CH Soil Science & Analysis 2

Question 1

Which soil property is most directly used to estimate saturated hydraulic conductivity (Ksat) in the field?

Accepted Answer

Soil texture and structure

Answer

Soil texture and structure control pore size distribution, which is the primary determinant of saturated hydraulic conductivity.

Question 2

In a soil profile, a 'fragipan' horizon is best described as:

Accepted Answer

A brittle, dense subsurface layer that restricts root penetration

Answer

A fragipan is a dense, brittle subsurface horizon that appears cemented when dry but slakes in water, restricting roots and water movement.

Question 3

Which of the following best describes the concept of 'field capacity' in soils?

Accepted Answer

The water content remaining after free drainage has ceased under gravity

Answer

Field capacity is the water content held in soil after excess water has drained away under gravity, typically measured 1–3 days after saturation.

Question 4

The 'permanent wilting point' of a soil is most commonly defined at a matric potential of approximately:

Accepted Answer

-1.5 MPa

Answer

The permanent wilting point is conventionally defined at -1.5 MPa (–15 bars), the pressure at which most plants can no longer extract water.

Question 5

Which laboratory method is most commonly used to determine the particle-size distribution of fine-grained soils?

Accepted Answer

Hydrometer analysis

Answer

Hydrometer analysis measures the rate at which particles settle in water to determine the proportion of silt and clay in fine-grained soils.

(CH) Certified Hydrographer Practice Test