Friday, October 24, 2014

Yes, but do they work? Putting soil moisture sensors to the test

First in a smart water application technology series.

In Florida, irrigation water-use accounts for around 50% of total household water consumption. Most of the single-family homes recently built in Florida (as well as in the U.S.) include an automatic irrigation system, which results in an increase in demand from already limited water resources. 
Save water, Florida! Courtesy: EPA WaterSense
The development of best management practices for irrigation of landscapes has become an undeniable strategic, economic, and environmental issue for the state. New soil moisture sensor systems (SMSs) for landscape irrigation control may improve irrigation efficiency, promote water conservation, and reduce environmental impacts of over-irrigation.
Sensing savings
A research project was funded by the Southwest Florida Water Management District to evaluate SMS-based irrigation systems. The main goal: to determine if SMSs could reduce the water applied, compared to common time-based irrigation schedules implemented by homeowners. At the same time, we wanted to know if these hypothetical water savings could be achieved without compromising an acceptable turf quality.

On the corner of research & technology: the plots
The experimental area (at UF research facilities in Gainesville) consisted of common bermudagrass plots (10 x 10 ft). The sensors of four commercially available SMS systems (brands Acclima, Rain Bird, Irrometer, and Water Watcher) were buried at the 7 to 10 cm depth. For comparison purposes, time-based treatments with and without a rain sensor, and a non-irrigated treatment were also implemented. 
Proper soil moisture sensor installation with Bernard Cardenas
Non-irrigated, but green
During the 2-year experiment, normal/wet weather conditions prevailed in the research area, which favored turf growth and development. As a result, no significant differences in turfgrass quality among treatments were detected, even when compared to the non-irrigated plots. This means that, for sustained normal/wet weather conditions in Gainesville, a bermudagrass turf probably would not need supplemental irrigation.

Regarding the SMS treatments, most of them recorded significant irrigation water savings compared to the time-based irrigation schedules. Savings ranged from 69% to 92% for three of the four SMS brands tested. The treatment with-rain-sensor, on the other hand, resulted in 34% less water applied than the without-rain-sensor treatment. All these water savings were achieved without decreasing turfgrass quality below acceptable levels.

Time to validate
Therefore, SMSs represent a promising technology for water conservation, even better than the rain sensors mandated by FL law. Given these results, we then sought to test SMSs under sustained dry weather conditions and in residential irrigation systems.

This research was conducted by Mr. Bernardo Cardenas, Dr. Michael D. Dukes and Dr. Grady Miller. 

Bernardo Cardenas has a M. Sc. in Agricultural and Biological Engineering, from UF. He specializes in smart water application technology research, but refuses to irrigate his own lawn.


  1. Thank you for conducting the research and publishing the results. SMS is a great water savings tool in a controlled environment, but in a real landscape soil moisture is greatly impacted by trees, solar exposure, slop and soil profile. I look forward to reading what you learned when you validate on residential irrigation systems.