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Soil-moisture Sensors May Produce Big Water Savings for Homeowners, UF Study Shows

Topic(s): Conservation, Florida Friendly, Green Living, Landscaping, Lawn & Garden

GAINESVILLE, Fla. — Soil-moisture sensors hooked to sprinkler systems could put a huge dent in homeowners’ utility bills – and help conserve much-needed water, a new University of Florida study says.

Researcher Michael Dukes found that for three of four soil-moisture sensors tested, water savings ranged from 69 percent to 92 percent, compared to grass watered without the help of sensors.

"The savings turnaround could be pretty rapid," said Dukes, an associate professor in the agricultural and biological engineering department, part of UF’s Institute of Food and Agricultural Sciences.

That’s partly because in recent years, soil-moisture sensors have become less expensive, smaller and more accurate, he said.

"The cost is changing rapidly. A few years back, a $400 list price and about $100 to install was common, but now we’re seeing products in the $100 to $200 range," he said. A typical Florida yard would require one sensor, though larger landscapes would likely need more. To get the biggest savings, the irrigation system and the sensors must be in good repair, well designed and properly installed, Dukes said.

The sensor, buried ideally in the driest part of the lawn, overrides the automatic irrigation system if the lawn doesn’t need water.

In the study, accepted for publication in the Journal of Irrigation and Drainage Engineering, IFAS researchers tested four types of rain sensors. The more recent study dovetails with an earlier one by the same researchers – published in the journal’s September-October issue – that showed homeowners could reduce water consumption by a third simply by setting their lawn-watering systems to more closely match plant needs, according to the season.

In the most recent study, each sensor was tested at irrigation frequencies of one, two or seven days a week. The one- and two-day watering frequencies most closely resemble typical watering restrictions in Florida.

Data was collected from July 20 to December 14 of 2004 and March 25 to August 31 in 2005.

On average, studies have shown that U.S. homeowners use about 50 percent more water outdoors than indoors. And water officials say lawn irrigation accounts for nearly half the potable water used in South Florida.

Taking the human component out of the watering process certainly seems to help reduce overwatering, said Kathy Scott, section manager for conservation projects with the Southwest Florida Water Management District, which sets water policy for some 4.5 million residents.

But Scott said her agency remains cautious and not quite ready to urge homeowners to run out and buy a soil-moisture sensor just yet. That may happen, though, after more study of homeowners’ watering habits.

"We are going to end up with a whole list of best management practices, so that we’ll be able to tell people exactly how to use the sensors," she said. "We know they save water, we know that. But what we don’t know is what happens when the dial is in the homeowner’s hands."

Many residents don’t realize how little irrigation most lawns need, she said. Often, those trying to start a new lawn take advantage of less-restrictive watering rules – unwittingly giving their new lawn a poor start.

"If you water too much, the roots don’t have any incentive to grow deep, so you end up with a lawn that’s weak, susceptible to pests, disease and has shallow roots," Scott said.

It just seems to be human nature to overdo it, she said.

"My sense, from talking to people about this, is that they think if a little water’s good, a lot is better."

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