Features Agronomy
Achieving greens that perform high

Achieving high-performance putting greens doesn’t just mean fast and firm, but how well they cope with traffic, an associate professor of turfgrass science at Cornell University said in January at the Ontario Golf Management Conference in Niagara Falls.

Dr. Frank Rossi, who is also New York state extension turfgrass specialist, said golf course greens must be resilient and keep up with varying climates. Superintendents should be able to “play defence” on them and not have to aggressively push them, yet can “play offense” on them as well for such high-end events as member-guest days.

“I don’t want you to think that high performance simply means fast greens,” he said. “I think that if you are doing 35,000, 45,000 or 50,000 rounds a year – if it’s a high traffic rate – you may have greens that are not necessarily faster than nine or 10 feet on the stimpmeter, however, they hold up to the wear and tear really well.”

Rossi said, to him, high performance is having a lot of flexibility to what can be done with putting surfaces. Firm, he said, has trumped speed “because we know that if they’re firm they’re likely to be fast.”

By focusing on firm, speed will likely be the result, he said.

Much of that has to do with how well firm greens hold up under mowers and the way mowers are set up to allow high performance on the surface. Not only must greens be firm, they must be able to breathe.

“If they’re not breathing and they get wet, they’re going to be dead.”

To ensure they don’t stay wet, Rossi said they need “holes” in order to drain, but he warned an excessive number promotes a counter effect.

“You can’t have it all like Swiss cheese because you won’t be able to get them firm.”

It is difficult to get sand into the profile in a manner that allows for widely graded sand that is more likely to firm up. He said one of the challenges of the United States Golf Association system is that if the right sand isn’t used, it will be more difficult to achieve firm greens.

Rossi said if greens aren’t put under stress levels purposely created by superintendents wishing to achieve higher performance surfaces, sometimes failure occurs. He emphasized the need for stress tolerant plants, knowing that they’ll hold up better.

When greens are managed for high performance, the plants are being stressed. Mow tighter and the surface becomes denser. Verticutting greens promotes density, allowing them to be mowed lower. Boosting traffic, including rolling, helps to manage organic matter.

“They don’t get as thatchy if you’re wearing on them a little bit all the time.”

Mowing activates plant defences, he said, while rolling and a little bit of stress likely activate some plant defences that help in other ways.

Potassium levels
Regulating potassium levels is important when favouring bentgrass over annual bluegrass or vice versa.

“The less potassium you put on, generally the less annual bluegrass you could potentially have. We know that one needs more than the other.”

Rossi said he wouldn’t recommend the use of potassium at all if annual bluegrass putting surfaces are desired.

If greens have chronic areas that fail no matter what is sprayed on them, it is important to see what wants to grow there, he said, suggesting seed be put down to see how re-grassing goes. It can’t be done unless deliberate stress is imposed, he added.

Basal rot anthracnose won’t infect actively growing plants, he said.

“It’s a very weak pathogen by definition.”

Because it’s so weak, the pathogen will only be successful when the plant is in a weakened condition that is the result of the cultural conditions imposed upon it.

Rossi said mowing, topdressing and applying nitrogen are perhaps the three most important factors that can collectively achieve the desired green speed without creating too much stress. Topdressing must continue during stressful times, especially if anthracnose is present, because some distance needs to be created between the plant’s crown and the mower.

“Topdressing is probably the single most important cultural practice that you have to maintain throughout the growing season for high performance putting surfaces.”

Annual bluegrass becomes more susceptible to basal rot anthracnose when it is deficient in potassium, he said, adding if levels get below two per cent, higher levels of anthracnose are likely to be realized.

“Applying regular potassium in ratios that make sense with your nitrogen is pretty much what we would tell you for good annual bluegrass management, depending on how much growth you’re getting.”

Nitrogen is important for achieving high performance surfaces, he said.

“I would be really careful about striving to drive your nitrogen rate down unless you feel it’s excessive.”

Golf courses that don’t have a rolling program won’t realize greens that are as firm as they should be, Rossi said.

“The key to a rolling program is that you have a program and that you do it consistently.”

Research shows that the cumulative effect of rolling is the benefit. But Rossi said he is becoming suspicious about good topdressing practices coupled with the increased amount of stress emanating from the amount of rolling being done, noting collar dams are beginning to develop. Rolling quickly in the same direction and then slowing down once getting to the green’s edge can create a shift in the sand, forming tire tracks that can produce collar dams.

Still, he said, rolling must be done if firm greens are the goal.

Breaking up the surface?
Fifteen years ago, aerating greens during the growing season was rarely practised, but it’s a common procedure today that helps to firm up putting surfaces. Breaking up the surface to get air in and out is vital.

“If they’re breathing and you’re topdressing them and you’re rolling them, they’re likely to get firm.”

Those practices must be balanced with nutrition and growth regulation, Rossi added.

Research suggests that given the choice of topdressing with fine sand or not topdressing at all, use fine sand. He said about 40 cubic feet of sand per 1,000 square feet a year is what the research recommends, but there are no absolutes and the numbers might have to be tweaked.

“Frequency matters. You don’t want to go long periods of time with significant amounts of organic matter accumulation and then put a bunch of sand on it.”

If the profile isn’t kept uniform, firm greens won’t be achieved. Water management also plays a role.

Using nitrogen to keep up with traffic and to deal with pest issues results in a lot of low ground growth when finer sands are used, and an abundance of organic matter will result in dense and firmed up greens, Rossi said. Superintendents must therefore be diligent with keeping their greens porous. He cited the Dryject machine as an ideal means to blast sand down and create channels with little surface disruption. The method allows for enormous amounts of sand to enter the soil profile by breaking through layers. It’s a way to incorporate larger particle sizes such as two or three millimetres to help with uniformity and help firm up the system.

Fast and firm greens are more likely to be true, he said.

One of the most critical aspects of mower setup is the bedknife position, which is relative to sand and firmness.

“It’s still something we’re not considering as much as we should.”

The further back the bedknife attitude is set from behind the centre line, the more the reel dips into the canopy. The geometry of the entire mower unit is altered because of the bedknife position.

If sand is put down to firm the green and the mower’s bedknife is positioned back of centre, not only will the canopy be thinned out, sand will be picked up. Rossi said that’s the time to adjust the mower setup “and not sacrifice the mower as a sand mower.”

It’s one way of dealing with a uniformity problem that might exist with some sands, he added.

Superintendents must be aware of plant growth and collect the appropriate data, including the amount of clippings generated, “not because it’s going to tell you how fast or slow your greens are, but because you need to determine sand rates, PGR (plant growth regulator) rates, nitrogen rates, how they’re holding up to traffic, and maybe disease.”

Studies show growth regulator applications on collars need to be less frequent than those on greens, Rossi said. If collars are put on the same PGR program as greens, they are likely to be overregulated and thin out dramatically.