Tensiometer
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A tensiometer is a device used to determine matric water potential <math>\Psi_m</math> (soil moisture tension), an indirect measure of soil water content. The tensiometer consists of a glass or plastic tube with a porous ceramic tip. It is filled with a liquid, usually colored water. At the top of the tube is a vacuum gauge to allow visual inspection or a transducer to allow analog or digital inspection or logging. The device is buried in the soil, and a hand pump is used to pull a partial vacuum. As water is pulled out of the soil by plants, the vacuum inside the tube increases and can be measured by the gauge. As water is added to the soil, the vacuum inside the tube pulls moisture from the soil and the reading on the gauge will decrease. The actual reading will vary according to the type of soil, the moisture content, and due to hysteresis, according to the saturation history of the soil.
Tensiometers are used in irrigation scheduling to help farmers and other irrigation managers to determine when to water. In conjunction with a water retention curve, tensiometers can be used to determine how much to water. With practice, a tensiometer can be a useful tool for these purposes. Tensiometers can also be used in the scientific study of soils and plants.
See also
Template:Unreferenced Template:Tool-stubde:Tensiometer tr:Tansiyometre