ABSTRACT Soils in the Depressão Central and Campanha Gaúcha in Rio Grande do Sul State, Brazil, developed from sedimentary rocks are mainly Alfisols (Luvissolos, Planossolos and Plintossolos) and Ultisols (Argissolos) with high textural contrast between A and/or E horizons and clayey B horizons. Red Ultisols dominate in well-drained areas in the summit. But many soils present redoximorphic features on the backslope and footslope, with mottled and/or nodules similar to plinthite due to the oscillating of the water table above the […]

ABSTRACT The simultaneous occurrence of high levels of exchangeable sodium percentage (ESP) and alkalinity in soils imposes restrictions on plant development and affects physical properties such as porosity, bulk density, permeability, and hydraulic conductivity. Although sodic soils are frequent in the flood plain of the São Lourenço River, northern Pantanal, Brazil, few studies focus on their formation and classification, especially with regard to specific processes and detailed classification into lower categorical levels by the different systems available. The aim of […]

In acid soils of a more tropical environment containing smectites, as well as in highly buffered subtropical soils containing Al hydroxide interlayered smectite (HIS) or vermiculite (HIV), the values of exchangeable Al, extracted by KCl solution (Al-KCl), may be exceptionally high, but not always toxic to the crops. This “exchangeable” Al does not come solely from electrostatic sites. This study aimed to evaluate the relationship between the Al extracted from the soil by KCl and ammonium oxalate solutions, and clay […]

Texture gradient is a prominent and ubiquitoud feature of Acrisol. The objective of this paper was to study the particle size distribution and mineralogy involved in the formation of the texture gradient of a subtropical soil in Rio Grande do Sul. Soil samples of a Red-Yellow Acrisol, formed on sedimentary parent material, were collected from trenches at two relief positions in an area of the Universidade Federal de Santa Maria, RS, Brazil. Soil samples were collected from profile 1, located […]

The formation of soils with argillic horizons was investigated to identify the pedological processes involved in the formation of lamellae and the abrupt textural gradient as well as their implication on the soil physical, chemical and mineralogical attributes. This study was carried out on a sandstone-derived soil toposequence, with profile (P1) occupying the higher part of the landscape (summit), profile (P2) on the backslope, and profile (P3) on the footslope. Soil chemical, mineralogical, micromorphological and particle size distribution analyses were […]