Calibration of Soil Moisture Sensors Using Pedotransfer Functions.

Obtaining accurate soil moisture data from a sensor network relies on sensor calibration. Soil moisture sensors are factory calibrated, but multiple site specific factors may contribute to sensor inaccuracies. Thus, sensors should be calibrated for the specific soil type and conditions in which they will be installed. Lab calibration of a large number of sensors prior to installation in a heterogeneous setting may not be feasible. We have developed a correction that could be applied to sensor data that incorporates inherent site characteristics and soil variability. We used a pedotransfer function to estimate the saturation, field capacity, and wilting point at multiple depths in instrumented soils; these values were then used to correct sensor readings. The correction was assessed with volumetric water content measurements obtained from field-sampled cores taken on multiple dates, and we have identified points for improvement. This approach may serve as an alternative method for sensor calibration when pre-installation calibration of sensors is not possible.