Which evidence attests for soil aggregate rupture? A new criterion to determine aggregate tensile strength

Barbosa, Luis Alfredo Pires; Ferraz, Antônio Carlos de Oliveira

doi:10.1016/j.still.2019.104530

Cited by 10 publications

(4 citation statements)

References 30 publications

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“…Moreover, there might be criteria other than the work needed for a certain level of strain that are better indicators of mechanical strength. Notably, the frequent notion of “aggregate failure,” for example, defined by the emergence of equatorial cracks as suggested by Barbosa and de Oliveira Ferraz (2020) is not suitable for microaggregates because these distinct equatorial cracks do not seem to occur at this scale. Furthermore, the shape of microaggregates can strongly deviate from a sphere, which violates a basic assumption of the concept of tensile strength measured by the force at aggregate rupture (Rogowski et al., 1968).…”

Section: Discussionmentioning

confidence: 99%

Exploring the mechanisms of diverging mechanical and water stability in macro‐ and microaggregates

Roosch,

Felde,

Uteau

et al. 2023

J. Plant Nutr. Soil Sci.

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BackgroundSoil stability is often evaluated using either mechanical or hydraulic stress. The few studies that use both approaches suggest that these two types of stability behave differently.AimsOur aim was to explore the mechanisms of aggregate stability regarding mechanical and water stability at the macro‐ and microscale, among other things, the effect of differing pore structure and soil organic matter content.MethodsSamples were taken from two adjacent plots that were expected to differ in stability due to land use, that is, cropped versus bare fallow (BF). The stability of dry‐separated macroaggregates (8–16 mm) and microaggregates (53–250 μm) was determined via wet sieving and unconfined uniaxial compression tests. To explore the mechanisms of stability, 3D pore characteristics were analyzed with microtomography scans. Furthermore, the contents of carbon and exchangeable polyvalent cations as well as contact angles were determined.ResultsWater stability of macroaggregates was much higher in the cropped plot (geometric mean diameter 0.65–2.37 mm [cropped] vs. 0.31–0.56 mm [BF]), while mechanical stability was very similar (median work 17.3 [cropped] and 17.5 N mm [BF]). The two size fractions behaved similarly regarding both types of stability, with more pronounced differences in macroaggregates. Several soil characteristics, like carbon, exchangeable calcium, and higher connectivity of pores to the aggregate exterior, contributed to water stability. Regarding mechanical stability, the destabilizing effect of lower carbon content and exchangeable calcium in the BF plot was counterbalanced by a lower porosity.ConclusionsMechanical and water stability behaved differently in the two plots due to the different deformation mechanisms.

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Section: Discussionmentioning

confidence: 99%

Exploring the mechanisms of diverging mechanical and water stability in macro‐ and microaggregates

Roosch,

Felde,

Uteau

et al. 2023

J. Plant Nutr. Soil Sci.

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“…This test consists basically of a controlled aggregate rupture while the forces are monitored. The point of failure for each aggregate was detected when a sudden drop in force 56 . The rupture force, , was used to calculate the tensile strength, 54 : where is the diameter of an individual aggregate, calculated as 57 .…”

Section: Methodsmentioning

confidence: 99%

“…The trained algorithm was used to predict new data combining variables and output. For the assessment of the regression algorithm 56 the metrics were: 1) coefficient of determination R2-score, which represents the proportion of the variance in the dependent variable that can be explained by the independent variables in the mode (the best possible score is 1.0) and 2) Mean Absolute Error in percentage (MAEp), which finds all absolute errors (xi–x), adds them all and divide by the number of errors. In RF, the depth of a variable used as a decision node in a tree can be used to assess the relative importance of that variable in predicting the output.…”

Section: Methodsmentioning

confidence: 99%

Synergistic effects of organic carbon and silica in preserving structural stability of drying soils

Barbosa,

Stein,

Gerke

et al. 2024

Sci Rep

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Predicted climate warming and prolonged droughts pose a threat to the soil structure as organic carbon losses weaken the stability of soil aggregates. Well-structured soils are important for storage and movement of water, solutes, and air, the development of plant roots, as habitat for soil organisms, and the microbial activity. Structural stability is measured in terms of hydro-mechanical properties. This study compares effects of amorphous silica with those of organic carbon on stability parameters during drying of aggregates from relatively finer- and coarser-textured soils. Silica amendment enhanced the positive effect of organic carbon on structural stability in terms of the tensile strength. Synergistic effects between silica and organic carbon in soil colloids appear to dynamically alter aggregate density and friability (i.e., ability to crumble) during drying. Silica together with organic carbon could help soil management to reduce negative effects of predicted prolonged droughts on soil structure and stability.

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“…TS is determined by a simple test, in a wide range of aggregate sizes, which improves its statistical confidence. According to TS values, the soil quality is reached when aggregates are small enough to allow of the formation of a friable seeding layer after soil preparation, but large enough to support the weight of heavy equipment with a minimum compaction (Lehrsch et al, 2012;Barbosa & Ferraz, 2020). The surface layer of an Argissolo Vermelho-Amarelo (Typic Hapludult) under annual crops showed TS values lower than those observed under natural pasture or natural vegetation, according to Reis et al (2014b).…”

Section: Introductionmentioning

confidence: 99%

Physical quality of soil under secondary forest, leguminous trees, and degraded pasture

Faustino

Marciano

Andrade

2021

Pesq. agropec. bras.

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The objective of this work was to assess the efficiency of revegetation with forest leguminous species, for the recovery of the physical quality of a Typic Hapludult under degraded pasture, located in a steep-slope tropical landscape in Southeastern Brazil. Soil samples were collected at the 0-0.10 m and 0.10-0.20 m depths, in areas under Acacia auriculiformis (northern black wattle), Mimosa caesalpiniifolia (“sabiá”), Inga edulis (“ingá”), secondary forest (“capoeira”), and degraded pasture. Tensile strength (TS) was evaluated in soil aggregates of the size classes 8.0-12.5 mm and 12.5-19.0 mm, for the variables TS 8 and TS 12.5, respectively. The lowest mean values of both variables always occurred under the pasture cover (TS 8 of 37.1 kPa and TS 12.5 of 22.7 kPa, for the 0-0.10 m soil layer; and TS 8 of 39.2 kPa and TS 12.5 of 22.8 kPa, for the 0.10-0.20 m soil layer). The highest TS mean values were obtained under the “capoeira” cover (TS 8 of 62.2 kPa, for the 0-0.10 m soil layer) and “sabiá” cover (TS 12.5 of 46.0 kPa, for the 0-0.10 m soil layer; and TS 8 of 53.0 kPa and TS 12.5 of 51.4 kPa, for the 0.10-0.20 m soil layer). Land revegetation with leguminous trees recovers the soil physical quality, since the TS values under the evaluated covers are predominantly closer to those of the secondary forest than to those of the degraded pasture.

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Which evidence attests for soil aggregate rupture? A new criterion to determine aggregate tensile strength

Cited by 10 publications

References 30 publications

Exploring the mechanisms of diverging mechanical and water stability in macro‐ and microaggregates

Exploring the mechanisms of diverging mechanical and water stability in macro‐ and microaggregates

Synergistic effects of organic carbon and silica in preserving structural stability of drying soils

Physical quality of soil under secondary forest, leguminous trees, and degraded pasture

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