Soil Science & Analysis Flashcards

Which redoximorphic feature in a soil profile is considered a depletion rather than a concentration?

Answer: Gray zones with low chroma surrounding root channels

Redox depletions are zones where iron and manganese have been leached out under reducing conditions, leaving low-chroma gray colors.

What is the functional significance of hydrogen sulfide (H₂S) gas detected in a soil pit during a wetland delineation?

Answer: Confirms anaerobic conditions and microbial sulfate reduction

H₂S is produced by sulfate-reducing bacteria under anaerobic conditions and serves as a positive hydric soil indicator (F6 - Sulfidic Odor).

Which soil texture class typically has the highest saturated hydraulic conductivity and drains most rapidly following flooding?

Answer: Coarse sand

Coarse sand has large pores and minimal capillary tension, giving it the highest hydraulic conductivity and fastest drainage rates.

For the Histosol order, fibric organic material is defined as having what minimum fiber content after rubbing?

Answer: 17%

Fibric material retains ≥40% fibers before rubbing but the post-rubbing threshold defining fibric vs. hemic is 17% fibers by volume.

Which soil order is most commonly associated with wetland environments in the southeastern coastal plain of the United States?

Answer: Histosols

Histosols (organic soils) are abundant in southeastern coastal plain wetlands, such as the Everglades and Carolina bays, due to long-term waterlogging.

In a typical hydric soil, which horizon is most likely to show the strongest evidence of iron reduction and gleying?

Answer: A horizon

The A horizon is subject to the longest periods of saturation and biotic oxygen demand, making it most prone to gleying and redoximorphic features in hydric soils.

The alpha-alpha dipyridyl field test is used to detect which soil condition during wetland delineation?

Answer: Ferrous iron indicating active reduction

Alpha-alpha dipyridyl reacts with ferrous iron (Fe²⁺) to produce a bright red color, confirming active reduction conditions in a saturated soil.