Caracterização de um perfil de planossolo nátrico na bacia hidrográfica do Rio Barra Nova - RN

Abstract

Regarding the characteristics related to the northeastern semi-arid region, this region stands out for having geo-environmental characteristics with a predominance of high temperatures combined with a precipitation pattern that favors the occurrence of a water deficit, both superficial and subsurface, that lasts a good part of the year, exerting direct influence on its ecological and soil dynamics. The formation of soils in these environments is influenced by low rainfall levels associated with high levels of evapotranspiration. Within this scenario, the class of Planossolos previously called Solonetz-Solodizados gains relevance, distinguishing itself by being one of the typical soils attributed to the lowest parts of this region. Planossolos have a very poor drainage capacity due to the formation and densification of their subsurface horizons resulting from the abrupt increase in clay. They are commonly found in areas subject to water saturation conditions, they present notable divergences between the A or E and B horizons, resulting in abrupt transitions. Therefore, this study aimed to characterize the morphological, physical and chemical nature of a Planossolo located in the the municipality of Ouro Branco, in addition to inferring the allochthonous or autochthonous character of its source material. Chemical analyzes (pH, exchangeable cations, exchangeable acidity, potential acidity, organic carbon, cation exchange capacity, among others), physical analyzes (particle size analysis) were carried out and its morphology was evaluated in the field. Granulometric analyzes highlighted the abrupt textural change between the horizons of the soil profile, revealing a densification in subsurface layers. Chemical analyzes revealed that the profile has a high pH, and with a predominance of Ca2+, Mg2+ and Na+ in the exchange complex, giving rise to a soil with high levels of sodium saturation. The textural contrast between the A, E and Btn horizons are consistent with characteristics resulting from the alteration of clay minerals “in situ” in the Btn horizon and the transport of materials between the horizons resulting from ferrolysis and argilluviation and/or elutriation. The results of sand fractionation revealed that the soil's original material is autochthonous, due to the homogeneity of the distribution of sand-sized particles vertically, ruling out the hypothesis of fluvial deposition considered from its position in the landscape.