CPESC Soil Science 3

Question 1

What is the primary mechanism by which organic matter improves soil erodibility?

Accepted Answer

Binding soil particles into stable aggregates

Answer

Organic matter acts as a binding agent through compounds like glomalin and humus that cement soil particles into water-stable aggregates resistant to raindrop impact.

Question 2

In the context of soil erosion, what is 'rill erosion'?

Accepted Answer

Erosion forming small, defined channels on a slope that can be removed by tillage

Answer

Rill erosion creates small defined channels caused by concentrated flow that are still shallow enough to be obliterated by normal tillage operations.

Question 3

A soil bulk density of 1.8 g/cm³ in a sandy loam would most likely indicate:

Accepted Answer

Severe compaction restricting root growth

Answer

Sandy loam soils with bulk densities above 1.75 g/cm³ are considered compacted, restricting root penetration and reducing infiltration rates.

Question 4

Which process describes the downslope movement of water-saturated soil material in a slow, plastic flow?

Accepted Answer

Earthflow

Answer

An earthflow is the downslope movement of water-saturated fine-grained soil that moves in a plastic, viscous manner, often faster than creep but slower than a mudflow.

Question 5

In soil texture analysis, the hydrometer method is used to determine:

Accepted Answer

The percentage of clay and silt by settling velocity differences

Answer

The hydrometer method measures suspension density over time as particles settle by gravity, allowing calculation of clay and silt fractions based on Stokes' Law.

(CPESC) Certified Professional in Erosion and Sediment Control Practice Test

(CPESC) Certified Professional in Erosion and Sediment Control Practice Test

CPESC Soil Science 3