Combating compaction

Heavy traffic on greens causes turfgrass stress that includes turfgrass wear and soil compaction. The No. 1 problem experienced on sand-based putting greens is the excessive accumulation of organic matter in the upper portion of the soil profile, according to University of Georgia researcher Bob Carrow. Compaction is a hidden issue because it affects the soil underneath the surface, altering its physical properties in a manner detrimental to turfgrass growth.
Aside from limiting traffic on greens, core aeration and sand topdressing are the two most effective means to control the content and distribution of organic matter in the upper zone. Several courses have modified traditional programs to achieve the conditions they want.

A change in strategy
One of the courses is Whistling Straits in Kohler, Wis. The staff there started to prepare for the 2004 PGA Championship several years ago because it had to.

Tom Huesgen has the Pebble Beach course aerated with different-sized tines.

“Our cultural practices haven’t changed much in the last few years,” says Michael Lee, manager of golf. “The time to experiment is five years before the event, so we have time to get it right. We’ve been doing things a certain way for a couple of years, and it’s been working. The last thing we want to do to prepare for a major championship is to change our programs at the last minute.”
One of those practices, which has been slightly modified, is greens aeration, which has more than one purpose.
“Sometimes we aerate to relieve compaction, but for our sand-based greens, the goal is to remove soft, water-holding thatch,” Lee says.
Standard quad-tine holders on aerators are modified to accept ½-inch tines instead of ¼-inch tines. This changes the hole pattern from 2 inches by 2 inches to 1 inch by 1 inch. A larger hole and tighter spacing allow more material to be removed per pass. Whistling Straits superintendent David Swift estimates that about 10 percent of the thatch is removed with each aeration.
“Our program for greens is twice as aggressive in spring,” Swift says. “As soon as we finish 18 holes, we topdress, turn around and do the greens again. We’re removing about 20 percent of the thatch. We do this early enough in the year (early April) when we don’t have any guest play. The greens will be 80 to 90 percent healed by the time we open later in the month. It’s important to understand that greens that are double aerated heal in the same time period as single aeration. The distance the grass has to grow over the holes is the same for single or double aeration.”
After aerating, the cores are blown from the edge of the green to the center. Staff members push them into windrows using shovels, and then they are scooped up and loaded into utility carts.
“There are a number of ways to do it that might save more time, but we’ve found the best way is with people and shovels,” Swift says. “This eliminates as much mechanical damage as possible and gives us the best quality.”
The greens aeration is repeated in late summer or early fall, except that the machines make only one pass.
But this formula wasn’t always in place. The formula took a few years to develop. In 2001, greens aeration was done in play, six greens at a time. The program was modified slightly in 2002 and last year was fine-tuned to the current system.
“We had great success aerating early in the year in 2002, so last year we double punched because the greens healed up so well,” Swift says. “Trying to aerate in play is a drawn out, frustrating process for golfers and the staff. This program works best for everyone.”
Swift credits the speedy spring healing to fertilizing in late fall.
“We call it our dormant feed,” he says. “The plants are charged up and ready to grow right away in spring. We fertilize after we spray for snow mold and then give the greens a pretty good topdressing. This also protects them from winter desiccation because we get a lot of wind on the Straits courses. The greens came through in excellent shape this year.”
And during summer, the greens are verticut at two-week intervals, sometimes weekly if the grass is growing aggressively. They also are topdressed lightly once a week with dry sand.

Fairway aeration
When a resort course shuts down even for one day to aerate, the revenue loss can be significant. Management used to set aeration dates at the four courses that make up Blackwolf Run and Whistling Straits  one year in advance and close each course for two days. This was always a gamble because of weather.
“Until six years ago, we used to do the conventional method of core aeration,” Lee says. “We’d pull the plugs, leave them on the course and hope they’d dry. If we tried to break them up when it was wet, the fairways became mud slicks. If it was too dry, the cores hardened into little rocks. We’d have to aerate at just the right time, and that didn’t always happen.”

Fairways are aerated each spring, and plugs are removed with core harvesters. Some material that’s still on the surface is dragged in with a keystone mat. Then blowers remove any remaining thatch.
Then the plugs are hauled to a building where they dry out during the summer. In the fall, a soil shredder pulverizes them, and the dust is put back onto the fairway. A major benefit of this aeration method is that the soil is incorporated into the thatch.
“The soil contains microbes, which break down the thatch,” Lee says. “So we want to incorporate this soil below the thatch layer. Over a period of years, we just keep turning the soil over so as not to end up with a strong thatch layer on top.”

Blackwolf Run staff members push aeration cores with shovels into windrows, then the cores are scooped up and loaded into utility carts.

Ron Bierwirth, superintendent at Blackwolf Run, says this aeration method is much cleaner, too.
“Golf cars can drive on the surface right away, and golfers barely notice what we’ve done,” Bierwirth says. “With the old method of trying to break up the plugs and drag them back in, the course would be disrupted for a week or two – longer if it rained. Although aerating fairways the way we do it now can take a month or more, at least we can pick the dates to get the best possible weather conditions. The most important benefit is that we don’t have to close the course.”
“We have a saying at the Kohler Co. that could apply to the way we approach our cultural practices: ‘Doing the common in an uncommon way,’” Lee adds.

Daunting challenges
Across the country, preparing Pebble Beach Golf Links in Monterey, Calif., presents a set of challenges not found at many resort or tournament courses. Consider what superintendent Tom Huesgen deals with daily:
• The course is open 365 days a year and posts 65,000 to 70,000 rounds;
• The greens are the smallest of any professional tour venue, averaging 3,300 square feet;
• Annually, there are more than 40 significant tournaments and large corporate events, three professional tournaments and the California State Amateur – Pebble Beach again will host the U.S. Open in 2010;
• Monterey Peninsula has dramatic climatic changes, and within the golf course there are several microclimates; and
• Water quality is poor, and the influence of the ocean presents additional sodium difficulties.

Tom McCarthy, superintendent at Inglewood Golf Clob in Kenmore, Wash., used three-quarter-inch tines when he aerated this past fall.

Still, Pebble Beach remains one of the best-maintained golf courses anywhere. How does Huesgen do it?
“One of the ways we deal with our heavy traffic is to alleviate stress on the greens,” he says. “Last year we recorded 10 aerations. We do a big aeration twice a year using 5/8-inch tines, sweeping sand into the holes and across the surface. This is done in late March and late September. In between and during winter, we aerate with ¼-inch tines. Sometimes we pull cores, but not always. At other times, we go out with solid tines.
“We have no choice but to open up the greens regularly and allow gas exchange to take place,” he adds. “This also allows potable water that we get once a month for five days to infiltrate the soil and help flush the sodium.”
Also, every two weeks greens are verticut and topdressed. During the peak growing season from April to October, verticutters are used in between that period at a height approaching that of turf groomers.
“It just depends on stress levels and what events are coming up,” Huesgen says. “The sand gives us a firm, ready surface and combats compaction.”

Selling an aeration program
At Inglewood Golf Club in Kenmore, Wash., Tom McCarthy, director of golf course operations, tried something new this fall when he aerated the greens. McCarthy used ¾-inch tines.
“That’s huge for us,” he says. “We have a lot of play in the summer and mow our greens at 0.1 of an inch. With the summer heat and stress from play, we try to keep the greens pretty firm. But by September the wear and tear starts to show. This aeration opens up the greens to get more air in the root zone. Bigger holes give us a good infiltration rate, so when it rains the water goes through the soil profile.”
The front and back nine at Inglewood each are closed for one day to complete the process. Recovery time can be three to four weeks.
“Not many superintendents do this because of golfer complaints, but I told the club this is what we have to do to get the conditions they want,” McCarthy says. “It’s one of those trade-offs. I’m not necessarily thinking about today when we aerate. Instead, I’m looking ahead to get through the winter and have a good start in spring. If golfers want to enjoy the course year-round they have to take their medicine. Cultural practices are just as important as fertility programs. They’re the foundation of a well-conditioned course.”

Aerate twice a year
Greens aeration at Inglewood is scheduled for April 15 and Sept. 15, weather permitting.
“I don’t want to spread it out too far,” McCarthy says. “Sometimes the golf calendar pushes it earlier in spring and later in fall, but then the fall recovery isn’t as good, and fall really sets us up for spring. In the Northwest, we get a lot of rain, so when we aerate and get sand back in the holes there is good infiltration rates. The surfaces stay relatively dry and firm. This equates to healthy turf and reduced disease pressure so we don’t have to use as many chemicals.”

At Whistling Straights in Kohler, Wis., greens are aerated twice and heal just as quickly as greens that are aerated once, according to superintendent David Swift.

McCarthy doesn’t fertilize heavily. Ten days to one week before aeration, the staff puts down ¾ of a pound of nitrogen per 1,000 square feet.
“This gets the greens growing so when we aerate they recover more quickly,” he says.
Next comes sand and calcium for the root zone. Ten days after aeration, the staff applies another ¾ of a pound of nitrogen.
“We want to regenerate the Poa annua leaf tissue because fall is a perfect time for growing grass here,” McCarthy says. “There is high light intensity during the day and cool evenings for optimum soil temperature. If we get too far into the fall, soil temperatures drop, and light intensity decreases. That’s why I insist on these dates.” GCN

David Wolff is a freelance writer based in Watertown, Wis. He can be reached at dgwolff@charter.net.