One is an article, another is a podcast, and you won't regret the time spent reading the first and listening to the second.

First, the 4 November issue of the Green Section Record contains Managing Organic Matter in Putting Greens by Adam Moeller and Todd Lowe.

This article explains that "there are many agronomic programs that influence the playability and health of putting greens, but organic matter management is arguably the most important." It goes on to explain the standard practices in 2016.

Moeller and Lowe conclude that "traditional programs", and by that they mean programs that include core aeration, "still provide the most consistent results for managing organic matter and improving putting green conditions."

This is a really good article for referencing what is standard in 2016, but I'm not in full agreement with their conclusion. I used to think that coring was essential, but over the past few years I've changed my thinking. More about that in the footnote.

The second item is the recent TurfNet Radio podcast with Frank Rossi and Chris Tritabaugh about managing for the Ryder Cup. If you listen to this, you will find that they discuss organic matter on putting greens (and a lot of other interesting things), but if you haven't heard, there has been no core aeration on the greens at Hazeltine since 2013.

Point of reference; these greens have been cored once since I've been here. August of 2013, never since. https://t.co/qfFccR2qV0

— Chris Tritabaugh (@ct_turf) October 1, 2016

The article says coring provides the most consistent results, and the podcast explains how greens are managed to a high standard without coring. It's good to be informed about this topic, so that you can be sure to make the right choices for any turf that you manage.

Footnote: I used to recommend the removal of 20% of the putting green surface area by coring each year and the annual addition of at least 12 mm of sand topdressing. I don't make that recommendation anymore.

Rossi and Tritabaugh talked about the grass yield and growth rate. How much was the grass growing? The idea being that one can match the quantity of sand applied to the rate of grass growth, thus avoiding coring by maintaining a consistent organic matter content at the soil surface. But they did not put a number to the growth rate. I think it is possible to put a number to the growth, and from that to make a site specific plan for organic matter management.

Consider the "new" bentgrasses with high shoot density, or ultradwarf bermudagrasses, widely considered to be prolific thatch producers. Please consider now how much thatch bentgrass will produce in Bangkok, or how much organic matter Miniverde will produce in Moscow. None, right? Now please continue that thought experiment a step further, and consider how much thatch (or organic matter) grasses produce when they grow slowly, supplied with just enough nitrogen and just enough water to produce the desired growth rate. Supply no N and no H₂O to ultradwarf bermudagrass and there won't be any organic matter to manage. Is it possible that there is a level of growth at which minimal topdressing and no coring produce the desired surface? That's the goal, and I think it is possible with careful attention to the growth rate.

And that avoids (or at least minimizes) the putting surface disruption associated with coring too.

For more about this, see:

• Data to support an anecdote
• A little more data to support an anecdote
• Measuring and tracking grass clippings
• More about the measurement of grass clippings
• Clipping volume variation from green to green
• A short grammar of greenkeeping
• Reducing soil organic matter with H₂O₂

Yesterday I wrote about soil organic matter decreasing over a 3 year period, even though the greens had only been cored twice in that time, and sand topdressing amounts had been reduced each year.

17th green after coring in May 2013

When I think about reducing organic matter, I usually think of removal or dilution. Removal would be through coring or scarification; dilution would be by mixing sand with the organic matter.

12th green after 12 mm core aerification and topdressing in May 2013

But in this case, I think the organic matter in the soil is going down because the organic matter production is less than the organic matter decomposition. The reason I think this is simple. There hasn't been much removal or dilution of organic matter in the past 3 years, but the organic matter has still gone down.

The 14th green in August 2013

In the comments to yesterday's post, there was some discussion of layering if sand was not applied often enough. I agree that undesirable layering might occur, but only if the grass was producing organic matter faster than it was decomposing.

To put this into context, I added up the volume of clippings from the greens in 2015, to give some idea of the growth rate at which the maintenance work described yesterday has led to a decrease in soil organic matter.

Add that up for the year and it is 270 L/100 m². Measurements of the fresh weight of clippings on these greens give 0.3165 kg for each liter of clippings, so that is 85 kg of fresh clippings per 100 m². I expect these clippings are about 70% water and 30% dry matter, so I've estimated the dry weight of the clippings at 26 kg/100 m².

That gives three estimates of how much the grass is growing at this location. Those numbers might be useful if you'd like to compare the growth of grass where you are.

As an aside, these types of calculations are how I estimate nutrient harvest. If you've been to one of my seminars about how to use the MLSN guidelines, I will have described that the use of the guidelines involves taking the amount the grass will use (I'll call that a), adding that to the amount I want to make sure remains in the soil, which is the MLSN guideline (I'll call that b). These values a and b, together, are the amount of an element we want to be sure is present. a + b represent the amount we want to have. The amount we actually have is measured by the soil test, and I call that c. It follows that the amount of an element required as fertilizer is the amount we want to have, minus the amount we do have, represented in an equation as a + b - c.

Last week I received the latest soil tests from Keya Golf Club, where Andrew McDaniel is the superintendent. I'm sharing the organic matter results from the greens, because I think they will be of general interest. This chart shows the soil organic matter % on the greens for samples taken in early 2013, 2014, 2015, and now 2016.

Now for a bit of a tangent, and then back to the work that's been done at Keya since 2013. It would seem that not core aerifying, and not topdressing all the time, would be considered alternative maintenance. Another way to look at it is that the management of soil organic matter -- the amount of work required in that regard -- will be proportional to the growth of the grass.

I remember a conversation I had once during break time at a seminar in New Delhi. "Tifeagle and other ultradwarf bermudagrass varieties accumulate too much thatch," someone told me, "and will require almost constant and aggressive verticutting to keep it under control." I disagreed, pointing out that the amount of thatch (organic matter) control required will be related to how much the grass grows. "Tifeagle in Siberia won't produce any thatch at all," I said.

As an example, this is Zoysia japonica in late July in Yorkshire, surrounded by cool-season grasses. The zoysia is not producing much organic matter at all, and there's no need to verticut or topdress or core.

Another example: this is Penncross in Thailand. It germinates, but doesn't require mowing. If you can keep it alive, you certainly don't have to worry about organic matter management.

Rather than prescriptive recommendations of surface area to be removed by coring (I've recommended this in the past) or the quantities of sand that should be applied as topdressing (I've also recommended this in the past), I now think it is more reasonable to consider the growth rate of the grass, and to manage the organic matter as required based on the growth rate.

Ideally, there will be no coring, minimal verticutting, and minimal topdressing. That's easier, and it causes less disruption to the playing surface. Such an approach may not be possible, but I prefer to have my ideal as great surfaces all the time, with minimal disruption, compared to the alternative ideal of great surfaces except when coring to remove x % of the surface area each year while applying a total of y mm of sand per year.

Back from that tangent to the greens at Keya, where the organic matter on greens has been going down since 2013.

If one does a regression on these data, for each day that passes, the organic matter in the top 10 cm of the soil has gone down by 0.005 g per kg. In 365 days, the reduction is about 1.8 g/kg.

Here's where the data support an anecdote. The anecdote is, managing the growth rate allows one to minimize or eliminate coring.

The N rate on these greens in 2013, 2014, and 2015, respectively, has been 14.6, 9.5, and 10.6 g/m². That is still enough to produce a dense korai turf (manilagrass or Zoysia matrella).

Coring and solid-tine aerification has been minimal and has decreased while the greens have only improved. 12 mm core in May 2013, 12 mm solid in July 2013, 12 mm core in June 2014, and 13 mm solid cross tine in July 2015. That's not much, and the organic matter is going down.

Greens were verticut 3 times in 2013, 3 times in 2014,and 4 times in 2015.

Topdressing amounts have been 8 mm in 2013, 4.6 mm in 2014, and 3.8 mm in 2015.

You see the trend? Core aerification is done infrequently, sand topdressing is applied less and less, N fertilizer is applied at a reasonable rate, and the soil organic matter goes down. It's a viciously good cycle.

I don't know what the potential is for these turfgrass topics, but I'm glad to see the visitors to the site have been increasing each year.

And the one blog post that has gotten the most views? It's this one about core aerification, with more than 6,000 pageviews since I posted it in July 2009.

When I talk about organic matter management, sand topdressing, core aerification, minimizing disturbance to golfers – those and associated topics – I often show a chart such as the one at right. 

I've made a series of new charts, all showing the same data, but with the units given in both metric (cm and mm) and in U.S. customary units (inches). These charts are shown below and are provided in 2 versions – in colour or with different line types to show different spacing. Click the charts below to see at full size or to download a medium resolution copy.

Metric, linetype

Inches, linetype

Metric, color

Inches, color

The temperature-based turfgrass growth potential predicts how grass growth can respond to temperature. This growth potential (GP) was developed by PACE Turf and has been put to many uses such as predicting the time of overseeding, estimating turfgrass nitrogen requirements, assessing turfgrass stress, and evaluating growth and optimum times for various maintenance practices.

When the temperatures are not conducive to growth for cool-season (C3) or warm-season (C4) grasses, there isn't much one can do to force the growth. Extra nitrogen can be added, but it really doesn't have its full effect until the temperatures get into an optimum range for growth.

@asianturfgrass @paceturf having a tough time healing in from aeration. Been almost 4 weeks.

— Chris cook (@brgcsuper) April 14, 2014

After reading that tweet, I looked up the temperature data for Tulsa. Sure enough, the growth potential for C3 grass has been pretty low for the past month. Growth potential of C3 and C4 grasses at Tulsa are plotted in this chart, with data included for the past 472 days, from 1 January 2013 until 17 April 2014.

I find the growth potential useful in a lot of ways. On golf courses with both cool and warm season grass, as at Bristol Hill Golf Club near Kisarazu, it can be useful to study the growth potential when planning maintenance activities.

Cool season (C3) and warm season (C4) grass at Bristol Hill Golf Club near Kisarazu, Japan

The GP at Kisarazu for the past 472 days is show below. Ideally, disruptive maintenance practices such as scarifying or core aerification will be done at times when the turf has a high growth potential. This allows for a rapid recovery time and minimizes disruption to play.

I looked up the data for a couple other cites. At Sydney (data from the Sydney Airport), the temperatures are milder.

At Dubai, the temperatures are more extreme.

 With all the variation in temperature from place to place, there is also a big difference in the way grass will respond. The growth potential puts a numerical value to this. This can then be used in maintenance planning, in useful comparisons to other locations, or in explanations of why the turf is responding in a certain way.

Various interesting posts hide in the back pages of blogs, and I've enjoyed seeing which of the posts from the early years of this blog were most popular, as measured by the number of pageviews.

Continuing with the lists of top posts by year since the inception of this blog in 2009, here are the 5 posts with the highest pageviews from 2012:

1. Five Articles Every Greenkeeper Should Read
2. Chemical Fertilizer Programs for Sand Based Rootzones - the 1 minute version
3. The Real Price of Fertilizer
4. Putting Green Fertilizer: getting it right
5. Calcium deficiency in turfgrass, an imaginary problem?

I previously listed the 5 top posts from 2009, the top 5 from 2010, and the top 5 from 2011.

Coming up next week, I'll share some of the most viewed posts of 2013.

The Japan Turf Show is one of my favorite events of the year. In fact, I like the show so much that I wrote a remote report for the 2012 show that I could not attend. This year I did attend. I taught a seminar about ultradwarf bermudagrass and how it compares to creeping bentgrass as a putting green surface in Japan.

What are my favorite things about this show? For one, it is fun to meet with old friends. I saw Fujihira-san at the show this year. He and I worked together at Habu CC thirteen years ago, where he was the assistant equipment manager; he is now the equipment manager at a new course in Chiba prefecture.

There is also the education, with six seminar rooms offering concurrent sessions on a range of topics. On the afternoon of the first day, a packed crowd of delegates filled seminar room A to listen to a panel discussion about ultradwarf bermudagrass. The presenters were representatives from companies providing Champion, Miniverde, and Tifeagle in Japan. 

Although ultradwarf is a subject of interest, most putting greens in Japan are creeping bentgrass. After my presentation, I had a look at some of the creeping bentgrass on display.

Japan Turf Show. Bentgrass お話し with @asianturfgrass with Kasumigaseki Super @ManzanSimizu pic.twitter.com/swEiAMa0XF

— Benjamin Warren (@benjaminwarren) November 14, 2013

Another great thing about the Japan Turf Show are the products one can find only here. For example, there is the Yabuta Co. drop seeder that can precisely spread seed at rates down to 1 g/m². That is the equivalent of 0.2 lbs/1000 ft², and is especially useful for precise application of creeping bentgrass seed.

 Mr. Yabuta showed me one of his new inventions this year, the Cup Dr., which is available in small or large sizes for rolling the area around the cup after changing the hole location.

Then there are the multitude of tines and blades for cultivation equipment. The 4 mm hollow tine (0.16 inches) is becoming quite popular.

With all these tine sizes available, there is no excuse not to calculate the surface area affected at each time of core aerification, and to try to optimize that in a way that will maximize surface area removal while minimizing disruption to play.

If I were a greenkeeper, I would look to remove 5% or more of the surface area at each time of coring, and to do that with conventional tine spacings it is necessary to use 10 mm or larger tines. The 4 mm tines have their place, but are not really useful for substantial removal of organic matter or incorporation of sand into the soil profile.

With all these fun things to learn about, I'm already looking forward to the 2014 Japan Turf Show.

I started this blog on 1 January 2009. After nearly five years of writing, I thought it would be interesting to look back at the most popular posts of each year. There is a lot of information in the back pages of the blog.

In 2009, almost no one read what I was writing. Now, there are more visitors to the blog on a slow day than there were on the busiest day in 2009.

So what were the most popular posts (as measured by pageviews) in 2009? Here they are.

1. Mowing Patterns & Grass Color
2. Core Aeration of Putting Greens ... how much is enough?
3. Sodium Chloride for Weed Control
4. Seeded Sea Spray Seashore Paspalum
5. Turfgrass at Dubai

Coming up I'll share the most popular posts of the succeeding years. 

This week's issue of the USGA Green Section Record has two articles that I really enjoyed reading. One, by MacDonald Niven, explains the value of course maintenance standards and give links to many resources that can help in the development of standards for your club. I've written about maintenance standards before, and I've spoken about their value at various seminars, but Niven explains their value much better than I ever have. He summarizes the key benefits:

• organizing and analyzing priorities for golf course maintenance
• developing an accurate budget to support desired standards
• the maintenance standards document becomes an effective communication tool to share with golfers, decision makers, and the community
• written maintenance standards eliminate emotion and subjectivity when evaluating the effectiveness of the maintenance department

I have sometimes described maintenance standards as being essential because they define what the course maintenance department is actually trying to achieve. The work can be done most efficiently if we know exactly what type of conditions we are trying to produce.

Another article gives an excellent and novel technique (at least to me) for reclaiming bermudagrass putting green edges that have been contaminated by another type of grass. Todd Lowe has written some excellent articles that I have highlighted before, on off-types in ultradwarf greens and on new trends in ultradwarf putting green management, and this one, Reclaiming Putting Green Edges Using Core Aeration Plugs, is a must-read for anyone who manages warm-season putting greens.

Lowe writes that "plugging perimeters with aeration cores offers a practical solution to encroachement of rough-type bermudagrasses into bermudagrass putting greens." After reading the article, I believe that this method can be used not only with bermudagrass greens, but also with seashore paspalum greens or manilagrass greens. The method involves identifying the original green edge, killing the encroaching grass with a non-selective herbicide, removal of the contaminated turf with a sod cutter, and then core aeration of the greens with the cores being pushed into the prepared areas at the green perimeter. 

The USGA Green Section Record is a great source of turfgrass information and is available with a free subscription.