To core or not to core? Washington course stops pulling cores

Core aerification is a vital practice at many courses. But for some cool-season grass courses, it’s a thing of the past.

The sewer ditch was 5 feet deep, 30 feet wide and a mile long. It cut a path of destruction — a big, gaping hole — right through the heart of 120-year-old Tacoma Country & Golf Club in Lakewood, Wash.

It was the spring of 2010. Superintendent Joel Kachmarek looked at the long list of projects necessary to repair the damage the city caused when it dug the sewer trench on the property. He decided core aerification would have to wait — he just didn’t have the manpower.

He decided to topdress, solid-tine aerify and hold off on core aerification until later.

That September the club faced a serious rain event that would have turned any pulled cores into a muddy mess. Instead, Kachmarek topdressed and solid-tine aerified again.

The following spring, clean-up from an ice storm made core aerifying impossible, so the crew topdressed and solid-tine aerified the fairways and greens once more.

It’s been five years now, and Kachmarek is yet to pull a core on his golf course.

“As we did three applications of solid tining on the fairways and were not seeing a negative from that, we just kept it going,” Kachmarek says, “and we’re still waiting to see if there’s a time when we think they’re not draining well, or they’re soft and we should core. But we haven’t had that feeling yet. Actually, it’s quite the opposite. We have felt that the fairways have been firmer than ever and draining just fine.”

He says the greens and fairways have been topdressed for so many years that “they’re straight sand, 8-inches deep.” Rather than pulling cores, he aerifies using solid tines twice a year in the growing season, combining that with heavy topdressing. He also bought a VertiDrain deep-tine aerator that he uses twice a year to further improve drainage on the property.

30 years, no cores

It might seem that Kachmarek is bucking conventional wisdom by not pulling cores. But research shows that he may be onto something. And he’s not alone.

CAN YOU CUT OUT THE CORE?

Back in 1978, shortly after Kurth Thuemmel, CGCS, became superintendent at Walnut Hills CC in East Lansing, Mich., he read about research by William B. Davis conducted at the University of California, Davis, titled “Pros & Cons of Frequent Sand Top Dressing.” That research affected how Thuemmel managed the sandy loam greens at Walnut Hills for the next 35 years.

For the first two years, Thuemmel instituted a program of heavy topdressing, complemented by core aerification. At the end of those two years he believed he had built up a sufficient profile of sand on his greens. He stopped pulling cores completely.

For two decades, he topdressed every three weeks. In the last 15 years of his tenure at Walnut Hills, he topdressed every two weeks at a lower rate because by that time mowing technology had improved, allowing mowing heights to come down. Cutting the grass shorter meant the bedknives were lower, too. Switching to every two weeks at a lighter rate kept the mowers from getting bogged down and dulled by the sand.

From time to time, he’d solid-tine aerate, “if a localized problem” arose. Thuemmel now jokes that his colleagues called him the “crazy old guy at Walnut Hills” for not core aerifying. However, “I really didn’t go out on a limb,” he says, “because I followed the guidelines that those researchers in California had put out.”

Thuemmel retired in early 2014. The new superintendent at Walnut Hills, Kurt Grost, CGCS, had been Thuemmel’s assistant superintendent for 16 years. He’s kept Thuemmel’s philosophy going.

“We have no standard aerification schedule on the greens,” Grost says. “As needed, greens are solid tined, star tined in season for venting purposes, no more than one time per green during the growing season. I am considering one deep-tine aerification next year with solid tines for increased rooting, venting to get a little deeper in the profile than our standard 3- or 4-inch.”

After 35 years of consistent topdressing, the greens at Walnut Hills are transformed. Want evidence? Cut a cup on those greens and look at the profile.

“We’ve got sand built up — over what was originally push-up greens — in many places up to a foot deep,” Grost says.

What the research says

Roch Gaussoin, Ph.D., extension turfgrass specialist at the University of Nebraska-Lincoln, published research on the benefits of topdressing and solid-tine aerification versus core aerification. His premise began with a historical perspective.

“When we were building greens out of locally available materials and didn’t have aeration,” he says, “we would have compaction. Then we started pulling cores and putting sand topdress on greens.”

Although times and technology changed, core aerification didn’t go away. Gaussoin wondered why that was, when newer construction methods and designs (such as USGA, Hurdzan and California-style greens) were developed that incorporate sand into the soil profile.

“Sands don’t compact readily. Is there still a reason to pull the core? It’s labor intensive and disturbs members. I decided to venture out,” Gaussoin says.

In his research, Gaussoin discovered that the “golf courses that were topdressing a minimum of 20 cubic feet per 1,000 square feet per year had the best quality greens and were doing less aggressive aerification than coring.”

The caveat to this was that Gaussoin’s research was limited to courses grassed with cool-season turf on their greens.

“(In) my conversations with colleagues in the South and Southwest, where they have bermudagrass or pasplaum, they said they wouldn’t try it,” he notes. “Warm-season varieties are aggressive grasses with a longer growing season. This is only for cool-season grasses — bentgrass or Poa/bent combinations. That’s where it’s been tested. Especially ultradwarf bermudagrasses that have a heavy root production, they may require physical removal,” Gaussoin says.

Wayne Rath, CGCS, is the superintendent and property manager at Magna GC in Aurora, Ontario, Canada. He first met Gaussoin in 2000 when Seed Research of Oregon named Magna’s greens the best 18 greens in North America. He thought of Gaussoin again three years ago when he needed a bit of guidance.

“Three years ago was the summer from hell. We ran into some trouble. We had a little too much fertility on the greens, a little too much organic matter. We were living the fat life a little too long on greens,” Rath says.

He did some Internet research, and what kept coming up was Gaussoin’s PowerPoint presentation, “Dilution is the Solution,” a program that touts heavy topdressing and solid-tine aerification to dilute with sand the organic matter in the greens profile. He asked Gaussoin to visit his course.

“As soon as he left, we did a full half-inch tine with heavy sand,” Rath says. “We bought into his program, modified it a little bit, but keep in mind the foundation with sand and solid-tine aerification. What Roch brought to our operation was not to be afraid to solid tine. We still will pull a core a little bit, but dilution is the primary foundation of what we do. We bought into the concept that sand is our friend.”

Both Rath and Kachmarek agree that the key to the sand application is to topdress first, then punch solid tine, and drag in any remaining sand.

Could core aerification become a thing of the past on courses with bentgrass or Poa greens? Grost says he’s a believer.

“It’s not a perfect system and it’s not for everybody, and it’s actually quite contrary to what 99 percent of the people in the business would tell you,” Grost says. “But it works.”