Basically sensors are used to measure water content in the soil. A thorough probe into the soil moisture conditions are in fact done by a group of sensors. These sensors include sensors measuring frequency domains, known also as capacitance sensors. In order to make use of some properties of water for neutrons, there are neutron moisture gauging sensors, and sensors also used how far soil can resist the electrical discharges.
TDR and TDT (or time domain reflectometer and time domain transmission) help ascertain the presence of high dielectric constant in the water. There are also sensors for heat dissipation, which depend on the insulation or R-Value of the soil. It is common knowledge that when soil has additional water content gets heated up faster than the dry soil.
For agricultural operations, the measuring of soil for its water content is of utmost importance. This helps the farmers to plan their irrigation needs and ensure that only the required quantity of water is used. Thus they will be using less water quantities, but grow more crops, besides increasing the yield of crops. Soil water content knowledge helps farmers to manage the growth of plants at every stage and monitoring the crop becomes easier.
Sensors to measure soil water content are used in a number of activities besides farming. In urban areas, as well as some developed semi-urban regions, for lawns in the front and backyards of residences, the soil sensors are used to determine the type of lawns, and water required for such lawns.
Most amazingly, even golf courses are known to use sensors to ensure that their irrigation methods of growing grass in the course is better managed through the knowledge of water content and the nature of the soil. In such situations soil measuring sensors become a sort of interface with irrigation controlling systems. When you connect the sensor to an irrigation clock, it can become a smart controller of irrigation, which plans a cycle for irrigation, ensuring that when there is wetness in the soil, irrigation can be deployed.