Umwelt-Geräte-Technik GmbH
| Eberswalder Str. 58 | D-15374 Müncheberg | phone: +49 (0) 33 43 2 - 89 575 |
2.2.
What Are Tensiometers Used For?
The tension corresponds to the force which a plant has to apply via the roots to extract water from
the soil pores. Among other applications, tensiometers can be used for irrigation control and for
evaluations of global warming impacts on ecosystems. The difference between the tensions at two
points within the soil acts as the driving force for soil water transport. Determining this gradient by
using tensiometers enables the evaluation of water movement in the soil regarding flow direction
and velocity. Tensiometer measurements are essential for the comprehensive analysis of the
water balance of a region or an ecosystem.
2.3.
How Does a Tensiometer Work?
A Tensiometer consists of an air-tight sealed, water-filled measurement volume, a unit where the
pressure transducer is located, and a porous cup, usually made out of ceramic. The pores of the
ceramic cup are filled with water and connect the water of the measurement volume inside the
tensiometer with the water in the soil outside the tensiometer. By connecting the two water
bodies the pressure conditions inside the tensiometer are always adjusted to the pressure
conditions of the water in the surrounding soil. If the soil dries, water will flow through the pores
of the porous tensiometer cup from the measurement volume into the soil, thereby creating a
negative pressure inside the tensiometer.
Water
Porous Cup
Soil Particle
Air
Water
Schematic representation of the functional principle of a tensiometer
