Soil water matric potential is often measured using tensiometers that have a maximum range of −80 kPa limited by the vapor pressure of water which is significantly below the range where many drought tolerant plants grow and they require regular refilling and degassing after a dry period . In contrast resistive soil moisture tensiometers like the Watermark®
soil moisture sensors are responsive to soil potentials in excess of −200 kPa. We decided to use Watermark® sensors because of their low cost, ease-of-use, and because they are widely used by the agricultural community for scheduling irrigation. Some researchers have evaluated Watermark® sensors and found them to respond well to the
wetting and drying cycles for most soil types