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Umbric epipedon (USDA Soil Taxonomy, 13th edition)

Source: R/diagnostics-epipedons-usda.R
umbric_epipedon_usda.Rd

A thick, dark-colored, base-poor (BS < 50 percent) mineral surface horizon. Differs from mollic in low base saturation; qualifies the Humults / Humic / Umbric subgroups in many orders.

Usage

umbric_epipedon_usda(pedon, max_bs = 50, min_oc_pct = 0.6)

Arguments

pedon

A PedonRecord.

max_bs

Maximum BS (default 50 – "less than 50 percent").

min_oc_pct

Minimum OC (default 0.6).

Value

A DiagnosticResult.

Details

KST 13ed required characteristics (Ch. 3, pp 18-20):

  • Color: same as mollic (V<=3 moist, V<=5 dry, chroma<=3);

  • Base saturation (NH4OAc) < 50 percent in some part;

  • Organic carbon >= 0.6 percent (or 0.6 absolute > C);

  • Thickness: same rules as mollic (18 / 25 / 10 cm);

  • Structure: peds <= 30 cm OR rupture-resistance <= moderately hard.

References

Soil Survey Staff (2022), KST 13ed, Ch. 3, pp 18-20.