Turfgrass Study: Grow Lush Green Lawns With Less Water In Southwest

NMSU researchers studied turfgrass varieties for the Four Corners area to find out which ones make the best use of water while still providing acceptable coverage and quality green color. The study also provided data for precise lawn watering recommendations for each species, something previously lacking for northwestern New Mexico.

"We can now recommend alternative grass species with acceptable quality that use less water and are generally more drought tolerant than the Kentucky bluegrass that is so commonly grown here," said Dan Smeal, agriculture specialist with NMSU and head of the study. "For those folks who don't want to move to more water-efficient varieties, we can offer precise calculations on the minimum amount of water needed to maintain quality with the grass they are already growing. That's something that benefits everybody, from park and golf course managers to homeowners."

The project compared water use rates for several varieties of warm- and cool-season turfgrasses. Cool-season varieties such as blue grasses, rye grasses and fescues generally grow best during cooler months, allowing them to green up in early spring and retain their color until late fall. Warm-season varieties such as buffalo and Bermuda grasses grow best in the hot summer months, giving them a shorter growing season.

In 1997 researchers planted 14 grass varieties - an even mix of seven cool- and seven warm-season - and tested gradient-staggered watering levels. Growth rates for each species were recorded during 1998, 1999 and 2000. The center also invited 10 master gardeners from San Juan County, N.M., to judge grass quality during each season, rating greenness, density, uniformity, disease problems and blade texture.

Overall, the study showed the nonnative, cool-season varieties tested needed about 40 percent more water to maintain an acceptable appearance than the native, warm-season varieties. Although the study related specifically to grass grown in the test area in New Mexico, Smeal said the water savings for using warm-season grasses would likely be at the same percentage for any area of the southwest U.S.

"The shorter growing season for warm-season grasses cuts down on water use, but we also found they need less water on a daily basis to maintain acceptable quality than cool-season varieties," Smeal said. "They're just more drought tolerant, which is logical for varieties such as buffalo grasses that are native to the semiarid conditions here."

During droughts, warm-season grasses turn brown but green up again when the drought ends, Smeal noted. In contrast, stands of cool-season grasses don't survive. "They thin out and get clumpy, making recovery much more difficult," he said.

"I would recommend using the native varieties over the non-native," Smeal continued, "particularly because they’re adapted to the semiarid conditions that we have in the Southwest, and they don’t experience as much disease problems, they’re fertility requirements are lower, and the mowing frequency is generally less."

Although master gardeners gave most of the warm-season varieties acceptable quality ratings, the cool-season grasses were much greener and fuller, giving them greater appeal.

"Although the warm-season grasses use significantly less water, it will be hard to convince people not to use the greener cool-season grasses," Smeal said. "But at least now, with the data we've compiled, we can make concrete recommendations on minimum daily water use for cool-season varieties, something we couldn't do before."

Additionally, NMSU's Cooperative Extension Service has created an irrigation scheduling program that can help individuals determine watering rates for both warm- and cool-season grasses based on crop coefficients for each variety of grass included in the study. "We correlated the evapotranspiration rate (ET) that we measured at various irrigation levels with the potential ET to develop a crop coefficient for each of the grasses," explained Smeal. He noted that potential ET is calculated using weather data and is a relative value that can be used throughout the entire southwestern U.S. For instructions on how to access the online scheduling program, which Smeal said will undergo some future fine-tuning to be more user-friendly, see the sidebar at right.

Smeal suggested that landscape contractors in the Southwest educate their customers about the water savings realized by using native warm-season grasses for their yards. "Right now if customers wanted to go with cool-season grasses, I would at least urge contractors to use the irrigation scheduling program to schedule irrigations. If they’re interested in saving water - if water’s expensive, and of course, it will become more expensive in our area as the demand for the limited supply continues to increase -then I would suggest contractors look at some of the alternative warm-season grasses, which would use less water," he said.