2D and 3D techniques to assess the structure and porosity of Oxisols and their correlations with other soil properties

Pessoa, Thaís Nascimento; Cooper, Miguel; Nunes, Márcio Renato; Uteau, Daniel; Peth, Stephan; Vaz, C. M. P.; Libardi, Paulo Leonel

doi:10.1016/j.catena.2021.105899

Cited by 13 publications

(8 citation statements)

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“…Similar areas with coalesced microaggregates associated with areas having a strong microgranular structure with highly to moderately separated microaggregates were earlier described by Gomes et al [2004] on thin sections of Bw horizons of clayey latosols located on the South American and Velhas geomorphic surfaces in the Cerrado Biome. They were again described very recently by Pessoa et al [2022] in latosols presenting different degrees of microgranular structure development as shown on the thin sections studied and the proportion of aggregates 8-16 mm in diameter measured in the Bw horizons.…”

Section: Development Of the Microgranular Structurementioning

confidence: 55%

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

Bruand¹,

Reatto²

2022

Comptes Rendus. Géoscience

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Polished sections of two Bw horizons collected in latosols located on the South American Surface (LSAS) and the Velhas Surface (LVS) in the Brazilian Central Plateau were studied using backscattered scanning images (BESI) in scanning electron microscopy and energy dispersive spectroscopy (EDS). BESI showed areas with a strong microgranular structure associated with areas having a weak to moderate microgranular structure. BESI at high magnification also showed the presence of

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Section: Development Of the Microgranular Structurementioning

confidence: 55%

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

Bruand¹,

Reatto²

2022

Comptes Rendus. Géoscience

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“…A recent study revealed that total pore space in Oxisols (Ferralsols counterpart in Soil Taxonomy) increases as the gibbsite/kaolinite ratio increases and the haematite/(haematite+goethite) ratio decreases (Pessoa et al, 2022). Pessoa et al (2022) showed that Rhodic Haplustox (Rhodic Ferralsols) have the highest total pore space among Oxisols equivalent to Xanthic, Geric, and Haplic Ferralsols. Therefore, if the clay mineralogy of Profundihumic Ferralsols were the reason for a greater porosity of PF compared to other Ferralsols, we should observe (i) a higher gibbsite/kaolinite ratio and a lower haematite/(haematite+goethite) than in Rhodic Ferralsols (Pessoa et al, 2022); and (ii) little variation in mineralogical composition among Profundihumic Ferralsols.…”

Section: Introductionmentioning

confidence: 99%

“…Pessoa et al (2022) showed that Rhodic Haplustox (Rhodic Ferralsols) have the highest total pore space among Oxisols equivalent to Xanthic, Geric, and Haplic Ferralsols. Therefore, if the clay mineralogy of Profundihumic Ferralsols were the reason for a greater porosity of PF compared to other Ferralsols, we should observe (i) a higher gibbsite/kaolinite ratio and a lower haematite/(haematite+goethite) than in Rhodic Ferralsols (Pessoa et al, 2022); and (ii) little variation in mineralogical composition among Profundihumic Ferralsols. However, the clay mineralogy of Profundihumic Ferralsols varies substantially according to the parent material (Marques et al, 2011; Schaefer et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

“…Geochemical transformation in Ferralsols occurs under intense and extended weathering that results in a clay mineral fraction dominated by low activity 1:1 phyllosilicates (kaolinite) and pedogenic Fe‐ and/or Al‐(hydr)oxides, for example, haematite, goethite, and gibbsite (Schaefer et al, 2008). A recent study revealed that total pore space in Oxisols (Ferralsols counterpart in Soil Taxonomy) increases as the gibbsite/kaolinite ratio increases and the haematite/(haematite+goethite) ratio decreases (Pessoa et al, 2022). Pessoa et al (2022) showed that Rhodic Haplustox (Rhodic Ferralsols) have the highest total pore space among Oxisols equivalent to Xanthic, Geric, and Haplic Ferralsols.…”

Section: Introductionmentioning

confidence: 99%

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Organic carbon enables the biotic engineering of beneficial soil structure in Profundihumic and Haplic Ferralsols

Martinez,

Lybrand,

McFarlane

et al. 2023

European J Soil Science

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We investigated how organic matter may, directly and indirectly, modify the porosity of Ferralsols, that is, deeply weathered soils of the tropics and subtropics. Although empirical and anecdotal evidence suggests that organic matter accumulation may increase porosity, a mechanistic understanding of the processes underlying this beneficial effect is lacking, especially so for Ferralsols. To achieve our end, we leveraged the fact that the Profundihumic qualifier of Ferralsols (PF) is distinguished from Haplic Ferralsols (HF) by both a much larger average carbon content in the first 1 m of soil depth (19 kg C m−3 in PF vs. 10 kg C m−3 in HF) and a significantly lower bulk density (1.05 ± 0.08 kg L−1 in PF vs. 1.21 ± 0.05 kg L−1 in HF). Through exhaustive modelling of carbon – bulk density relationships, we demonstrate that the lower bulk density of PF cannot be satisfactorily explained by a simple dilution effect. Rather, we found that bulk density correlated with carbon content when combined with carbon: nitrogen ratio (r2 = 0.51), black carbon content (r2 = 0.75), and Δ14C (r2 = 0.81). Total pore space was greater in PF (61 ± 3%) than in HF (55 ± 2%), but x‐ray computed tomography revealed that pore space inside soil aggregates of 4–5 mm diameter does not vary between the studied Ferralsols. We further observed nearly twice as many roots and burrows in PF compared with HF. We thus infer that the mechanism responsible for the increase in porosity is most likely an enhancement of resource availability (e.g., energy, carbon, and nutrients) for the organisms (earthworms, ants, termites, etc.) that physically displace soil particles and promote soil aggregation. As a result of increased resource availability, soil organisms can create especially the mesoscale structural soil features necessary for unrestricted water flow and rapid gas exchange. This insight paves the way for the development of land management technologies to optimize the physical shape and capacity of the soil bioreactor.

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“…Due to their high stability, the structural unity is preserved even after events of great fluxes of energy and mass, like heavy rainfall: These so‐called pseudosands have already been described several decades ago (Bui et al., 1989; Neufeldt et al., 1999; Santos et al., 1989; Sharma & Uehara, 1968). Nowadays, pseudosands are often referred to by many other non‐explicit names like “(clay) micro‐/macroaggregates,” “granular (micro‐/macro‐)structure,” “(micro/macro) nodular structures,” “pseudo‐particles,” and others (e.g., Cooper et al., 2005; Neufeldt et al., 1999; Pessoa et al., 2022; Rabbi et al., 2015; Radulovich et al., 1992; Volland‐Tuduri et al., 2005). Confusion is predictable when no unique name and no clear definition are provided, as it is the case for the term “aggregate” (Baveye, 2021; Letey, 1991; Totsche et al., 2018; Vogel et al., 2022).…”

Section: Introductionmentioning

confidence: 99%

The “extra pinch” of pseudosand to enhance tropical biogeochemical processes understanding

Kilian Salas,

Meurer,

Boy

et al. 2024

J. Plant Nutr. Soil Sci.

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Despite knowing better, water‐stable aggregates like pseudosands are still disintegrated into their clay‐ and silt‐sized bits and pieces to serve standardization in texture determination. Lacking yet a viable alternative, this deliberately committed mistake seems the contemporary best practice for modeling purposes, which is far from being ideal. Here, we propose this misconception to be a major cause for flawed process understanding of tropical soils, leading to substantial uncertainties in model development. There is enough evidence as to why pseudosands are neither sand nor the plain sum of their clay‐ and silt‐sized units and should therefore better be defined as an additional soil texture class for which properties have yet to be examined across the tropics.

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2D and 3D techniques to assess the structure and porosity of Oxisols and their correlations with other soil properties

Cited by 13 publications

References 50 publications

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

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

Organic carbon enables the biotic engineering of beneficial soil structure in Profundihumic and Haplic Ferralsols

The “extra pinch” of pseudosand to enhance tropical biogeochemical processes understanding

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