Hornbuckle (IMAGE) Iowa State University Caption One of the instruments Brian Hornbuckle uses to measure soil moisture content is a microwave radiometer. Credit ISU photo by Bob Elbert. Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.