The Use of Soil-Water Sensors in Turf Irrigation Control — How Effective Are They?

Soil-Water sensor controllers have been used since the mid-1990s to manage turf irrigation. While evapotranspriation (ET) based controllers have been more widely adopted for turf and landscape irrigation, soil-water-sensor based systems hold some distinct advantages, particularly in humid regions where rainfall contributes significantly to turf water requirements and is highly spatially variable. Some perceived disadvantages of soil-water-sensor based systems are representativeness of whole landscapes when only one sensor is used; sensor accuracy and repeatability, and proper setting of soil-water setpoints. Several studies involving soil-moisture sensors have been done in Florida, and one study in North Carolina is near completion. These studies have looked at soil-water sensor based systems of various manufacturers in similar settings; have compared results between different moisture setting thresholds; have contrasted water usage with ET based controller systems; and have monitored root zone soil-water status in plots irrigated by soil-water based systems. Soil-water data has also been collected for replicates of sensor-based treatments in an effort to address the question of repeatability and sensor placement representativeness. Preliminary data from these studies have shown that there is wide variability between different sensor systems with respect to both applied water and turf quality. The data has also shown that soil water sensor based systems may in some cases apply less water than ET controllers. Consistent relationships between soil-water-content and controller settings has been found to be problematic. Analysis of soil-water data indicates that while there are differences in soil-water between replications of soil-water-based sensor treatments, soil-water trends are generally consistent between replications and turf quality is generally not substantially different between replications.