What is the Soil tensiometer principle of operation?

1. Soil water exists as thin film around and between soil particles and is held by strong molecular forces.
2. As soil dries, water films become thinner and more tightly bound to the soil particles.
3. The increased tension within the films in contact with the ceramic tip causes water to be drawn out.
4. The water withdraw continues until the vacuum created inside the tension equals the tension of the water film outside i.e. equilibrium point is reached and water ceases to flow out.
5. The vacuum gauge reading indicates the amount of suction or tension.
6. When water is added to the soil from irrigation or rainfall, the soil suction is reduced.
7. The higher vacuum in the tensiometer causes soil water to be drawn in and this decreases the vacuum until the equilibrium.
8. The tensiometer continuously responds and maintains a balance (equilibrium) with soil water suction or tension. And the vacuum gauge indicates the amount of tension hence the name tensiometer.