Attached is a new application note that includes a process for calibrating soil moisture data. This same process can be used to verify the 3% accuracy of the W-SMC soil moisture sensors. The installation of the sensors is really critical to the accuracy of the soil moisture measurement and this may explain the variability they are seeing. I also have to question if when they apply the water in the field if the soil moisture at the sensor is really what they think it is. To get really controlled soil moisture samples, they need to follow a process like the one in the application note.