Ciencia del Suelo (Jul 2010)
Hidromorfía y condiciones ácuicas en suelos de la llanura aluvial de Tucumán (Argentina) Hydromorphy and aquic conditions in soils of the alluvial plain of Tucumán (Argentina)
Abstract
Se seleccionaron cuatro perfiles de suelo con distinta clase de drenaje con el objetivo de analizar la intensidad del proceso de hidromorfía, y considerar cuáles cumplen con las condiciones ácuicas. Estos fueron: La Aguadita (Udipsamment típico, térmico, bien drenado), La Fronterita XI (Hapludol típico, franco grueso, illítico, térmico, moderadamente bien drenado), La Fronterita X (Argiudol ácuico, franco fino, illítico, térmico, imperfectamente drenado) y Famaillá (Argiu-dol ácuico, fino, illítico, térmico, imperfectamente drenado). Los suelos muestran condiciones de endosaturación durante seis meses al año, con un ascenso del nivel freático durante verano-otoño y un descenso en invierno-primavera. La intensidad de la reducción se evaluó en base a la distribución de hierro y manganeso secundarios asociados a los rasgos redoximórficos identificados micromorfológicamente. En los perfiles bien drenados y moderadamente bien drenados, los Fe d y Mn d mostraron escasa movilidad con valores entre 0,50-0,80% y 0,03-0,06%, respectivamente, y rasgos redoximórficos de escaso desarrollo con un índice Mn/Fe d The profiles of four soils with different drainage types were selected in the alluvial plain of Tucumán in order to analyze the intensity of the hydromorphy and detect which of the soils conforms to an aquic conditions. The four types were: La Aguadita (thermic Typic Udipsamment) (well-drained), La Fronterita XI (coarse loamy, illitic, thermic Typic Hapludoll) (moderately well-drained), La Fronterita X (fine loamy, illitic, thermic Aquic Argiudoll) (imperfectly drained), and Famaillá (fine, illitic, thermic Aquic Argiudoll) (imperfectly drained). The soils show endosaturation conditions for six months of the year, with an increase in water level during summer-autumn and a decrease in winter-spring. The degree of reduction was assessed in terms of the distribution of iron and manganese associated with redoximorphic features analyzed on a micromorphological scale. In the well-drained and moderately well-drained profiles, Fe d and Mn d show little mobility, with the respective values ranging from 0.50-0.80% and 0.03-0.06%, Mn d / Fe d <0.08% and underdeveloped redoximorphic features. In the profiles with imperfect drainage, the Fe d sometimes co-migrates with and sometimes separates from clay, with the segregation of Fe d outside the profile. Mn d has low values (0.01-0.06%) with an increase of 0.20% in the BC of La Fronterita X, Mn/Fe d = 0.33 and more developed redox features. The analysis suggests that the hydromorphic process increases from the moderately well-drained La Fronterita XI profile towards the imperfectly drained La Fronterita X and Famaillá profiles. The former two profiles are expressed in the Mn/Fe d ratio and in the increasing size and abundance of redox features as observed on a micromorphological scale; and the Famaillá profile in the low mean value of Fe d and Mn, and the presence of redoximorphic features. The Fronterita X and Famaillá profiles present the most reduced conditions among the studied soils and are assumed to conform to an aquic regime.
