due to the influence that vegetation has on the edaphic properties of the soil. [ABSTRACT FROM AUTHOR]

Eolian parent materials of soils of the semiarid Argentinean Pampas show high volcanic ash contents. Weathering products of volcanic ashes can sorb anions in many soils. The objective of this study was to analyze the volcanic ash distribution in soils of the semiarid Pampas,its weathering state, and the influence of its weathering products on phosphate sorption. Sixteen soils, classified as Entic Hapludolls and Entic Haplustolls, were studied at different landscape positions of five sites placed in a SW-NE-oriented climosequence within the semiarid Pampa. Results showed that volcanic ashes accumulated more in the subsoil of SW-placed profiles and in the topsoil of NE-placed profiles. Topsoil accumulated ashes of NE-placed profiles were deposited by the eruption of Quizapu volcano in 1932. Subsoil accumulated ashes of SW-placed profiles were deposited by older volcanic eruptions. Acid oxalate soluble Al(Alo), an index of the degree of volcanic ash weathering, was higher in the subsoil of profiles placed at the SW extremity of the sequence. The larger effect of ash age rather than climatic conditions on ash weathering rate was deduced. Allophane contents were low in all soils (<0.8%). Prevailing clay minerals were illite and very low crystallized intergrade illite-sinectites. Soils with the highest volcanic ash content also held the largest amounts of illite-smectite intergrades. Alo contents explained 52% of sorbed phosphates, and only 36% of fixed P. By including the contents of exchangeable Ca2+ and CaCO3 into the model, 73% of sorbed P variations and 58% of fixed P variations were explained. No measurable effects of volcanic ashes on phosphate dynamics are expected to exist in soils placed to the north of the studiedregion, but in soils placed to the south, which have high contents of CaCO3 and exchangeable Ca2+ , amorphous volcanic ash, weathering products can retain large amounts of phosphates. [ABSTRACT FROM AUTHOR]