Submitted to: Irrigation Today
Publication Type: Trade Journal
Publication Acceptance Date: 2/18/2017
Publication Date: 2/23/2017
Citation: Evett, S.R. 2017. Soil Moisture Sensing. Irrigation Today. 1(3)14-15.
Technical Abstract: Soil moisture monitoring can be useful as an irrigation management tool for both landscapes and agriculture, sometimes replacing an evapotranspiration (ET) based approach or as a useful check on ET based approaches since the latter tend to drift off target over time. All moisture sensors, also known as soil water sensors, measure a response to some soil property that is related to water content, then use a calibration equation to convert the measurement into a soil moisture estimate. Often the calibration is internal to the sensor or sensing system. Although individual sensors are available, the market is demanding moisture sensing systems that feed data into a central point using either wired or wireless telemetry. Sensing systems may be tied into a decision support system that further processes the data to provide an irrigation recommendation or even control an irrigation valve or system directly. The major types of soil water sensors are presented. Major impediments to use of a given sensor type are discussed, and guidance is given to make best use of a given sensor type. The major sensor types are those based on neutron counts, those that measure electrical resistance of a porous body buried in the soil, those that operate on electrical capacitance principles, and those that measure travel time of a fast electrical pulse along a conductor in contact with the soil.