Disaggregation of Cataula Soil
Slaking v. Disaggregation in soils with Fragic Soil Properties
a distinction without a difference???
As you view the video, note how the soil fragments on the top react to rapid wetting. They are blocky peds from the Btx horizon of a Cataula soil (fine, kaolinitic, thermic Oxyaquic Kanhapludult). The fragments on the bottom are platy peds from the same horizon. Samples were taken at a depth of about 50 to 100cm.
These soils align with the concept of a dual subgroup classification (Oxyaquic Fragic) if offered as an option in Soil Taxonomy. As currently written in the KEYS, the Oxyaquic subgroup takes higher priority than the Fragic subgroup. Cataula soils are mapped in association with Cecil soils. They commonly occur along shoulder slopes and toeslopes next to areas designated as Cecil.
They are very similar to Cecil soils but exhibit fragic soil properties in the subsoil (Btx horizons) ranging from 20 to 60 percent resulting in a transitory perched water table from 2 to 4 feet in winter and spring. The fragic soil properties are noticeable—dense, compact, brittle and root-restrictive. Excavation difficulty is high to very high even when moist. Matrix color indicates a very coarse, slightly reticulate mottle pattern. Cracks or zones that roots can enter are mostly less than 10 cm apart; therefore, failing the fragipan concept even though many pedons have more than 60 percent fragic soil properties.
In March 1982 the series was revised to change the classification from Typic Fragiudults to Typic Hapludults. The November 1998 OSD revision changed the classification to Oxyaquic Kanhapludults.
Distinguishing Slaking from Disaggregation
Disaggregation is the general process by which soil aggregates break down when submerged in water. Within this process, two distinct behaviors can be observed: slaking and sloughing.
Slaking is a rapid, dynamic form of disaggregation, most often associated with fragic soil properties—horizons that are compact: dense, brittle, and root-restrictive. When air-dried aggregates from these soils are submerged, water infiltrates internal pores, creating pressure that causes the aggregates to “pop” as they fragment. A 50–75 mm ped may collapse completely within 5–10 minutes, reflecting the restrictive porosity and rigidity of soils that exhibit fragic soil properties.
Sloughing, by contrast, is a slow, uniform breakdown. Aggregates gradually soften and weaken as water infiltrates and cohesive forces diminish. Collapse occurs over several minutes to hours, without the sudden fragmentation typical of slaking.
Distinguishing between slaking and sloughing is more than a matter of terminology—it provides a practical diagnostic tool for recognizing fragic soil properties and identifying fragipans, aiding soil classification and correlation.
Disaggregation of Cataula Soil
Slaking v. Disaggregation in soils with Fragic Soil Properties
a distinction without a difference???
As you view the video, note how the soil fragments on the top react to rapid wetting. They are blocky peds from the Btx horizon of a Cataula soil (fine, kaolinitic, thermic Oxyaquic Kanhapludult). The fragments on the bottom are platy peds from the same horizon. Samples were taken at a depth of about 50 to 100cm.
These soils align with the concept of a dual subgroup classification (Oxyaquic Fragic) if offered as an option in Soil Taxonomy. As currently written in the KEYS, the Oxyaquic subgroup takes higher priority than the Fragic subgroup. Cataula soils are mapped in association with Cecil soils. They commonly occur along shoulder slopes and toeslopes next to areas designated as Cecil.
They are very similar to Cecil soils but exhibit fragic soil properties in the subsoil (Btx horizons) ranging from 20 to 60 percent resulting in a transitory perched water table from 2 to 4 feet in winter and spring. The fragic soil properties are noticeable—dense, compact, brittle and root-restrictive. Excavation difficulty is high to very high even when moist. Matrix color indicates a very coarse, slightly reticulate mottle pattern. Cracks or zones that roots can enter are mostly less than 10 cm apart; therefore, failing the fragipan concept even though many pedons have more than 60 percent fragic soil properties.
In March 1982 the series was revised to change the classification from Typic Fragiudults to Typic Hapludults. The November 1998 OSD revision changed the classification to Oxyaquic Kanhapludults.
Distinguishing Slaking from Disaggregation
Disaggregation is the general process by which soil aggregates break down when submerged in water. Within this process, two distinct behaviors can be observed: slaking and sloughing.
Slaking is a rapid, dynamic form of disaggregation, most often associated with fragic soil properties—horizons that are compact: dense, brittle, and root-restrictive. When air-dried aggregates from these soils are submerged, water infiltrates internal pores, creating pressure that causes the aggregates to “pop” as they fragment. A 50–75 mm ped may collapse completely within 5–10 minutes, reflecting the restrictive porosity and rigidity of soils that exhibit fragic soil properties.
Sloughing, by contrast, is a slow, uniform breakdown. Aggregates gradually soften and weaken as water infiltrates and cohesive forces diminish. Collapse occurs over several minutes to hours, without the sudden fragmentation typical of slaking.
Distinguishing between slaking and sloughing is more than a matter of terminology—it provides a practical diagnostic tool for recognizing fragic soil properties and identifying fragipans, aiding soil classification and correlation.