Writer: Norman Martin
LAS CRUCES - New Mexico State University scientists studying turf irrigation have discovered how a series of 5-by-5 foot trays buried a foot below ground can cut water use in half. The work sheds new light on a puzzle that has long intrigued New Mexicans: How can desert dwellers have a lush lawn or golf course?
An international research group headed by Bernhard Leinauer, an NMSU turfgrass specialist, has found that a subground irrigation technique, Evaporative Control Systems, used the least amount of water while providing the highest quality turf. The two-year study examined three water application methods here on the arid southern New Mexico campus.
"Hands down, it was the winner," Leinauer said. "Over a year's time, this system used 50 percent less water than our traditional sprinkler system. On top of that, during the hottest part of the summer, it used about 80 percent less water."
Two years ago Leinauer and his colleagues built what they call a rolling green, a 41,000-square-foot series of subsurface drip and sprinkler irrigated plots. One of the turf trial's critical elements is its alternating series of south-facing 5 percent slopes followed by flat areas.
The project is funded by NMSU's Experiment Station, the U.S. Golf Association, Toro Co., and the Rio Grande Basin Initiative.
"The information from these sloping areas is very important because not all turf areas are flat," Leinauer said. "We're trying to match real-world conditions such as you would find on a golf course or in your own yard."
Creeping bentgrass, used on many of the state's golf greens, was selected for the experiment because it is one of the most intensively maintained grasses in New Mexico. From a bird's eye view, Leinauer's rolling green looks like a huge, manicured or well-maintained golf green.
But underneath the green carpet is a complex array of irrigation systems, including traditional pop-up sprinklers, subsurface drip irrigation and subground irrigation.
Sprinklers, which apply water to the surface, are commonly used in many parts of the state. In subsurface drip irrigation, water is applied directly to plant roots through a grid of black plastic lines or drip tape buried more than a foot deep.
Subground irrigation uses a combination of flood irrigation and 5-by-5 foot drain tiles or trays. The three-inch-deep tiles are buried a foot below the surface, and water is injected through a patented distribution system at very low pressure into the trays. The water then wicks to the surface from the base of the trays. Installation is about double the cost of a conventional sprinkler system.
Evaporative Control Systems, invented by Jonas Sipaila in Reno, Nev., are specifically targeted for newly constructed golf and housing developments. "This isn't something that can be easily retrofitted," Leinauer said. "You really have to start from scratch."
Because of the cost and scope of installing subground irrigation, Leinauer doesn't foresee its application over entire golf courses. But the method could be applied to high-profile areas like greens and specific fairways.
Leinauer admitted that subground irrigation is "a little far out there, but part of our job is to look at where we can be." With the population continuing to grow in the Southwest, water conservation will remain a high priority for the foreseeable future, he said.
Scientists know that more than 90 percent of the water used by grass goes to transpirational cooling. In other words, the water evaporates from the leaves to keep the plant cool.
Leinauer's rolling green experiment is scheduled to run at least another 10 years to determine the long-term viability of irrigation systems. "Root intrusion and plugging are always a concern," he said. "The performance of the systems needs to be monitored."
© 2013 New Mexico State University Board of Regents
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