Planosols Developed in Different Geoenvironmental Conditions in Northeastern Brazil

Abstract

ABSTRACT:The semiarid region of northeastern Brazil has a large area occupied by Planosols, where in the State of Pernambuco these soils are mainly used for livestock farming and subsistence crops. The knowledge on these soils is limited, which compromises the understanding on their behavior, potentialities and limitations.This study aimed to analyze morphological, chemical, physical and mineralogical attributes of Planosols developed under different geoenvironmental conditions. Morphological descriptions and chemical, physical and mineralogical analyses were performed in four profiles of Planosols along a rainfall gradient. An increase in rainfall allowed for an increase in the clay content in the Bt horizon and a reduction in ESP, EC, Na + , CEC, S, pH (water and KCl) and soil density. Horizons A and E were thicker in Planosols in more humid environments. The increase in ESP associated with the presence of expansive minerals (smectite and vermiculite) allowed the development of a prismatic structure in Haplic Planosols and a columnar structure in Natric Planosols. The mineralogical assembly is indicative of poorly weathered soils. The mineralogical assemblies of the silt and clay fractions were similar in the different geoenvironments, while higher contents of easily alterable minerals were observed in the composition of the sand fraction in environments with a drier climate.

Processos Pedogenéticos E Susceptibilidade Dos Solos À Degradação No Semiárido Brasileiro

“…Nos SXe o horizonte A geralmente é pouco espesso (< 10 cm), ocorrendo solos onde o horizonte A pode alcançar 15 cm, quando sob drenagem imperfeita, ou locais onde o horizonte A foi totalmente removido (BRASIL, 1971). Os Planossolos de áreas mais úmidas da região nordeste apresentam horizonte A e E mais espesso, enquanto os que ocorrem em áreas de clima semiárido não desenvolvem horizonte eluvial e o A apresenta espessura média de 15 cm (FERREIRA et al, 2016). Nos Planossolos truncados (remoção do horizonte A), os processos erosivos podem expor em superfície horizontes com elevados teores de sódio e de sais, pouco permeáveis e com considerável teor de argila dispersa em água.…”

Genesis and Classification of Sodic Soils in the Northern Pantanal

“…With the exception of the P3 profile, the other profiles had zero or very low H+Al values. For most of the horizons, the Ca 2+ values were lower than those of Mg 2+ , a situation observed in some sodic horizons of soils in the Northeast Region of Brazil (Oliveira et al, 2009;Ferreira et al, 2016b).…”

“…The presence of Al 3+ at high pH values, together with Ca 2+ values equal to zero, as observed in the 2Btgn2 horizon of the P5 profile, casts doubts on the differential thermodynamic equilibrium of this element in soils of the northern Pantanal. The Mg 2+ values, often higher than those of Ca 2+ , may be associated with alterations in clay minerals with Mg 2+ in their structure, such as smectite, as observed in the XRDs (Ferreira et al, 2016b). They may also have been controlled by the formation of calcite (CaCO 3 ) in a sodic alkaline pathway (Al-Droubi et al, 1980), which is feasible under the chemical composition of the waters of the São Lourenço River (Rezende Filho et al, 2012).…”

Ecotone Soils in Northeastern Brazil

“…Values of PREM above 20 mg L -1 indicate a low P adsorption capacity and it suggests a virtual absence of Fe oxides in these soils. Besides, seasonally alternating cycles of reduction and oxidation lead to clay destruction by ferrolysis and CEC reduction (BRINKMAN, 1970;FERREIRA et al, 2016). During the anaerobic phase, iron is reduced by microorganisms with the oxidation of organic matter and the formation of hydroxyl ions.…”