Soil Tensiometer directly measure Soil Suction the force that plants have to overcome to get needed water, the force that determines which way moisture will move in the soil. Consisting of a tube with a porous ceramic tip at the bottom, a vacuum gauge, and a sealing cap, the "Bellstone" Tensiometer is first filled with water and inserted into the soil. It registers the vacuum created when water drains out, therefore, as the soil dries out, the vacuum gauge dial moves.
The reverse happens when there is moisture in the soil. By a process of osmosis water enters the Tensiometer, lowering the vacuum. It shows on the gauge as decreasing soil moisture Tension. When the moisture in the soil attains saturation, the pointer in the vacuum gauge will show zero. Durable and dependable, these Tensiometers offer a host of advantages compared to other methods of measurement of soil moisture-such as electrical resistance measurement or neutron probes :
• Direct continuous measurements
• No Calibration required
• Much greater precision
• No power source required, or electrical leads
• less cumbersome
• Portable, with simple field-replaceable parts
• For all types of soil conditions
