Story by Zachary Ziegler and Mary Olivas

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Karsten facility

Photo: Zachary Ziegler

University of Arizona scientists are working to help one of Arizona’s major tourism industries be friendlier to the desert environment.

With more than 40 golf courses in the Tucson area alone, and many more statewide, Arizona’s Golf Industry Association is responsible for an estimated $3.5 million of the state’s economy and nearly 20,000 jobs.

Maintenance of all that grass can be a major drain on the area’s limited water supply.

Paul Brown from the UA's Karsten Turf Grass Research Facility is trying to find a solution.

A few years ago, Brown and the rest of the team at the Karsten started a study to look at how various turf grasses would perform under less than optimal irrigation rates.

rows of grass dying

Photo: Zachary Ziegler

The rows of grass in the experiment die off at varying rates of water stressing.

They hope their research will help Arizona keep the money, jobs and scenery that the grass brings without using more water than necessary.

“We can get down to around 75 percent of optimal irrigation and the grass still looks pretty good,” Brown said.

He experiments with seven varieties of grass: four kinds of Bermuda grass and three new types of paspalum, which could someday take the Bermuda’s place.

For the research, Brown uses a linear grading irrigation system. It waters grass so the area near the sprinkler heads gets more water than those further out.

grass flags

Photo: Zachary Ziegler

The plots of grass gradually decreases in water from 125% of the optimal amount of water at the top to 50% at the bottom.

However, Brown said, hydration is not the only problem.

He said that, as irrigation water is applied, salt from either surface water or ground water is also applied.

“These are dissolved salts that are naturally in the water supplies,” Brown said. “They are not removed by the plants sufficiently enough to eliminate them...salts will slowly build up over time.”

This causes a problem because salt keeps water from getting into the soil, and is a mineral the plants don’t need. Too much salt on the ground will eventually kill the plants, meaning they need to be diluted periodically by rain.

Since the salt comes from ground water, using less of it means there is less salt to be washed away.

This would be helpful to cities, such as Yuma and Phoenix, which are much drier than the Tucson area.

Dying grass rows

Photo: Zachary Ziegler

The grasses in the experiment start showing that they lack water around 75% of optimal amounts.

The Bermuda grasses seem to hold up well with less water, however the paspalums appear to need something closer to the optimal amount.

The paspalums also deal with salt better, making them better suited to drier climates that don’t have as much rain to wash away salt. But Brown said they need more time to do research.

“The truth is that salt levels are not high enough in these deficit zones to seriously damage the growth of Bermuda grass or paspalum,” Brown said. “We just haven’t gotten there and that’s why this needs to be a longer-term study.”