Question

Which of the following statement(s) is/are true for tensiometer?
(A) It measures soil water potential.
(B) It is simple in operation and very useful for scheduling irrigation.
(C) It can also be used for measuring soil water flux.
(D) Although limited to &lt: 1 bar matric potential, this range can be increased by increasing the permeability of its porous cup.

• A. (A), (B) and (C) only.
• B. (A), (B) and (D) only.
• C. A) and (D) only.
• D. (D) only.

Hint:

Tensiometers are best for monitoring water availability in the field, especially in the range close to field capacity.

Answer 1

The Correct Option is A

Tensiometers are used to measure soil water potential (A) and are commonly used for irrigation scheduling (B). While limited to $<$ 1 bar, improvements in porous cup design can extend their use (D). They are not suitable for directly measuring water flux (C).

Answer 2

Testing each statement independently: (A) is true, a tensiometer's water-filled tube and vacuum gauge directly register soil matric (water) potential.
(B) is true, its readout needs no calculation and gives an immediate signal for irrigation timing, making it a standard field scheduling tool.
(C) is true, when tensiometers are installed at two different depths, the difference in their hydraulic head readings gives the hydraulic gradient, which combined with the soil's hydraulic conductivity through Darcy's law yields the soil water flux, so paired tensiometers are in fact used to estimate flux.
(D) is false, the roughly 1 bar ceiling comes from cavitation, air entering once tension nears the bubbling (air-entry) pressure of the porous cup, and this cavitation limit is not overcome by making the cup more permeable, a more permeable cup only responds faster, it does not extend the pressure range.
With (D) eliminated, statements (A), (B), and (C) remain correct.