Common characteristics between subsurface drip irrigation (SDI) and hydronic systems include more flexible maintenance routines, environmental benefits, cost efficiencies and an untapped potential.
In 2019, Southern Hills Country Club in Tulsa, Oklahoma, reopened after a major renovation with a hydronic system installed under 25 surfaces, including course greens, the putting green and the nursery green. “It’s a game changer,” Southern Hills superintendent Russ Myers says. The Club at Las Campanas in Santa Fe, New Mexico, is using SDI for bunkers, tees and on some edges of fairways and roughs.
“Courses are often familiar with using SDI on bunker faces but installing this technology in teeing grounds is a new concept,” says USGA Green Section West Region agronomist Brian Whitlark. “I don’t think cost is a problem as SDI is not really more expensive than PVC overhead irrigation, but the SDI can’t be seen while it’s working and that makes people uncomfortable. We are seeing a 50 to 80 percent reduction in water use with drip compared to overhead irrigation.”
In 2016, Dr. Bernd Leinauer, regents professor and turfgrass extension specialist at New Mexico State University, received a grant from the USGA to learn more.
Subsurface Drip Irrigation
Leinauer worked with Tom Egelhoff, director of agronomy, and his team at Las Campanas. The Sunrise and Sunset courses, both 18-hole Jack Nicklaus Signature designs, have bentgrass tees, greens and fairways. The rough is bluegrass and there are five teeing grounds on each of the 36 holes. The research started with six tees and testing materials donated by Toro and Rain Bird. Two years later, Netafim and Hunter joined the research. The four product lines are currently being tested on three tees each.
SDI requires placing drip lines four to six inches beneath the surface to supply water directly to the root zone through emitters, ideally spaced 12 inches apart. The flow rate is between a half-gallon and two gallons per hour and most emitters are pressure-compensating. The overarching benefit is water conservation as SDI provides a reduction in the amount of water needed to supply an area of turf. Las Campanas is consistently seeing a 50 percent reduction in water use for areas utilizing SDI and it could be more. The evapotranspiration rate helps determine how much water is needed and run times can be set manually or automated. For optimal efficiency, run times and the ET rate should be calculated and adhered to weekly.
SDI makes irrigation more flexible because the watering window is extended. The course can be watered as people play or when off-peak water rates are available. “We normally water the tees at 6 a.m,” Egelhoff says. “They aren’t running at night with everything else.”
Normal maintenance takes place on SDI areas. “Our first few years having SDI we would verticut those tees aggressively instead of aerating them. Now, we pull shallow plugs on the tees in spring or fall,” Egelhoff says. Regarding maintaining the SDI system, “periodically, check the Y-strainer before the valve. That’s a little bit extra but it’s not cumbersome,” he adds.
It’s clear if something is wrong. “Clogged emitters create round areas of dying or stressed grass and there you dig,” Leinauer says. “Emitter clogging is a concern with very hard water but with a sulfuric acid injection it can be overcome.”
SDI also prevents wind drift, spray overlap and overspray, particularly useful in the desert. Eliminating overspray saves labor hours managing unwanted plants, and on island tees, SDI creates defined contrast along the edges. Water is not lost through evaporation and a lower operating pressure can be used to save energy. With carefully controlled moisture levels, disease pressure can be reduced.Drawbacks for drip irrigation include the upfront cost, disruption for installation, no deep-tining and difficulties determining setup. Granular applications require consideration, though they can be hand watered or washed in by the rain (tricky!) or use overhead irrigation. It is possible to deliver liquid fertilizer through the SDI system. Longevity of the systems is unproven, but SDI systems should be as durable as standard irrigation systems.
Another advantage to SDI is that it makes it easier to use effluent water. By law, many courses using effluent water must keep sprinkler heads a certain distance away from residential or commercial boundaries. With SDI, that is more manageable. “The fairways are close to some external properties at Las Campanas so using SDI in some fairway and rough areas eliminates the risk of wind drift or overspray,” Leinauer says.
Mowing is unaffected. “If anything, you don’t have to worry about sprinkler heads being damaged when they stay up after sprinkling. SDI, overall, has lower maintenance than overhead sprinklers,” Leinauer says. And when SDI is used near bunkers, there is no water washing out the sand.
Costs of systems vary a great deal and depend on soil type, product type and amounts of hardware required. Costs are offset by relative water rates, maintenance benefits, changes in labor and playability. Honestly, there’s a lot to think about but while you’re at it, another ground-breaking technology (terrible pun?), is hydronic systems.
A hydronic system is a closed loop roughly 12 inches below the surface that can circulate warm or cool water to alter the temperature of the soil. It operates in the same way that a heating/cooling system does for a house, but instead of circulating air, liquid is circulating (water, gaseous water or a water-solution).
At Southern Hills, a few people on the staff know how to work the system and it’s not complicated. “There are set points and we monitor that it’s operating properly,” Myers says. “With our system, we know that five inches down we are 15 degrees cooler on the greens that have it.”
The hydronic system has shifted labor requirements. To keep the bentgrass greens cool during summer, hand-watering them requires four skilled staff members watering from 5 a.m. to 5 p.m. for about 12 weeks. “You are locking those people in to that task every day and it’s a huge commitment,” Myers says. That affects water use and playability. “Now, over those 12 weeks you might have 15 to 20 days where you hand water spots and you might send one person around in the afternoon to help dry spots on greens,” Myers says. The need for fans (previously two per green) has been eliminated and those are significant changes.
Myers is effectively managing turf in a more controlled environment. When it’s too hot, the grass is challenged by a temperature where it won’t photosynthesize properly. “It’s not able to handle stresses and traffic, won’t recover from ball marks and struggles with 90 days of rolling and mowing in the heat,” Myers says. Reducing temperature stress enables Southern Hills to mow six days a week and maintain consistent green speeds year-round. “We lose a little bit of firmness but not as much as we would without the hydronics,” Myers says. The risk of having to close the course due to heat making areas unplayable is also almost eliminated.
Another benefit of hydronics is a more flexible schedule for aerating. Courses normally aerify as close to the oncoming heat as they can, usually May. Southern Hills doesn’t have to, translating to an additional four weeks of premium playing conditions. Aerification happens when it needs to be done instead of on a rigid schedule, so maintenance practices affect golfers as little as possible. October aerification can be pushed into November by using hydronic heating, to help the grass grow and recover from aerification. Myers can also verticut throughout the year, when normally that would be too risky in the summer. “I am a lot more comfortable executing maintenance practices in stressful environments than I would be without the temperature control,” Myers says.
The Southern Hills system was sold through Precision Small Engine out of Pompano, Florida. The units are built by RAE Technical Systems. There are components that may need to be replaced occasionally but the system should last around 30 years. The hydronics system works even more efficiently than expected, so scalability is something to consider.
“The more it is in use, the more that can be learned about what is optimal for each site and location,” Myers says. “When I worked with hydronics at Augusta National Golf Club and Los Angeles Country Club, and as I speak to other superintendents, it’s hard for people to understand. I couldn’t be a bigger believer in this technology.
“To install it, the greens need to be rebuilt and the environment needs to make sense,” he adds. “It’s in its infancy but don’t miss the opportunity to put the infrastructure in. You have electrical costs and expenses but as far as what you are providing, in certain places, if you don’t do it when you next renovate, by the time you renovate again, everyone around you is going to have it, making it hard for your property to compete.”
The members at Southern Hills are willing to invest in the playing experience and the membership at Las Campanas is supportive of sustainable development, with both clubs utilizing available technologies to achieve their goals. “In our industry we should be taking more time to explore,” Egelhoff says. “If no one takes a chance on the technology and it doesn’t have the support it needs going forward, we can’t get better.”
The work of SDI and hydronic systems is imperceptible to many, but for course maintenance, the potential is easy to see.