TY - JOUR

T1 - Clay mineral composition drives soil structure behavior and the associated physical properties in Brazilian Oxisols

AU - Pessoa, Thaís Nascimento

AU - Bovi, Renata Cristina

AU - Nunes, Márcio Renato

AU - Cooper, Miguel

AU - Uteau, Daniel

AU - Peth, Stephan

AU - Libardi, Paulo Leonel

N1 - Publisher Copyright: © 2024 Elsevier B.V.

PY - 2024/9

Y1 - 2024/9

N2 - Soil aggregation controls several physical, chemical, and biological processes. Soil organic matter (SOM) and its stabilizing agents are regarded as the most important factors driving formation and stabilization of soil aggregates. However, aggregate stability in highly weathered soils may also be related to clay mineral composition and soil chemical properties. This study aims to evaluate the processes controlling soil aggregate stability and to understand the influence of soil chemical and clay mineral composition on the structural stability of highly weathered soils. Four Brazilian Oxisols were investigated: (P1) Xanthic Kandiustox, (P2) Rhodic Haplustox, (P3) Anionic Acrustox, and (P4) Typic Hapludox. Undisturbed and disturbed soil samples were collected from the Bw horizon under a native forest. Soil structural stability was evaluated using a variety of techniques and indices, including mean weight diameter (MWD) by hydraulic stress, mechanically-dispersible clay (MDC) by turbidimetry, tensile strength (TS) by crushing aggregates, and soil structural stability index (SSI) taking into account soil organic carbon (SOC). In general, P1 exhibited the highest MDC content (3.05 ± 0.54, Nephelometric Turbidity Unit, NTU/g L-−1), while P4 had the highest MWD (10.26 ± 0.24 mm) and the highest TS (80.42 ± 18.54 kPa) within the 8–4 mm aggregate size class. The TS for the 4–2 mm and 2–1 mm aggregate size classes was found to be equal for P2 and P4, with values ranging from 158.17 ± 24.70 kPa to 148.04 ± 38.50 kPa in the 4–2 mm class, and from 459.51 ± 189 kPa to 328.35 ± 78.22 kPa in the 2–1 mm one. The SSI was found to be inadequate for evaluating the structural stability of the Oxisols. In general, SOC was found to be the main stabilizing agent of larger aggregates, while clay mineral composition determined the stability of smaller aggregates. Goethite associated with gibbsite was more effective in increasing the structural stability of P2 and P4. Furthermore, kaolinites with low crystallinity, which are found in clayey Oxisols, resulted in a high specific surface area, particularly in Rhodic Haplustox and Typic Hapludox soils, which promoted more interactions with other clay minerals (e.g., goethite and gibbsite) and SOC, thereby increasing the tensile strength in these Oxisols. In fact, the formation and stabilization of aggregates in highly weathered soils depends on several factors, but the influence of clay mineral composition stands out as the most pronounced.

AB - Soil aggregation controls several physical, chemical, and biological processes. Soil organic matter (SOM) and its stabilizing agents are regarded as the most important factors driving formation and stabilization of soil aggregates. However, aggregate stability in highly weathered soils may also be related to clay mineral composition and soil chemical properties. This study aims to evaluate the processes controlling soil aggregate stability and to understand the influence of soil chemical and clay mineral composition on the structural stability of highly weathered soils. Four Brazilian Oxisols were investigated: (P1) Xanthic Kandiustox, (P2) Rhodic Haplustox, (P3) Anionic Acrustox, and (P4) Typic Hapludox. Undisturbed and disturbed soil samples were collected from the Bw horizon under a native forest. Soil structural stability was evaluated using a variety of techniques and indices, including mean weight diameter (MWD) by hydraulic stress, mechanically-dispersible clay (MDC) by turbidimetry, tensile strength (TS) by crushing aggregates, and soil structural stability index (SSI) taking into account soil organic carbon (SOC). In general, P1 exhibited the highest MDC content (3.05 ± 0.54, Nephelometric Turbidity Unit, NTU/g L-−1), while P4 had the highest MWD (10.26 ± 0.24 mm) and the highest TS (80.42 ± 18.54 kPa) within the 8–4 mm aggregate size class. The TS for the 4–2 mm and 2–1 mm aggregate size classes was found to be equal for P2 and P4, with values ranging from 158.17 ± 24.70 kPa to 148.04 ± 38.50 kPa in the 4–2 mm class, and from 459.51 ± 189 kPa to 328.35 ± 78.22 kPa in the 2–1 mm one. The SSI was found to be inadequate for evaluating the structural stability of the Oxisols. In general, SOC was found to be the main stabilizing agent of larger aggregates, while clay mineral composition determined the stability of smaller aggregates. Goethite associated with gibbsite was more effective in increasing the structural stability of P2 and P4. Furthermore, kaolinites with low crystallinity, which are found in clayey Oxisols, resulted in a high specific surface area, particularly in Rhodic Haplustox and Typic Hapludox soils, which promoted more interactions with other clay minerals (e.g., goethite and gibbsite) and SOC, thereby increasing the tensile strength in these Oxisols. In fact, the formation and stabilization of aggregates in highly weathered soils depends on several factors, but the influence of clay mineral composition stands out as the most pronounced.

KW - Iron and aluminum oxides

KW - Mean weight diameter

KW - Mechanically-dispersible clay

KW - Soil organic matter

KW - Tensile strength

UR - http://www.scopus.com/inward/record.url?scp=85198253733&partnerID=8YFLogxK

U2 - 10.1016/j.geodrs.2024.e00837

DO - 10.1016/j.geodrs.2024.e00837

M3 - Article

AN - SCOPUS:85198253733

VL - 38

JO - GEODERMA REGIONAL

JF - GEODERMA REGIONAL

SN - 2352-0094

M1 - e00837

ER -