Irrometer Model SR Soil Moisture Tensiometer-12-Inch #212

Recommended by the USDA and local water conservation districts, the Irrometer Model SR Tensiometer is a simple, accurate, and reliable way to control irrigation scheduling and maximize water resources. They consist of a water filled tube sealed with a vacuum gauge and replaceable porous tip. The vacuum gauge measures in Centibars (kPa) from 0 (completely saturated) -100 (totally dry), with a normal operating range above 30 Centibars (kPa)***. In dry soil, water is drawn out of the Tensiometer creating a partial vacuum that's registered on the gauge. The drier the soil, the more pressure, the higher the reading. The wetter the soil, the less pressure, the lower the reading. In this way, Tensiometers act as a virtual root system, measuring how hard plants work to extract moisture, regardless of whether they're planted in sandy or clay soil. They're installed two at a time, one in the upper root zone and one in the lower root zone. The upper root zone determines when to irrigate and the lower root zone helps adjust irrigation amounts and system run-times. After installation, gauges are read 2-3 times between irrigation cycles. These readings tell how fast a crop is extracting water and when there's a need to irrigate. They can also be used to record / chart readings or to control / interrupt irrigation cycles that aren't needed. Service kit required for first time installations. Made in the USA.

*** For conditions where readings above 30 centibars (kPa) are not expected, i.e. container media mixed with peat, bark, sand, perlite and vermiculite, or soils with large sand particles, such as Florida's “coral sand,” or Washington's “blow sand”, Irrometer Model LT Tensiometers are recommended.