Abstract

BLANCO, María del Carmen; DIAZ, Silvana Letisia  and  AMIOTTI, Nilda Mabel. Geodisponibilidad de Co, Cr, Fe, Mo, Ni y Zn en la cuenca Aº El Divisorio. Cienc. suelo [online]. 2017, vol.35, n.1, pp.161-170. ISSN 1850-2067.

In the southern Pampa region, soil mineralogy developed on loess and loess-derived sediments presents a high reserve of weatherable minerals, which is associated to an adequate provision of macro and micronutrients. The objective of this work was to quantify total Co, Cr, Fe, Mo, Ni and Zn contents of El Divisorio stream basin (Buenos Aires), to analyze the influence of the geomorphological position and the pedogenetic processes on its inter and intrapedonic variability. Two toposequences were selected in the upper and lower basin. In seven soil profiles, 36 soil samples were collected to quantify these microelements (ACTLABS; INAA). Zn (190-50 ppm) and Cr (70-31 ppm) had the highest intrabasin variability whilst Co (7-19 ppm), Mo (1-3 ppm) and Ni (18-20 ppm) did not have a wide inter nor intrapedonic variability. In the upper basin, Fe yielded 2,07%-3,91% and it was slightly higher from the A horizon towards the Bw-BC owed to the weak segregation of iron oxides. In the lower basin, the range found was between 3,33% and 4,99% with the highest accumulation in Bt-BC caused by clay + oxides illuviation. The vertical variability of Zn and Cr in terrace and alluvial plain soils was owed to the frequent flooding that controls the source minerals spatial distribution and to the consequent weathering resulting from redox potential changes. Microelement vertical variability in the valley slopes depends on a limited pedogenesis, thus intraprofile distribution is caused by removal and supply of aeolian materials.

Keywords : Micronutrients; Geoavailability; Morphogenesis and pedogenesis.

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