Campbell Scientific has an array of soil temperature sensors that are compatible with their dataloggers and weather stations. Several of these sensors can be buried at different depths and attached to a single station. The data can then be collected and transmitted in real time via radio or internet to your computer or phone.
Sentek Technologies offers a suite of soil monitoring probes that measure soil moisture, temperature, and salinity at multiple depths concurrently. The data can be collected manually, or broadcast over radio or internet to your computer.
Onset also offers an array of temperature sensors, much like Campbell Scientific. Onset’s Smart Sensors feature plug-and-play functionality, so sensors can be attached to the weather station with no programming required. The data can also be transmitted via internet in real time.