Getting the Dirt on Soils Capability Class and

Getting the Dirt on Soils: Capability Class and Slope Dr. David Lindbo Emeritus Professor, NC State University Director Soil Science Division, USDA-NRCS lindbo@ncsu. edu david. lindbo@usda. gov

Land Capability Classes

Capability Classes: Suited • Class I slight limitations • Class II moderate limitations: restrict plants or require moderate conservation practices • Class III severe limitations: restrict plants and/or require special conservation practices • Class IV soils have very severe limitations: restrict plants and/or require very careful management

Capability Classes: Unsuited • Class V little or no erosion but have limitations use restricted to pasture, rangeland, forestland, or wildlife habitat • Class VI severe limitations generally unsuitable for cultivation and use restricted to pasture, rangeland, forestland, or wildlife habitat • Class VII very severe limitations unsuitable for cultivation and restrict use to rangeland, forestland, or wildlife habitat

Capability Classes: Unsuited • Class VIII limitations that preclude commercial plant production and that restrict their use to recreational purposes, wildlife habitat, watershed, or esthetic purposes

Subclasses • • e – erosion risk w – water/wetness s – stony, droughty, shallow c – cold or very dry

Subclass Rankings e>w>s>c

Erosion - e • None, slight, moderate – no change • Severe – one class higher (2 e to 3 e) • Slope: – 0 -2% - 1 (5) – 2 -6%, 2 -8% - 2 e – 6 -10%, 8 -15%, 10 -15% - 3 e – 15 -25% - 4 e – 25 -45% - 6 e – 45+% - 7 e

Wetness - w Flooding • None-rare – class 1 • Occasional – class 2 w • Frequent – class 3 w

Wetness - w Drainage Class • • Well drained - 1 Moderately well drained - 2 w Somewhat poorly and clayey - 3 w Poorly drained - 4 w Very poorly drained and ponded - 6 w Tidal marsh - 7 w

Stony, droughty, shallow - s • • Very stony: 2 -15% slope - 4 s Very stony 15 -45% slope - 6 s Extremely stony: 2 -15% - 6 s Extremely stony: >15% - 7 s • Depth shallow - 1 -2 classes difference • Moderately deep (20 -40”) if hard bedrock 1 class difference

Percent Slope

What is the slope? % Slope = 45 o (Rise ÷ Run) x 100 1 ft 1/1 x 100 = 100% 90 o 45 o 1 ft

What is the slope? % Slope = (Rise ÷ Run) x 100 Rise 40 ft Run 100 ft % Slope = (40/100) x 100 = 40%

Measuring slope 10 ft 0. 5 ft (6 inches) % Slope = (0. 5 ft ÷ 10 ft) x 100 % Slope = 0. 05 x 100 This measurement must be in 10 ths of a foot % Slope = 5%

Clinometers

Questions?