"Anyone who's played golf in Japan will know that many clubs have two greens on each hole"

Selection_101Fred Varcoe wrote about putting greens on Japanese golf courses in the August 2016 issue of Euro Biz Japan. The article, Know your greens (pdf, 3 MB), includes some quotes from me about bentgrass, korai, and how balls roll on putting greens.

For more about the two green system in Japan, see:

And kind of on this same topic, but of more general interest, see Paul Jansen's post on The Japanese Golf Experience.  You'll see more than just grass: breakfast beer, tiny hotel rooms, hot springs, cold springs, blue balls, green tea, and a volcanic eruption.

Shiny app shows the temperature and sunshine combination for 11 cities in Japan


I made a Shiny app with climatological normals data from the Japan Meteorological Agency to show the combination of sunshine and temperature at 11 locations.

@naturalgolf_D asked "What kind of situation is Japan?" With these data, I think it is interesting to compare different locations of interest, and a Shiny app is an easy way to do that.

Six more Shiny apps from ATC are here.

Clipping volume variation from green to green

Ryo Ishikawa won the KBC Augusta tournament at Keya GC in Fukuoka this week. Before the tournament started, he was so struck by the green conditions that he wrote about it on his website.


During the tournament, he putted well, with 27 putts Thursday, 26 Friday, 24 Saturday, and 26 Sunday. He had no three putts and 41 one putts on these korai greens during the tournament.

The greenkeeping staff at Keya GC measure the volume of clippings from 12 greens when the greens are mown. I shared some photos of this process, and some of the results during the tournament this year, in these messages:

I wondered how the clipping volume at Keya GC during the tournament this year compared to other courses. I also wondered if the variation in clipping volume from green to green during the tournament was different from clipping volume variability during a regular week.

To do that, I looked at clipping volume from 7 consecutive days in which greens were mown. Data from Keya during tournament week in 2016 are in the chart below, along with data from the last 7 mowing days at Keya during July 2016, and data from earlier this year from two different courses with cool-season grass.


As far as consistency in the volume of clippings, the tournament data looks impressive. I would expect that this consistency in clipping volume would result in more consistent ball roll on the greens during a tournament compared to everyday play.

I wanted to look also at the variability in clipping volume from green to green on a particular day. Is the variability in clipping volume from green to green lower during the tournament maintenance? To do that, I calculated the coefficient of variation (cv) for these same data. The cv is the standard deviation (σ) divided by the mean (μ).


I like that the cv during the tournament week was on a downward trend. I don't see a huge difference in the overall cv -- the mean cv for these dates is 0.31 for C3 grass #1, 0.37 for C3 grass #2, 0.32 for Keya at KBC Augusta 2016, and 0.32 for Keya during the last 7 mows of July.

One might speculate that greens with the same growing environment and the same soil and the same grass would have a lower cv. The cv shown here may represent some indication of the microclimate effect on growth across a property.

Something you don't see every day

Next week is the KBC Augusta (KBCオーガスタ) tournament at Keya Golf Club in Japan.

This is a rare event -- a professional golf tournament played on korai (Zoysia matrella) greens.

For more about this grass and these type of greens, see:

I may share a few photos and observations from the tournament. If I do, I'll use the #KBCオーガスタ hashtag. You can also find out more about this grass and its maintenance at the Keya Golf Club Turfgrass Maintenance page or by following Keya GC superintendent Andrew McDaniel.

Is it normal to be cloudy like this?

2016-07-17 10.23.40

On July 17, I was in the Tokyo area with Jim Brosnan. The daily light integral (DLI) in Tokyo on July 17 was 14.2 mol/m2. Jim asked me if it was exceptionally cloudy that day. Not really, I answered. I told him that the such cloudiness was normal.

Now that July 2016 is over, I looked at the DLI for every day in July at Tokyo and also at Batesville, Arkansas. Both are at about 35.7°N latitude, so the day lengths will be identical.

The lowest DLI at Batesville in July was 22.8 mol/m2 on July 29. In Tokyo, there were 10 days in July with a DLI less than 22.8 mol/m2, including 5 days with a DLI less than 10 mol/m2. In that context, the cloudiness on July 17 was not exceptional.

To see more, check out the average hourly PPFD and DLI values for Tokyo in this chart and for Batesville in this one.

Warm-season turfgrass growth rates and competition at 35°N

Mike Richardson pointed out that the growth rate of zoysia is less than bermuda, so by implication there must be something other than growth rate that allows zoysia to invade bermuda. That is, in the situations when bermuda and zoysia are growing together -- competing -- when zoysia appears to grow faster, Mike suggests it may be a factor such as turf density that allows such a result, because bermuda grows faster than zoysia.

I've outlined a hypothesis about grass growth rates and their required inputs, and have more to write about that later. In that hypothesis, I mention location, and in my recent discussion with Mike about the growth rate I said that there is a variety by climate interaction. By climate, I mean the same as location. I'll use these words interchangeably.

Let me try to explain what I mean by an interaction by climate. I'll use data from Tokyo, and from Batesville (2016 data) and Fort Smith (climatological normals data). These locations are all about 35°N.

Light, temperature, plant water status, and leaf nitrogen content all influence growth. In turfgrass management, light and temperature generally can't be controlled; plant water status and leaf nitrogen content can be modified by turfgrass managers. We can imagine that bermuda and zoysia are growing side by side, or together, and then think of what may happen with modifications to these growth-influencing factors.

On average, this is the part of the climate that can't be controlled, at Fort Smith and at Tokyo, shown in 2-dimensional space.


That's a similar temperature range but different amounts of sunshine. Thus, there is no overlap during the months when warm-season grasses are growing. I focus on light and temperature because the water and the nitrogen can be adjusted by the turf manager.

Temperatures for 2016 are pretty similar through July 30. I express temperature here as the cumulative sum of growing degree days.


Ok, so temperatures are similar. If it were only temperature that influences growth, one would expect the grasses to perform pretty much the same at these locations. If bermuda does have an inherently faster growth rate than zoysia, then in this side-by-side comparison, with the same temperature, then bermuda should grow faster at both locations.

I downloaded the global solar radiation data also and then converted it into photosynthetic radiation units. This is Batesville for the first 7 months of 2016.

2016 Batesville DLI and PPFD through July 31

This is Tokyo for the first 7 months of 2016.

2016 Tokyo DLI and PPFD through July 31

In 2016, there has been more photosynthetic light at Batesville than at Tokyo.


The DLI was pretty much the same from January to March, but since the start of April Batesville has jumped ahead by about 1,000 moles/m2. In the past 4 months, Tokyo has accumulated about 4,000 mol/m2 and Batesville has accumulated about 5,000 mol/m2. That's a log percentage difference of 22%. The difference has been especially pronounced in June and July -- the hottest months of the year so far.

Imagine growing bermuda and zoysia in 10% shade at the same temperature. Bermuda may grow faster than zoysia. Now imagine 20% shade. Probably the same result. How about 30, 40, and 50% shade? 60% or 70% shade? At some point, the growth rate of zoysia will be greater than the growth rate of bermuda. The bermuda will die in shade under which the zoysia can still produce a turf.

Consider now that there are varying growth rates among bermudagrass varieties, and also among zoysia varieties. That's what I mean by the location (or climate) by variety interaction. Take an inherently faster-growing zoysia, mix it with bermuda, grow it in a climate with high temperatures combined with lower DLI, mow the grass and make sure plenty of water is applied during the dry season, and see which one grows faster. It's not bermuda.

Yes, with a high DLI, plenty of fertilizer, moderate water supply, and high temperatures, bermuda grows faster than zoysia. Here's a photo of the ATC research facility putting green during grow-in. It's easy to tell which plots are zoysia -- those closest to the camera.

grow-in 22 dec

But if one thinks of growth as something that happens over years, at a location, with the grasses maintained as turf, then one can find the growth rate of zoysia can be higher than that of bermuda.

I find it useful to look at growth rate in those terms, rather than trying to explain it as a response to density or as competition for some other factor.

99 article titles


I've been writing a monthly article for ゴルフ場セミナー (Golf Course Seminar) magazine since May 2008. That's 99 articles so far, and 118,518 words. The best of these will be published in English, sometime; for now they are only available in Japanese. The first 36 of these articles are available in PDF format here.

Starting in May 2008 (#1) and going up to July 2016 (#99), these are the article titles in English.

1. What is Greenkeeping? The 6 Basic Principles
2. Soil Water: How to Manage it in the Summer
3. Fertilizer for Grass: Soil, Leaves, and Growth Potential
4. 5 Maintenance Activities That May Increase Roots
5. Coring: Do it Right, and Get Better Greens
6. Simple is Better: An Amazing Experiment at Rothamsted
7. Sand Topdressing by Numbers
8. 2008 International Turfgrass Science Quiz
9. Why is Grass Green?
10. 2008 International Turfgrass Science Quiz - Answers & Discussion
11. Golf Course Maintenance Expenditures in 2009
12. Putting It All Together: summarizing the six points of greenkeeping
13. The most important thing to know about creeping bentgrass
14. The 2009 US Open, Bethpage Black, and Integrated Pest Management
15. Effective spraying: nozzles, water volume, and droplet size
16. The Critical Component of Putting Green Management
17. The Critical Moisture Content of Soils
18. Some New Turfgrass Research Results
19. The Optimum Level of Plant Nutrients in the Soil
20. A Christmas Gift List for the Turfgrass Scientist
21. Two Equations for the New Year
22. Old and New, from Scotland to China
23. Roll Three Times a Week for Better Greens
24. Turfgrass Maintenance by the Numbers
25. Current Trends in GC Maintenance
26. Thatch: Definition & Management
27. Does Phosphorus Cause Algae on Putting Greens?
28. Pebble Beach Putting Greens: Playing Condition vs. Appearance
29. One Good Thing About the Summer
30. The Foundation for a System of Golf Course Maintenance
31. Practical Application of Turfgrass Science Principles
32. Labor Analysis and Priority of Maintenance Work
33. A Scientific Guide to Turfgrass Maintenance this Year: Part 1
34. A Scientific Guide to Turfgrass Maintenance this Year: Part 2
35. A Scientific Guide to Turfgrass Maintenance this Year: Part 3
36. Data + Science + Technique = Better Grass Conditions
37. How Poor Greens Became Excellent Greens at Vietnam: a case study
38. Tublamu Navy Golf Course & the 2004 Indian Ocean Tsunami
39. Thai Country Club: Great greens with terrible water
40. An Almost Insurmountable Problem: nematodes
41. What’s in the irrigation water at the Home of Golf?
42. Converting to Ultradwarf Bermudagrass: why and how
43. Choosing Soil Moisture Meters
44. Using Soil Moisture Meters
45. Firm Putting Greens at Australia
46. Fertilizing Greens in the West Coast Style
47. Using Soil Test Data to Improve Turfgrass Conditions
48. A Common Cause for Putting Green Problems
49. Rolling Greens: What do the Data Show?
50. Green Speed and the Brede Equation
51. Cooling the Soil
52. Soil Moisture Content of Putting Greens in Japan
53. The Clegg Hammer and the “Hardness” of Putting Greens
54. Cooling the Soil at Night
55. Measuring Photosynthetically Active Radiation
56. Green Speed Variability
57. Green Hardness: Yamanaka Tester vs. Clegg Hammer
58. The Surface and Soil Temperatures of Putting Greens
59. The pH, N, P, and K of Putting Green Soils in 2012
60. The Ca, Mg, S, and Micronutrients of Putting Green Soils in 2012
61. Measuring the Reliability of Putting Greens
62. Putting Green Soil Moisture Content and Management in Summer
63. The Effect of Rolling on Green Speed and Green Hardness
64. Putting green surface temperatures and syringing
65. Fertilizer planning and nutrient mass balance
66. Green Speed Summary
67. Temperature-based growth potential: a study in 3 seasons
68. What is the effect of day length on turfgrass growth and nitrogen requirement?
69. Organic Matter Management in Putting Greens
70. When is the best time to core aerify putting greens?
71. A new way to look at turf nutrient requirements
72. A Method to Predict the Optimum Time for Overseeding
73. A counterintuitive approach to irrigation
74. An important note on the timing of growth regulator and nitrogen applications
75. Anthracnose and healthy greens in summer
76. New research about management of thatch and organic matter on putting greens
77. How many nutrient cations can a green hold?
78. Fertilizer, leaching, and cation exchange capacity
79. What do wetting agents really do?
80. Nitrogen fertilizer — when it is used by the grass?
81. Does nitrogen fertilizer increase or decrease roots?
82. Temperature, humidity, and combining them for summertime heat indices
83. Mowing and the 1/3 rule
84. Timing of nitrogen application to greens
85. Putting green performance tests: professional estimates
86. A new summary of putting green stimpmeter, surface hardness, and soil water measurements
87. Are summer nights getting hotter?
88. Fine fescue putting greens and tournament golf
89. Wind, tournament golf, and the 5 day Open Championship
90. Some useful things to understand about light
91. An analysis of three years of tournament green hardness data
92. An analysis of three years of tournament green speed data
93. What do P and K mean, exactly?
94. Two methods for precision water management
95. Course conditioning guidelines for PGA Tour tournaments
96. How much does water use vary from green to green?
97. The combination of temperature and sunshine to compare locations
98. What’s the irrigation water requirement?
99. Green speed, pace of play, and more green speed

A little more data to support an anecdote

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.

Data to support an anecdote

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.

Animated charts showing photosynthetically active radiation for a year

I spoke at the Sustainable Turfgrass Management in Asia 2016 conference about light at different locations. The presentations slides can be viewed here, or embedded below. For more about the conference, which saw 278 delegates from 24 countries and 5 continents travel to Pattaya this year, see this post at the Asian Turf Seminar site.

Light is important. Without enough light, grass won't grow well. I suggested that "no-problem" daily light integral (DLI) values for putting greens of bermudagrass, seashore paspalum, and zoysiagrass, may be about 40, 30, and 20 respectively. And I showed what PAR is, and how PAR is measured in one second as the photosynthetic photon flux density (PPFD), and then how all the PPFD over the course of a day are added together to make up the DLI.

I showed charts for one day, and also animated charts that show PPFD and DLI for every day of the year. This chart shows the maximum expected PPFD by time of day, and maximum possible DLI by day of the year, at Tokyo and Bangkok if there were no clouds. You may need to click the browser's "refresh" button to play these animations.


I wanted to visualize how these maximum possible values, on days when the sky is clear and about 75% of the extraterrestrial radiation reaches the earth's surface. To do that, I looked up the global solar radiation for Tokyo for every hour of 2015, converted those values to PAR units, and plotted them together with the maximum possible values assuming 75% transmittance of extraterrestrial radiation. That is plotted here.


I also explained that the global solar radiation has a large influence on the evapotranspiration (ET). I demonstrated this ET calculator that uses the Hargreaves equation to estimate the ET based on global solar radiation.