Gneiss saprolite weathering and soil genesis along an east-west regolith sequence (NE Brazil)

Author(s)

Barros dos Santos, Jean Cheyson ^[1] ; Le Pera, Emilia ; de Souza Junior, Valdomiro Severino ^[3] ; Correa, Marcelo Metri ; de Azevedo, Antonio Carlos

Affiliation

^[1] Univ Fed Rural Pernambuco UFRPE, Dept Agron, BR-52171900 Recife, PE, Brazil. Le Pera, Emilia, Univ Calabria, Dipartimento Biol Ecol & Sci Terra, I-87036 Cosenza, Italy. Correa, Marcelo Metri, Univ Fed Rural Pernambuco UFRPE, Dept Ciencia Solo, Unidade Aca - Brazil

^[2] Univ Fed Rural Pernambuco UFRPE, Dept Agron, BR-52171900 Recife, PE, Brazil. Le Pera, Emilia, Univ Calabria, Dipartimento Biol Ecol & Sci Terra, I-87036 Cosenza, Italy. Correa, Marcelo Metri, Univ Fed Rural Pernambuco UFRPE, Dept Ciencia Solo, Unidade Acad Garanhuns, BR-55292270 Garanhuns, PE, Brazil. de Azevedo, Antonio Carlos, Univ Sao Paulo, ESALQ, Dept Ciencia Solo, BR-13418900 Piracicaba, SP - Brazil

• Document type: Journal article
• Source: CATENA; v. 150, p. 279-290, MAR 2017.
• Web of Science Citations: 8

Abstract

The pressure to increase biomass production worldwide has pushed the boundaries of agricultural lands towards fragile soils. This process is particularly intense in Pernambuco State, NE Brazil. Pernambuco features a moisture gradient, with soils developed from similar gneisses. Resistant structures within the rock influenced the internal movement and distribution of water, consequently influencing regolith genesis. This paper presents the mineralogical characteristics of three regolith profiles with shallow soils (here assumed to be soils in which the top of the Cr horizon is at a depth of 1.5 m or less) along a transect at 8 degrees S and discusses their weathering and pedogenetic processes. Samples were investigated via optical microscopy and scanning electron microscopy (SEM), Xray diffraction (XRD) and total chemical analysis by inductively coupled plasma - atomic emission spectrometry (ICP-AES). The presence of weathering-resistant quartz veins and planes in the rock structure played a central role in controlling the water dynamics and the advancement of the weathering front. Therefore, desilication was dominantly controlled by the pore network. Hence, the weathering indexes did not differ appreciably among the climatic zones, and both 1:1- and 2:1-type clays were found in all profiles, although the amount of clay minerals that formed and the degree of dissolution of the primary minerals varied among the climate types. From an agricultural perspective, the thinness of these soil profiles and the presence of leucocratic layers are the main drawbacks of the regoliths, whereas the capacity to supply plant nutrients via primary mineral dissolution near the root zone can be an advantage. (C) 2016 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 13/03703-2 - Soil-saprolite systems in southeast and northeast Brazil: morphological characteristics, geochemical-mineralogical evolution and environmental role
• Grantee: Antonio Carlos de Azevedo
• Support Opportunities: Regular Research Grants
• FAPESP's process: 12/12711-6 - ATTRIBUTES MORPHOLOGICAL, PHYSICAL, CHEMICAL AND MINERALOGICAL OF SHALLOW SOILS AND SAPROLITE IN THE SEMI-ARID REGION OF THE PERNAMBUCO STATE
• Grantee: Jean Cheyson Barros dos Santos
• Support Opportunities: Scholarships in Brazil - Doctorate