Core aerating putting greens, or not
There was an article on the Golf Course Industry website about a course that hasn’t core aerified putting greens since the course opened 12 years ago. It’s a short article—466 words. That’s shorter than a lot of posts on this blog. There’s not much information in the article, but I thought it interesting enough to share.
Chuck Barber replied with an intriguing question and comment:
Can I ask?: Why do people want me to know they don’t have to/never have had to core aerate greens? A course in the desert probably doesn’t have much in the way of OM accumulation to deal w/, monsoon rainfall displacing air on a native soil green, etc. What is good for the goose is not necessarily good for the gander, or so I am told. I have always been clear/consistent on why I choose to core aerate greens. It drives me a little crazy that it has become a badge of honor to not do that.
Brandon Horvath responded too, noting that “That ‘recipe’ will perform very differently in different climate regions.”
1. Producing the desired conditions
I’d look at this topic in terms not of core aeration, but as maximizing the ratio between playing conditions and the work required to produce them. I explained that further as:
For any location, there is a certain set of conditions one is trying to produce. And whatever conditions end up being produced, it took a quantifiable amount of work to produce them. One can then express the conditions divided by the work as a ratio. A larger ratio is better.
I’d encourage every turf manager to produce the best possible conditions with the least amount of work. It seems clear that if core aeration is required to produce the desired conditions at a particular location, then that work can easily be justified.
2. What I really think about core aeration
For many years, I didn’t focus so much on the site specific optimization, and rather described what the standard maintenance is. That’s 15 to 20% surface area removal each year, and 12 to 15 mm of sand topdressing. I was writing about that, teaching that, recommending that, and the Managing organic matter in putting greens article by Moeller and Lowe in the Green Section Record in 2016 continues to recommend that much coring:
These articles recommend core aeration treatments that impact 15-20 percent of the putting surface each year and topdressing programs that incorporate at least 40-50 cubic feet of sand per 1,000 square feet annually. These recommendations are still relevant, but some facilities may need more or less [based on site conditions].
That’s the standard recommendation. When I used to recommend that in 2006 and 2007 and 2008 and 2009, turf managers would tell me that “they couldn’t possibly disrupt the surface that much.” They might want to do so, but they couldn’t because of busy tee sheets. I would respond with, “ok, I understand, but when you start to see problems with these surfaces, you’ll have a good idea of why that is. At some point you’ll need to deal with the organic matter.”
But I kept seeing these courses in various parts of the world, doing way less than 15-20% surface removal, and usually putting 3 to 7 mm of sand topdressing rather than the recommended 12 to 15 mm. And you know what I noticed? The surfaces didn’t fail. In 2009 they were fine, and in 2010 they were fine, and in 2015 they were fine. In fact, I’ve seen (and written about extensively on the blog) the surprising case of Keya GC in Japan, where playing conditions actually got better when coring and topdressing were reduced.
I couldn’t keep teaching seminars and writing articles about the standard recommendations when I’d gone almost a decade seeing turf managers not follow these recommendations and still get terrific results. By 2016, I was writing an article for my column in Golf Course Seminar magazine with the title I’d recommend less coring and less topdressing sand than I used to.
I’ve given seminars about this too. I think these slides from my presentation at the Spanish Greenkeepers Congress in 2018 are especially easy to follow.
The slide embedded below shows a creeping bentgrass green, very much in the transition zone, that hasn’t seen coring tines for 13 years.
3. Why I think it is worthwhile to highlight alternatives to the standard recommendation
When an article is written by USGA agronomists and is published in the Green Section Record, I consider that to be a somewhat official recommendation. As recently as 2016, the standard official recommendation continues to be 15 to 20% surface area removal and 12 to 15 mm of sand topdressing.
I think it is pretty easy to justify doing the work necessary to produce the desired conditions at any facility, and I would hope that some of the information here at the ATC website is useful in that regard (see for example the most-read post of all time from this site, from 2009, on Core aeration of Putting Greens…how much is enough?).
At the same time, when there are standard recommendations that are widely known—certainly more widely known than the barely-read content that I produce—I find it worthwhile to share and highlight some of those situations where an alternative to the standard recommendation is producing good results.
Any “badge of honor” should be in producing the desired turf conditions with the least amount of work. There’s no badge of honor in not core aerating.
- Organic matter reduction by hollow-tines, solid-tines, and sand topdressing
- Hollow-tine cultivation and solid-tine spiking both failed to alleviate summer bentgrass decline
- Cleaning cores the easy way
- An especially lucid abstract about core aeration
- Mental models, soil organic matter, and chocolate bars