Question

The pF curve is same as:

• A. Moisture-density relation
• B. Soil temperature-water content relation
• C. Soil pH-base saturation relation
• D. Soil water content-matric potential relation

Hint:

Important pF values to remember:
- Field Capacity: \( \text{pF } 2.53 \) (approx. \( -0.33 \text{ bar} \))
- Permanent Wilting Point: \( \text{pF } 4.18 \) (approx. \( -15 \text{ bar} \))
- Hygroscopic Coefficient: \( \text{pF } 4.50 \) (approx. \( -31 \text{ bar} \))
- Oven Dry: \( \text{pF } 7.00 \) (approx. \( -10,000 \text{ bar} \))

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The energy state of soil water determines its availability to plants and its movement through the soil profile.
The relationship between soil water content and soil water suction (tension) is represented by a characteristic curve.
Schofield (1935) introduced the term "pF" to express soil water suction on a logarithmic scale.

Step 2: Detailed Explanation:
The term "pF" is defined as the common logarithm of the soil water suction expressed as the height of a water column in centimeters:
\[ \text{pF} = \log_{10} (h) \]
where \( h \) is the soil water suction head in centimeters of water.
The pF scale ranges from 0 (saturated soil, suction head \( = 1\text{ cm} \)) to 7.0 (oven-dry soil, suction head \( = 10^7\text{ cm} \)).
A plot of soil water content (horizontal axis) against the corresponding pF values (vertical axis) is called a pF curve.
This curve represents the relationship between the volume of water retained in the soil and the force (tension/matric potential) holding that water.
It is also referred to as the soil moisture characteristic curve or the soil water retention curve.
Therefore, the pF curve represents the soil water content-matric potential relation.

Step 3: Final Answer:
The pF curve is another term for the soil water content-matric potential relation.