Subtopic: Measurement of infiltration, soil moisture and irrigation water infiltration
Question Statement:
A vacuum gauge tensiometer installed in an agricultural field is practically limited to measuring soil matric suction up to approximately:
Options:
(A) $0.8\text{ bar}$ ($80\text{ kPa}$)
(B) $3.0\text{ bar}$ ($300\text{ kPa}$)
(C) $8.0\text{ bar}$ ($800\text{ kPa}$)
(D) $15.0\text{ bar}$ ($1500\text{ kPa}$)
Answer Key:
A
Step-by-Step Solution & Explanation
Tensiometers operate by establishing hydraulic equilibrium across a porous ceramic cup. At suctions above $0.8\text{ to }0.85\text{ bar}$ ($80\text{ to }85\text{ kPa}$), dissolved air bubbles come out of solution (cavitation) and break the water column.