Things have sure come a long way since the early days of golf, when – once irrigation was introduced – courses would typically employ a night waterman to make the rounds (perhaps with flask in hand) to make sure that enough water was flowing out of the pipes to keep the greens from turning brown.
Water management on putting surfaces is a bit more advanced these days, especially for those in southern climates who manage warm-season turfgrass – if for no other reason than the large number of species involved.
Dr. David Kopec, a specialist in the school of plant sciences at the University of Arizona, estimates that 95 percent of all warm-season turfgrass golf greens are bermudagrass.
“Maybe 5 percent are made up of alternative species of seashore Paspalum and zoysiagrass,” he says.
Kopec estimates that 60 percent to 65 percent of those bermudagrass putting surfaces are ultradwarf varieties released within the last 20 years. The remainder are the “old fashioned” bermudagrasses, such as TifGreen and TifDwarf, which are still being used. Understanding the differences in water management is important, especially for superintendents who work at courses where older greens are being renovated with newer ultradwarf varieties.
“Depending on the root zone, and all other things being equal, the ultradwarfs don’t have as deep of a root system as the older bermudagrasses, and they’re slower to recover if they become excessively droughted,” Kopec says. “The bottom line is that the ultradwarf bermudagrasses can’t go as many days after a heavy watering as the older bermudas, so you have to keep an eye on that. The older bermudagrasses can go a longer period of time because they have a deeper root system, so there’s a deeper volume of water to draw from.”
In other words, it’s not that the overall water use is dramatically different – it’s the amount of time between waterings after a heavy (flood) irrigation cycle, Kopec says.
“In general, at least here in the Southeast, the most popular method is to replace the water that the plant uses on a daily basis,” says Patrick O’Brien, an agronomist in the USGA Green Section’s Southeast Region. That’s especially true on courses with ultradwarf bermudagrass greens, he says. Most superintendents determine how much water that is based on weather station data about the evapotranspiration (ET) rate each day.
“The National Weather Service also has a site that included predicted ET for a week in advance, so superintendents can at least see what the trends are,” he adds.
For bentgrass greens, superintendents in the Southeast typically replace about 80 percent of the ET value; on bermudagrass greens, the figure is usually 70 percent. That can be handled during a nighttime irrigation cycle.
The next morning, many superintendents will use a moisture meter, outfitted with a 1.5- or 3-inch probe, to check the greens. “They want to know what volumetric water content, based on their root zone conditions, that they need to fill the upper profile to in order to get them through that day,” he explains. “Superintendents know, through soil conditions and experience, what level to fill that up to, whether it’s 20 percent or 25 percent or whatever.”
The goal, O’Brien says, is to get that percentage dialed in by hand-watering any areas that need it in the morning so there isn’t any need to go back out in the afternoon to touch things up.
“Superintendents are so good now at dialing in their greens – plus the irrigation companies, with the sprinklers that we have around the greens – things have just gotten so precise when it comes to putting moisture into a green,” O’Brien says.
For the golfer, that means consistent putting conditions, day after day.
O’Brien says that while Agronomy 101 might recommend thorough, infrequent watering to encourage the deepest root growth, he doesn’t necessarily believe it. “I just have never seen a real impact from daily watering on the root system,” he says. “I don’t think we’re doing anything agronomically that’s setting the plant health back.” He also points out that ultradwarf bermudagrasses have fairly short root systems, anyway.
Dr. Jay McCurdy, assistant extension professor of turfgrass science at Mississippi State University, says precision-sensing the amount of water on greens “has been the biggest revolution, as far as adjusting the amount that’s being put down through irrigation.”
He adds that the term “precision,” at least in agricultural irrigation circles, implies the development of a map and a method to apply water with great accuracy.
“That’s not what we have on golf course putting greens, but using tools like the POGO or the TDR probes from FieldScout (Spectrum Technologies), just as examples … I think we’re heading toward those same abilities, at least on a smaller scale,” he says.
McCurdy and other researchers have done some early, as-yet-unpublished work using FLIR thermal imaging cameras to detect moisture levels on greens. Irrigation may not yet be as exacting as high-tech precision agriculture systems, but the gap is closing.
That’s where the expertise of superintendents pays dividends. “They are able to take those tools and develop their own local knowledge and intuition” to best use the information that the tools provide, he says.
Starting with random samples, a superintendent might try to develop an average for a particular green. Over time, he might notice that the health of the green begins to suffer when it gets below a certain percentage of volumetric water content.
“Every tool can differ, depending on the salt index and water quality, among other things,” McCurdy says, adding that improvement depends largely on the intuition of the superintendent.
Consistency in important when sampling soil moisture on greens – and that doesn’t just mean consistency in the location of samples and tool use, McCurdy says. “It’s consistency in the person who’s using the tool, because there can be a lot of sampling error,” he explains.
The benefit of all this precision is that the level of subjectivity has been reduced, O’Brien says. In the old days, a course employee might be sent out to take soil plugs and come back to report that the back of the eighth green was dry, and the front of the seventh green was wet. The terms “wet” and “dry” are open to interpretation, and like speaking two different languages, can cause confusion.
On the other hand, if the report is that the moisture level is 24 percent – and there’s consistency in the equipment and method used to obtain that figure – then there is some solid data to work with.
“There isn’t any question at all: Everyone is speaking the same language,” O’Brien says.
Even many lower-budget courses now have moisture meters. “Everyone has caught on about how to do it,” he says. “One moisture meter costs about $1,000, and it’s worth every penny.”
Good Product Placement
On TifGreen (or 328 bermudagrass) putting surfaces, it was once common for superintendents to control the growth of the grass with water, Kopec says.
“On the ultradwarf varieties, growth today is controlled almost exclusively by plant growth regulators,” he explains. “They don’t fiddle very much with the irrigation to do so.” On the old fashioned TifGreen, he notes, plant growth regulators are typically used to make the grass tighter and shorter for a better rolling surface, but not necessarily to control the growth.
Plant growth regulators aren’t the only products being used for water management on greens. “I think another way that we’re heading is the increased use of soil surfactants, or wetting agents” to control moisture levels in greens, McCurdy says. The practice has revolutionized water management over the past 15 years or so, and that is expected to continue.
“I think a majority of wetting agents are used to retain water, as well as to reduce water inputs,” McCurdy explains, adding that some wetting agents are actually penetrants that will move water through the soil profile.
As a result, supers need to be sure they’re using an appropriate wetting agent for what they’re trying to accomplish – moisture retention versus moisture removal. “A lack of water, as well as too much water, can be equally damaging to greens,” he points out.
Of course, mechanical products also have a role to play. “Application technology is changing,” McCurdy says, citing advancements in irrigation-head technology as an example. “Being able to have soil sensors built into a green that can sense moisture – or above-ground technology that can catch and monitor rainfall or humidity – are tools that help us monitor inputs and losses, and more efficiently manage water.”
Again, the emphasis is on ever-increasing precision.
Kopec does caution, however, that new irrigation components do not necessarily ensure more precise water management. “There are still a lot of courses that have full-circle heads that cover the surround and the green at the same time,” he says. “So if the surround gets dry, they turn it on and then the green gets wet.”
A dual system, on the other hand, provides better control over how much water the green gets. “But you’d be surprised how many new courses get built without them,” he says.
Water quality is another issue that needs to be examined when irrigating greens, or any turf for that matter. You can’t just look at the water source to determine quality.
“People think that just because water is reclaimed, it’s going to be salty and horrible, and just because water is potable, it’s got to be good,” Kopec says. “Well, drinking water can more salty than effluent water.”
The point is that irrigation water needs to be tested.
When it comes to managing water on greens, the more data, the better. It’s all about precision. “That’s the way we do it on golf courses now,” O’Brien says. “There ain’t no guessing going on!”