Measurement and monitoring of soil moisture is becoming commonplace for irrigation management and to quantify drainage. In some crops wireless soil moisture monitoring using soil moisture sensors that continuously measure soil moisture and telemeter the measurements to a web base are suitable. Not all sensors are the same, so how do you choose and get the best from sensors?
There are many companies making soil moisture sensors to measure the soil’s dielectric constant and convert to volumetric water content (V%). All of the sensors are sensitive to both soil temperature and salinity (conductivity). Temperature and conductivity are simple to measure (easier than soil moisture), but the relationship with V% is complex.
All sensors measuring the dielectric constant require calibration to read volumetric soil moisture. The calibration could be a universal “factory calibration”, one based on soil texture (e.g. sand, silt or clay) or most preferably a field calibration.
HydroServices has been testing and using dielectric sensors in various locations for a number of years. Every sensor measures a different volumetric soil moisture content – even at the same location. HydroServices expertise and experience has found the factory calibration does not provide an accurate soil moisture measurement. Field calibration is needed and essential.
Sites installed by HydroServices are field calibrated to obtain accurate volumetric soil moisture (V%). Field Capacity (or Full Point), Available and Readily Available Water, Saturation and Wilting Point are determined by HydroServices