Soil Science & Analysis Flashcards

Which soil color matrix notation using the Munsell system indicates the strongest evidence of prolonged saturation?

Answer: 5Y 4/1

5Y 4/1 has a hue of 5Y and chroma of 1, indicating a gleyed, low-chroma color typical of prolonged anaerobic saturation.

In the Corps of Engineers Wetland Delineation Manual, what is the minimum percentage of a soil matrix that must display redoximorphic features to meet the hydric soil criterion under problematic hydric soil indicators?

Answer: 2%

Some problematic hydric soil indicators, such as F21 (Red Parent Material), require redox concentrations in at least 2% of the matrix.

Which process is primarily responsible for the formation of mottles and redox concentrations in hydric soils?

Answer: Reduction and translocation of iron and manganese

Alternating reduction and oxidation cycles mobilize iron and manganese, which precipitate as redox concentrations when re-oxidized.

A soil pit reveals a dark gray (N 4/) matrix with no other features in the upper 12 inches. Which hydric soil indicator does this BEST match?

Answer: A4 - Sandy Gleyed Matrix

Indicator A4 (Sandy Gleyed Matrix) applies to sandy soils with a gleyed matrix (N or 10Y/5GY hues) in the upper 15 cm.

When measuring soil organic matter content for hydric soil classification, which laboratory method is considered the standard reference?

Answer: Walkley-Black wet oxidation

The Walkley-Black method (wet oxidation with potassium dichromate) is the traditional standard for quantifying soil organic carbon.

Which term describes the reddish or yellowish zones of iron and manganese oxide accumulation surrounding macropores in a hydric soil?

Answer: Redox concentrations

Redox concentrations are zones of accumulated iron, manganese, or sulfides, often appearing as pore linings or soft masses in high-chroma colors.

A soil classified as a Histosol must have an organic soil horizon of at least how many centimeters when the organic material is saturated for long periods?

Answer: 40 cm

For saturated organic materials, a Histosol requires an organic layer of 40 cm or more (or 60 cm if the bulk density is less than 0.1 g/cm³).