A highly accurate portable TDR sensor that measures soil moisture content (volumetric %).
Time Domain Reflectometery (TDR) is one of the most accurate methods of measuring soil moisture content as a percent. Costs for this technology have reduced significantly over the last few years making it available to a much wider base.
The HydroSense II is a portable sensor that measures soil moisture content (%). It also has an integral GPS which allows storage of multiple measurement points against their respective farm locations. This can be viewed on the display, or downloaded via Bluetooth to computer for integration with Google maps.
In addition, site specific values can be set in the device which will calculate the soil water deficit in mm, allowing the user to determine irrigation requirements.
The principle of measurement is based on the high "dielectric constant" of water. This is about 20 times that of dry soil, so when a wave guide (the 2 parallel probes) is inserted in the soil, the dielectric constant of the wet soil (a combination of soil & water) can be measured accurately, and from this, the % water content of the soil. Fortunately, understanding the physics of the measurement is not required for this to be a very useful tool for soil moisture management!