Question

The pF range of soft or friable consistency of soil is:

• A. More than 4.5
• B. 2.8–4.5
• C. 0.5–2.8
• D. Less than 0.5

Hint:

Remember typical pF values corresponding to soil consistency for field condition analysis.

Answer 1

The Correct Option is C

Friable soils generally fall within the pF range of 0.5–2.8, indicating optimum moisture conditions for tillage.

Answer 2

Working from the pF scale definition:
The pF value is defined as the base-10 logarithm of soil-water suction expressed in centimetres of water: \[ pF = \log_{10}(h_{cm}) \] Very wet, nearly saturated soils correspond to pF values below about 0.5, where the soil is fluid or viscous. As suction rises through the range roughly \( pF = 0.5 \) to \( pF = 2.8 \), the soil passes through sticky and plastic behaviour into the moist, easily crumbled condition known as friable or soft consistency, a range that brackets field capacity. Beyond about \( pF = 2.8 \), up to around \( pF = 4.5 \), the soil is dry enough to become hard, and above \( pF = 4.5 \) it approaches the permanent wilting point and beyond. Placing friable or soft on this scale therefore corresponds to \( pF = 0.5 \) to \( 2.8 \), confirming option 3.