Soil moisture sensor
Soil moisture sensors measure the water content in soil. A soil moisture probe is made up of multiple soil moisture sensors.
Technologies commonly used in soil moisture sensors include:
- frequency domain sensor such as a capacitance sensor.
- neutron moisture gauges, utilize the moderator properties of water for neutrons.
- electrical resistance of the soil
- Time domain transmission (TDT) and time domain reflectometry (TDR); water has a high dielectric constant; a higher water concentration causes a higher average dielectric constant for the soil. The average dielectric constant can be sensed by measuring the speed of propagation along a buried transmission line.[1][2]
- heat dissipative sensor; Heat dissipation sensors rely on the effective heat R-value (insulation) of soil. Soil with additional water conducts heat more readily than dry soil. [3]
Agriculture
Measuring soil moisture is important in agriculture to help farmers manage their irrigation systems more efficiently. Not only are farmers able to generally use less water to grow a crop, they are able to increase yields and the quality of the crop by better management of soil moisture during critical plant growth stages.
Besides agriculture, there are many other disciplines using soil moisture sensors. Golf courses are now using sensors to increase the efficiencies of their irrigation systems to prevent over watering and leaching of fertilizers and other chemicals offsite.
Landscape irrigation
In urban and suburban areas, landscapes and residential lawns are using soil moisture sensors to interface with an irrigation controller. Connecting a soil moisture sensor to a simple irrigation clock will convert it into a "smart" irrigation controller that prevents an irrigation cycle when the soil is wet.