Unlike other soil moisture sensors, the Hydra probe obtains soil moisture by simultaneously measuring the dielectric constant and conductivity. The dielectric constant and conductivity have a great influence on the parameter of soil moisture: the dielectric constant is the most direct indicator of water content, and the conductivity also depends largely on the soil salinity. The unique multi-parameter sensor with a measuring principle has an extremely compact and rugged housing, which can simultaneously measure soil moisture, soil temperature and soil conductivity. Unlike other soil moisture sensors, the Hydra probe obtains soil moisture by simultaneously measuring the dielectric constant and conductivity. Dielectric constant and conductivity pair