Mineralogical, chemical and electrochemical attributes of soils

Abstract

A set of attributes endows the soils with distinctive characteristics and astute understanding is required in order to formulate suitable strategies for soil management. The aim of this study was to physically, chemically and mineralogically characterize samples of the main soil classes in Minas Gerais, Brazil, determine the point of zero salt effect (PZSE) and the point of zero charge (PZC), and ascertain the correlation between these factors and soil attributes. The soils evaluated presented different textural classes ranging from loamy sand (Entisol) to very clayey (some Oxisols and Ultisols). The soils differed substantially in terms of fertility, presenting a range from dystrophic (low fertility, base saturation < 50 %) to eutrophic character (fertility, base saturation ≥ 50 %), even within the same soil class, such as the Oxisols, which suggests the concurrence of the parent material. Highly weathered soils are predominant in Minas Gerais and these soils are composed predominantly of kaolinite, gibbsite, goethite and hematite. Traces of hydroxy-Al interlayered vermiculite and illite were also found in the Oxisols, Ultisols and Inceptisols. A correlation between the PZSE and the PZC in the A horizon was observed. A high degree of correlation was observed between the PZC and the exchangeable aluminum and the ratio of iron obtained by ammonium oxalate and dithionite-citrate (Fe o /Fe d) in both the A and B horizons of soil classes. The results obtained reinforce the importance of knowledge of soil attributes to the adoption of practices such as the management of phosphate fertilization in clayey soils and liming in soils rich in aluminum.

Morphology, chemical composition and origin of 2:1 phyllosilicates in Bw horizons of latosols of the Brazilian Central Plateau: contribution to the discussion of the microgranular structure origin

“…They found HIVs in the clay fraction of six of them. Traces of HIVs were again found very recently, associated to traces of illite, by Almeida et al [2021] in latosols located in the Minas Gerais state. Marques et al [2011] studied the mineralogy of the clay fraction of latosols developed on a large range of parent materials using XRD and HIVs were only found in the clay fraction of latosols developed on basalts but their origin was not discussed.…”

Allochthonous material originating from saprolite as a marker of termite activity in Ferralsols

“…Lastly, fine sand-size particles (50-500 µm long) were numerous in F1 and poorly present in F3 (Table 1). Thus, even if the elongated particles showing an internal structure of phyllosilicates varied in size, in abundance in the groundmass fabric of the submillimetric granular aggregates and in K 2 O content, they were present in the four ferralic B horizons studied and corresponded to the 2:1 clay minerals identified earlier using XR diffraction but without having the possibility to describe their morphology and to determine their chemical composition 29,[31][32][33][34][35][36][37] .…”

“…2a). Globally, the increase in the Al 2 O 3 content when the K 2 O decreased has to be considered as the result of the intercalation of hydroxy-Al in the inter-layer space during the weathering process of the muscovite particles 18 leading to the formation of hydroxy-Al interlayered vermiculites (HIV) as shown by several authors 29,[31][32][33][34][35][36][37] .…”