Plinthite nodule interior
Plinthite nodules are checked for degree of cementation to determine plinthite versus ironstone. To test for cementation, the specimen is air dried and then submerged in water for at least 1 hour. Cemented materials will resist slaking. Cementation class placements do not pertain to the soil material at the field water state.
Plinthite nodules are less than strongly cemented. Most plinthite nodules are weakly or moderately cemented.
Weakly cemented nodules fail under strong force applied slowly between thumb and forefinger.
Moderately cemented nodules cannot be failed between thumb and forefinger but can be between both hands or by placing on a nonresilient surface and applying gentle force underfoot.
Note: Wording indicates plinthite maybe cemented, but cementation is not required. Whereas, if cementation was required, the wording would be "moderately cemented or less cemented".
Ironstone concretions are strongly or more cemented. Strongly cemented materials cannot be failed in hands but can be underfoot by full body weight.
Plinthite normally forms in a horizon below the surface, but it may form at the surface in a seepy area at the base of a slope. From a genetic viewpoint, plinthite forms by the segregation, transport, and concentration of iron. In many places iron may have been transported vertically or horizontally from other horizons or from higher adjacent soils. Plinthite may occur as a constituent of a number of horizons, such as an epipedon, a cambic horizon, an argillic horizon, a kandic horizon, an oxic horizon, or a C horizon. Generally, plinthite forms in a horizon that is (or has been) periodically saturated with water. Initially, the segregated iron forms more or less clayey, reddish, or brownish redox concentrations.
Individual plinthite nodules commonly have 3 to more than 10 percent citrate-dithionite extractable Fe.
For more information about describing and sampling soils, visit:
www.nrcs.usda.gov/resources/guides-and-instructions/field...
or Chapter 3 of the Soil Survey manual:
www.nrcs.usda.gov/sites/default/files/2022-09/The-Soil-Su...
For additional information on "How to Use the Field Book for Describing and Sampling Soils" (video reference), visit:
www.youtube.com/watch?v=e_hQaXV7MpM
For additional information about soil classification using USDA-NRCS Soil Taxonomy, visit:
www.nrcs.usda.gov/resources/guides-and-instructions/keys-...
or;
www.nrcs.usda.gov/resources/guides-and-instructions/soil-...
Plinthite nodule interior
Plinthite nodules are checked for degree of cementation to determine plinthite versus ironstone. To test for cementation, the specimen is air dried and then submerged in water for at least 1 hour. Cemented materials will resist slaking. Cementation class placements do not pertain to the soil material at the field water state.
Plinthite nodules are less than strongly cemented. Most plinthite nodules are weakly or moderately cemented.
Weakly cemented nodules fail under strong force applied slowly between thumb and forefinger.
Moderately cemented nodules cannot be failed between thumb and forefinger but can be between both hands or by placing on a nonresilient surface and applying gentle force underfoot.
Note: Wording indicates plinthite maybe cemented, but cementation is not required. Whereas, if cementation was required, the wording would be "moderately cemented or less cemented".
Ironstone concretions are strongly or more cemented. Strongly cemented materials cannot be failed in hands but can be underfoot by full body weight.
Plinthite normally forms in a horizon below the surface, but it may form at the surface in a seepy area at the base of a slope. From a genetic viewpoint, plinthite forms by the segregation, transport, and concentration of iron. In many places iron may have been transported vertically or horizontally from other horizons or from higher adjacent soils. Plinthite may occur as a constituent of a number of horizons, such as an epipedon, a cambic horizon, an argillic horizon, a kandic horizon, an oxic horizon, or a C horizon. Generally, plinthite forms in a horizon that is (or has been) periodically saturated with water. Initially, the segregated iron forms more or less clayey, reddish, or brownish redox concentrations.
Individual plinthite nodules commonly have 3 to more than 10 percent citrate-dithionite extractable Fe.
For more information about describing and sampling soils, visit:
www.nrcs.usda.gov/resources/guides-and-instructions/field...
or Chapter 3 of the Soil Survey manual:
www.nrcs.usda.gov/sites/default/files/2022-09/The-Soil-Su...
For additional information on "How to Use the Field Book for Describing and Sampling Soils" (video reference), visit:
www.youtube.com/watch?v=e_hQaXV7MpM
For additional information about soil classification using USDA-NRCS Soil Taxonomy, visit:
www.nrcs.usda.gov/resources/guides-and-instructions/keys-...
or;
www.nrcs.usda.gov/resources/guides-and-instructions/soil-...