Epi and endosaturation affecting redoximorphic features and pedogenesis in subtropical soils with high textural contrast developed from sedimentary rocks

Almeida, Jaime Antônio de; Santos, Pablo Grahl dos

doi:10.36783/18069657rbcs20210044

Cited by 1 publication

(7 citation statements)

References 16 publications

(24 reference statements)

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“…The occurrence of petroplinthite was not observed in the evaluated profiles, as suggested by Almeida and Santos (2021) to support the presence of plinthites. This fact provides further evidence that the reddish features present in these soils are not plinthic materials or are in an incipient process to be identified as plinthites.…”

Section: Discussionmentioning

confidence: 69%

“…The Fe OAA /Fe DCB ratios were extremely low, evidencing the predominance of crystalline forms of Fe. As expected, the Fe contents in mottles are higher than those in matrix (Daniels et al,1978;Anjos et al, 1995;Miguel et al, 2013;Almeida and Santos, 2021). Nevertheless, according to Almeida and Santos (2021), when the Fe data were related to the morphological test of the soil wetting and drying cycles, the authors found that the increases in Fe contents in the mottles were not sufficient to confirm its plinthic nature.…”

Section: Discussionmentioning

confidence: 80%

“…In the highland sedimentary environment of the Central Depression of Rio Grande do Sul State (RS), southern Brazil, soils with low permeability in the B horizon, called Argissolos (Acrisols, Alisols, Luvisols) and Plintossolos (Plinthosols), are very common, especially in the lower portion of the landscape, mainly due to the high textural contrast and the fluctuation of the water table level (Pedron et al, 2012;Almeida and Santos, 2021). The low permeability favors the formation of shallow (up to 1.00 m) and imperfectly drained profiles (solum), with the occurrence of redoximorphic features from the top of the Bt horizon to the Cr, providing adequate conditions for the formation of plinthites and petroplinthites (Pedron and Dalmolin, 2019).…”

Section: Introductionmentioning

confidence: 99%

“…The periodic excess of moisture in the subsurface soil horizons promotes the formation of depletion zones, where the reduction of iron oxides occurs, its mobilization out of the profile or concentration in zones with higher O 2 concentration (Eze et al, 2014). This process, mainly associated with desilication, eluviation/iluviation, ferrolysis and plinthization, results in mottles that are sometimes difficult to be appropriately identified in the field, generating confusion, especially between plinthites and saprolite residues (Almeida and Santos, 2021).…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, some studies have been dedicated to the theme, trying to qualify the understanding of plinthites in Brazilian soils. Jacomine et al (2010) carried out tests to confirm the presence of plinthites in soil samples, based on wetting and drying cycles of the samples and their resistance to crumbling and hardening, also used by Almeida and Santos (2021). The stability of plinthites after different drying methods was evaluated by Martins et al (2018).…”

Section: Introductionmentioning

confidence: 99%

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Identification of plinthite or saprolite residue in soils with high textural contrast in the southern Brazil

Pereira¹,

Pedron²,

Dalmolin³

et al. 2022

Revista Brasileira De Ciência Do Solo

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Soils classified as Alisols are very frequent in the sedimentary agricultural areas of southern Brazil. The presence of red mottles with morphology similar to plinthite and saprolite residue is very common in these soils, and its identification can be considered a difficult task, both in the field and in the laboratory. The incorrect identification of these redoximorphic features can affect soils' taxonomic and technical classification. We aimed to compare morphological, physical, chemical and mineralogical data to identify reddish mottles, possibly plinthites or saprolite residues, that occur in soils with high textural contrast in southern Brazil. Four soil profiles classified as Argissolos Bruno-Acinzentados (Alisols) were sampled. Matrix and mottles samples from the horizon Bt, CB, C and Cr were separated and subjected to morphological, granulometric, total sand fractionation, chemical extractions of iron and potassium and mineralogical features. Peds from each horizon were submitted to the submersion test in water for 2 and 8 hours and to 5 wetting and drying cycles. The mineralogy indicated the low degree of alteration of the samples, with abundant presence of 2:1 minerals and feldspars, even in the clay fraction. The saprolite resisted in the water submersion tests, making it difficult to interpret the results for the correct identification between plinthites and saprolite fragments. The morphological field data associated with the results of the tests of submersion in water, the cycle of wetting and drying, the dissolution of K and mineralogy, indicate the saprolithic nature of the mottles in all horizons and profiles. The submersion test in water for 2 and 8 hours was not efficient for the plinthite/saprolite identification. The cycle of wetting and drying tests allowed the identification of saprolite.

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Section: Discussionmentioning

confidence: 69%