Feições ferruginosas de solos do Vale do Araguaia, bioma Cerrado, Goiás, Brasil

Abstract

The landscape of the Araguaia Valley is composed of extensive plains and depressions flooded seasonally, where peculiar pedological features occur, associated with current or past weather. It was intended to study soils with ferruginous features in São Miguel do Araguaia, Goiás, to evaluate the pedogenesis, especially aspects related to origin and specificities of these features, and also potential of linear erosion, considering that land use and pedological characteristics have potentiated this process. Another hypothesis is that the progress of plinthization process can be evaluated from the distribution of soils in the toposequence and related processes of sediment deposition, assuming that the ferruginous features are contrasting and are changing along the landscape, and that the process of plintitization is modified when soil is submitted to drainage, since the dynamics of iron oxides is associated with oscillation of the groundwater slide. In order to test these hypotheses, eight soil profiles were selected, where seven trenches were opened the municipality of São Miguel do Araguaia and a trench in a floodplain of the municipality of Terezópolis de Goiás, Goiás. Deformed and undisturbed samples were collected from soil horizons for analysis. The most dissected areas of the municipality are associated to the lateritic cover, where F horizon occurs in several positions within the soil profile, influencing the magnitude of the water flow depending on the depth of occurrence, especially soil slope and soil cover, dictating erosive processes, and hence the degree of dissection of the relief. In general, the results of susceptibility analyzes and the potential for linear erosion demonstrate the low risk of erosive processes, even in the face of anthropogenic actions. The Plintossolos Pétricos presented a skeletal constitution and the ferruginous features are being degraded giving rise to an oxidic matrix. Based on the integrated analysis of pedological attributes, considering aspects related to the landscape, it was possible to establish a model that better explains the genesis of soils of Araguaia river plain, which is associated with erosion and relief inversion, and with consequent degradation of Fe nodules submitted to divergent conditions from those associated with their genesis. All profiles showed Fe and / or Mn remobilization, associated to nodule degradation, and sometimes segregating in more oxidized zones, with features usually associated with gray or brown matrix. The redoximorphic features are mainly the result of an endosaturation process, although there is evidence of pedogenic processes involving episaturation, such as the processes of ferrolysis and argiluviation, recurrent in some evaluated soil profiles.