New soil moisture sensors have the ability to provide automatic irrigation controllers advanced water conservation methods when the sensor accuracy falls within guidelines described in this presentation. Previously there have been no standards set for the sensor accuracy needed or the controller requirements for irrigation water management. Key issues that concern water management are practical irrigation water application with a single in-situ sensor for multiples zones, how to manage for maximum efficiency, and how to project water savings. Multiple sensors with multiple zone irrigation controls have similar requirements and solutions needed.

The Smart Water Application Technology (SWAT) team of the Irrigation Association developed a new standard for soil moisture sensor testing protocol. The testing protocol was applied to the SM200 soil moisture sensor designed by Delta-T Devices (Cambridge, UK). Random samples of the device were tested across a series of soils, salinity, and temperate conditions by the Center for Irrigation Technology (CIT, California State University, Fresno).

Results for the SM200 soil moisture sensor are shown from the SWAT testing protocol. Performance needs for successful soil sensors in an automatic irrigation controller are explained in both absolute accuracy and data correlation required. The presentation projects the performance of controllers employing a high performance sensor across the range of soil types, the salinity effects, and temperature effects on the sensors performance. The sensor results indicate that the irrigation controllers may target 95 to 100 % water management efficiency, however an integrated test of controllers together with sensors has not been developed for a practical field or simulation test for industry standardization.

Key words: Soil moisture sensor, water conservation, irrigation control