Calibration of the 10HS Soil Moisture Sensor for Southwest Florida Agricultural Soils

Precision irrigation is crucial in decreasing water demands of irrigated agriculture, which account for the largest source of water withdrawal in most regions. One necessity of precision irrigation is the knowledge of soil moisture content in the root zone of irrigated crops. Dielectric soil moisture sensors can provide this information at a relatively low cost ($100) compared with other techniques; however, their accuracy cannot be guaranteed in all soils without site-specific calibration, the need for which has limited the use of these sensors. This study examined the Decagon 10HS soil moisture sensor in order to determine the accuracy of the manufacturer-supplied calibration equation on southwest Florida (SWFL) agricultural soils, and analyze whether it performs consistently in different soils found in SWFL. Laboratory calibration of the 10HS was done on four SWFL soils that represent the majority of agricultural land in the region and regression calibration equations were obtained. It was found that the manufacturer calibration equation does not accurately predict soil volumetric water content (VWC) within the +/- 3% accuracy range specified for the sensor, meriting the need for site-specific calibration. Additionally, it was found that all tested soils behave very similarly, allowing the development of a single calibration equation for use of the 10HS in all SWFL agricultural applications. The calibration equation developed during this research for SWFL could allow a more widespread use of the 10HS in the region. (C) 2013 American Society of Civil Engineers.