CFA Soil Properties and Testing 2

Question 1

A soil sample has a bulk density of 1.6 g/cm³. Which condition does this most likely indicate?

Accepted Answer

Highly compacted soil with restricted root growth

Answer

Bulk densities above 1.4–1.6 g/cm³ typically indicate compaction that restricts root penetration and water infiltration.

Question 2

Which soil textural class holds the most plant-available water while still draining adequately?

Accepted Answer

Loam

Answer

Loam soils balance macropores for drainage and micropores for water retention, making them ideal for plant-available water.

Question 3

When interpreting a soil test report, a base saturation of potassium (K) at 5% is considered:

Accepted Answer

Adequate for most crops

Answer

A K base saturation of 3–5% of CEC is generally considered adequate for most crops.

Question 4

Which extraction method is most commonly used to assess plant-available phosphorus in neutral to alkaline soils in the western US?

Accepted Answer

Olsen (sodium bicarbonate)

Answer

The Olsen method using sodium bicarbonate is preferred for calcareous (alkaline) soils because it doesn't dissolve calcium phosphates.

Question 5

Soil organic matter is most accurately measured in a laboratory by:

Accepted Answer

Loss-on-ignition (LOI) or Walkley-Black wet oxidation

Answer

Loss-on-ignition and Walkley-Black wet oxidation are standard laboratory methods to quantify soil organic matter content.

CFA Practice Test