The American Society of Agricultural and Biological Engineers (ASABE) recently released a new standard for testing soil moisture sensors used to control landscape irrigation. The new standard has been published as ANSI/ASABE S633 Testing Protocol for Landscape Irrigation Soil Moisture-Based Control Technologies. This standard defines a procedure to test a soil moisture sensor and interface device’s response to changes in soil moisture conditions. The test procedure covers soil water content (volumetric) and soil water tension (matric potential) sensors.

The new standard provides a method using two different soil media — one to represent moderately coarse soils such as sandy loam and the other to represent moderately fine soils similar to a silty clay loam or clay loam soil. The soil moisture sensors are tested at three water depletion levels and two water salinities in each soil type to determine if the sensor and the associated interface device will enable/disable an irrigation event at preset or selected soil water values in a consistent, repeatable and reliable manner.

Typically, these soil moisture sensors and interface devices are meant to be used with an existing controller and to prevent or disable planned irrigation events when adequate soil moisture is present. While these products have been available in the marketplace for a long time, compliance with this testing standard provides some assurance that the products do work when installed and managed correctly.

Tom Penning, president of Irrometer Company and member of ASABE, served as the committee chair for this standard. Penning thanked the committee members including IA Industry Development Director Brent Mecham, CID, CLWM, CIC, CLIA, CAIS, and the various labs for doing trial testing, which included the Center for Irrigation Technology, Texas A&M and Florida State University. Richard Harris, who recently retired from East Bay Municipal Utility District in California, helped secure funding for the testing and provided guidance during the development of the standard. As noted by Penning, “While a long time in the making, this standard provides a basis for the EPA’s WaterSense specification to certify and label soil moisture sensor-based irrigation control devices.”

To obtain a copy of the standard, contact ASABE headquarters at orderstandard@asabe.org.