Published on 01/25/07

Researcher finds way to halve greenhouse water use

By Stephanie Schupska
University of Georgia

The well could eventually run dry. The water from a city main could stop flowing. As Georgia’s population keeps increasing -- up more than 25 percent from 1990's numbers -- so does the demand for water. A University of Georgia professor is looking for ways to preserve this resource.

Marc van Iersel, a horticulture professor in the UGA College of Agricultural and Environmental Sciences, focuses on managing greenhouse irrigation.

For growers who use thousands of gallons of water a day, controlling their irrigation can be critical. And Van Iersel is researching ways to make it easier.

“We’re putting plants in charge of their own irrigation,” he said.

In his greenhouse, a soil-moisture sensor placed in each of 16 test containers sends a signal to an irrigation system when the moisture drops below a certain percentage. Later, he and fellow researchers can translate these numbers to advise growers of the best amount of water to use.

“That way, we can water plants based on the amount they really need,” he said.

Growers commonly test a plant’s water needs by the finger-poke method or by irrigating on a timer. Neither technique is very precise. Van Iersel figures growers could save up to 50 percent of irrigation water by using an automated approach like the one he’s researching.

“One greenhouse in Georgia spent $50,000 a year on electricity to pump water on plants,” Van Iersel said. “It takes a lot of power because water is heavy.”

Using less water would significantly increase greenhouse growers’ profits. And as new greenhouses open and older ones expand to meet homeowners’ and businesses’ needs, the water supply available to them is subject to increasing demand.

“We need to learn to use water as efficiently as possible,” Van Iersel said. “As long as the state keeps growing, the urban areas will get all the water they want, leaving less for the rest of the state.”

Georgia really doesn’t have enough water to support both the growing population and agriculture industries, he said.

Another water concern specific to greenhouses is runoff. When growers irrigate, they feed their plants through fertilizer added to the water. If they use more water than needed, the fertilized water runs out of containers and eventually onto the ground.

Over time, the U.S. Environmental Protection Agency will tighten its restrictions to prevent environmental impact. For greenhouse growers, keeping water in the pots could help meet these standards.

The system Van Iersel has developed isn’t complicated. “We can always use a really fancy system to do our research. But I’m more interested in doing something that can be used by growers,” he said.

“We’re really close to being able to implement this approach. Seeing that this system will make it to the greenhouse industry in the next few years makes it exciting.”

In the future, the system may have even broader applications. “People can use it anywhere they water,” he said. “With lawn irrigation, specifically, if someone used a system like this, it could put them in compliance with state water restriction standards. Homeowners are often the worst offenders.”

Van Iersel has been working with Brower Electronics Laboratories to develop an irrigation controller as an add-on to existing irrigation systems that can be automated through existing computer programs.

(Stephanie Schupska is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.)

Stephanie Schupska is the communications coordinator with the University of Georgia Honors College.