Skaha's Dryland Soil Moisture Sensor Taking Shape

We have been significantly re-designing and improving our P-Band (450 MHz) microwave soil moisture sensor. This new version is considerably more accurate, sensitive, and, most importantly, has added robustness against human-made radio interference. Also, to make the instrument more comfortable to use in the field, we now have a friendly user interface that runs on Windows. It displays the sensor status in real-time - all using regular WiFi for communication. By going down to P-band frequencies, we achieve a high sensing depth of about 50 cm in most soils, which is crucial for measuring actual root-zone soil moisture. But operating at such low frequencies means lots of radio noise from nearby electronic devices, which has been limiting the usability of our technology. We now have developed a promising solution that has shown to be removing 90% of the interference. Once confirmed in the field, this will allow us to install the sensor to different types of vehicles, such as sprayers and harvesters. Those machines have presented the most challenging environments for microwave remote sensing so far. Beginning next spring, we will be mapping water productivity for farmers in Western Canada. Water productivity is the biomass produced per unit of water used. It is an objective measure of the productivity of any crop production system. Knowing pre-seeding and post-harvest soil moisture is essential to learning how much water was used up by the crop and calculating water productivity. This work will be done by FarmVu (, @FarmVu).

Soil moisture map overlaid on elevation.

Figure 1: The image above shows soil moisture overlaid on elevation. The elevation data were collected with the built-in GPS receiver as a by-product and later corrected in post-processing using data from the Canadian Digital Surface Model.

Water potential process.

Figure 2: The screenshot above shows an example calculation of water productivity based on post-harvest soil moisture and yield data. Red areas in the water productivity map indicate regions where productivity was low given the amount of water available for growth.

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