Clay Mineralogy of Basaltic Hillsides Soils in the Western State of Santa Catarina

Abstract

ABSTRACT:A commonly accepted concept holds that highly fertile, shallow soils are predominant in the Basaltic Hillsides of Santa Catarina State, in southern Brazil, but their agricultural use is restricted, either by excessive stoniness, low effective depth or steep slopes. Information about soil properties and distribution along the slopes in this region is, however, scarce, especially regarding genesis and clay fraction mineralogy. The objective of this study was to evaluate soil properties of 12 profiles distributed in three toposequences (T) of the Basaltic Hillsides in the State of Santa Catarina, two located in the valley of the Peixe River (Luzerna -T1 and Ipira -T2) and one in Descanso, in the far West of the state (T3). The main focus was the mineralogical composition of the clay fraction, identified by X-ray diffractometry (XRD), and its relations with the soil chemical properties. The morphological, chemical, and mineralogical properties of the soils of the toposequences differed from each other. In most soils, the position of the most intense XRD reflections indicated predominance of kaolinite (K) however, for being broad and asymmetric, a participation of interstratified kaolinite-smectite (K-S) was assumed. Soils of T2 and T3, located in regions with higher temperatures, lower water surplus, and lower altitude than those of T1, were more fertile, mostly redder, and contained higher proportions of smectites (S) and interstratified K-S mineral, accounting for a higher activity of the clay fraction of most soils. The T1 soils were generally less fertile, with lower clay activity and, aside from kaolinite, contained smectites with interlayered hydroxy-Al polymers (HIS). The low estimated smectite contents of the most fertile soils of all toposequences disagree with the high values of cation exchange capacity (CEC) and clay activity related to pure kaolinite soils. The broad and asymmetric reflections of most of the supposed kaolinites identified as dominant minerals indicate the presence of K-S interlayers, most likely contributing to raise the CEC of the soils.

Atributos químicos, físicos e mineralógicos de solos derivados de rochas sedimentares do Planalto de Lages-SC, Brasil

“…Os teores de COT foram mais elevados principalmente nos horizontes superficiais de todos os perfis, consequência do clima frio dominante na região, favorecendo o acúmulo de matéria orgânica (MO) (Tabela 1) (Ferreira, 2013;Almeida et al, 2018b).…”

Mineralogy and genesis of soils developed from ultrabasic and alkaline rocks of Lages Alkaline Complex, Brazil

“…with a value close to 1.25 nm, revealing that they are 2:1 layer clay minerals with hydroxy-Al polymers in the interlayers, probably vermiculites (VHE) (Barnhisel & Bertsch, 1989). Such minerals have been frequently found in the clay fraction of soils in the region of Lages (Almeida et al 2018;2019).…”

“…humid climate of the region, which favors its accumulation in the soil (Almeida et al, 2018;2019). The colors were dark brown and dark grayish brown on this horizon, while on the B horizon, brown and strong brown colors predominated.…”

Quaternary formations mapping in the region of Volta Grande do Rio Uruguai (Brazil)

“…Pistil and grail were used to obtain an air-dried fine soil -TFSA. Sodium hydroxide (NaOH) was used in the dispersion of the fine fraction at a concentration of 1.5 mol / L and in the proportionality of 25 ml to 20 g of TFSA, according to Almeida et al (2018). Afterward, the samples were taken directly to the shaker in which a mechanical dispersion of the solution took place at 155 cpm for 15 hours.…”