The Irrometer Company was founded in Riverside, CA in 1951. While at the Citrus Experiment Station at the University of California Riverside in the late 1940's, inventor Tom Prosser witnessed crude, homemade tensiometers in use and immediately saw the potential for farmers to use these instruments as tools for scheduling irrigation. Prosser set about designing user friendly, robust versions of these homemade instruments which could be economically manufactured for sale, and in 1951 the “Irrometer” (or “irrigation meter”) was born, fulfilling Prosser’s vision of a commercially available tensiometer.

In 1953, Sheldon Pooley, the son of a local citrus grower who was one of Prosser’s first customers, joined the Company as its Sales Manager and began the growth of The Irrometer Company worldwide.  In the late 1980’s, the Company expanded its product line with the addition of the Watermark soil moisture sensor which it acquired from its inventor, Glenn Larson. Sometimes referred to as the most important development in soil moisture measurement since the original Irrometer, the low cost and reliable technology of the Watermark sensor has made a major impact on the large scale use of soil moisture measurement technology by production agriculture throughout the world. With the development of electronic interfaces for automated irrigation systems used in landscape irrigation, the use of Watermark sensor technology now has become one of “SMART” irrigation system technologies. Water purveyors and the EPA are embracing the concept of “SMART” irrigation systems as a means to prevent the overuse of water in landscape irrigation.