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.

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.

A hypothesis about the most sustainable grass

I've written about zoysia growing faster than bermuda. Mike Richardson asked "is that better? Slow growing has always been one of my favorite traits of zoysia."

I answered that it is better, and that I would explain my hypothesis later. Here it is:

The most sustainable grass for a given location is the one that has the most growth per unit of N and per unit of H2O applied.


  • most sustainable grass is the one that requires the fewest inputs to produce the desired surface
  • location is the temperature and light combination. For more about this see climate.asianturfgrass.com.


  • one considers all the grasses that could possibly produce the desired surface at that location
  • from those, one selects those that don't die when N and H2O are reduced

It follows that of the remaining grasses -- those that don't die -- the one with the fastest growth rate will require the fewest inputs to produce the desired surface, because one can supply low amounts of N and water to that grass. The one with the fastest growth rate also gives the most maintenance options, because one can adjust the growth rate across a wider range.

For more about this, see:

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.

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.

Burning grass



Posted by 岡山後楽園 on Tuesday, February 2, 2016

Korakuen in Okayama is one the three great gardens of Japan, and I like it especially because of its expansive noshiba (Zoysia japonica) lawns. In early February every year, a shiba yaki (grass burning) ceremony is held at Korakuen, when the lawns are burned.

The video above shows the ignition of a lawn. The Facebook page of Korakuen has more photos of the shiba yaki ceremony this year.


Posted by 岡山後楽園 on Wednesday, February 3, 2016

It is pretty amazing how strange it looks before the lawns start to grow again.


Posted by 岡山後楽園 on Wednesday, February 3, 2016

For more about grass burning in Japan, see:

"Can you send me anything that explains the differences between matrella and japonica?"

I sure can. The first thing I look at for different species is the Kew RBG GrassBase. Here are the entries on Zoysia matrella (manilagrass) and Zoysia japonica (japanese lawngrass).

Both are perennial, mat forming grasses. When they are mown, the visual distinction is in the width of the leaf blade. The manilagrass leaf blade tends to be 1 to 3 mm in width; the japanese lawngrass blade is wider, from 2 to 5 mm. There are other distinctions, but the main one is simply how fine or how coarse the turf is.

Zoysia japonica mown at 15 mm

Above is japanese lawngrass, and below is manilagrass. These grasses were grown on the same soil, near Bangkok, with the same fertilizer and mowing and irrigation. The visual difference one sees is in leaf blade width.

Zoysia matrella mown at 15 mm

These photo galleries of manilagrass (Zoysia matrella) and japanese lawngrass (Zoysia japonica) show more distinctions between these species, as well as their appearance and use.

The other big difference in the species is their area of adaptation. Japanese lawngrass is more cold tolerant, and generally grows in places where there is a winter and the grass goes dormant. Manilagrass is a tropical grass, native to areas where the grass does not go dormant. As a turfgrass, manilagrass can be used in locations where there is a winter. But in places with winters colder than Tokyo, there is some risk of winter damage on manilagrass, while japanese lawngrass could still tolerate those winter temperatures.

Does sandcapping affect playability? And does species selection?

I get to talk about two of my favorite topics today. In our 1 day seminar on designing, building, and maintaining golf courses, course architect Paul Jansen will be speaking about 3 main topics:

Where do I come in? I'm going to hone in on the ground contours part, and discuss how the soil and grass conditions affect how a ball will bounce and roll. One can design and build all these great features, but if the sward isn't right, the playability won't be either.

A quick summary of my thesis is this -- sandcapping ain't so great because once one introduces a sand profile, the organic matter must be managed or it will fail. That happens by default for putting greens -- usually -- but almost never on 10++ hectares of fairway turf. And using grasses that don't die allows one to apply less N and water. That leads to firmer surfaces that are better to play on when one wants ground contours to be interesting.

Here are three ways to follow along.

First, my presentation slides are here:

Second, I shared a 2 page PDF handout at the seminar. Download it here.

Third, the above slides and PDF, along with links to all the articles and the video from the presentation, are in this online handout. For convenience, I reproduce all those links here:

Silica and Green Speed

This is something that has never made sense to me. Actually, it seems ridiculous. Zoysia greens are not renowned for being especially fast. But zoysia has especially high silica content in the leaves. Duble, writing about Zoysia: "The species vary from extremely fine textured to coarse textured types and the leaf blades are very stiff due to a high silica content."

So if silica does make greens faster, shouldn't zoysia greens be lightning fast?

I was reminded of it this week, so I checked Nikolai's fine book, The Superintendent's Guide to Controlling Putting Green Speed, on the topic. I'd heard that silica application is supposed to increase green speed by making the leaves more turgid. I looked up the topic in Nikolai. He mentioned one study by Trenholm et al. on seashore paspalum in which silica application led to "increased turgor pressure of the turfgrass leaves."

Then, Nikolai had this short statement:

"For this reason, it is assumed that silica might enhance green speed, but, unfortunately, no study has tested this notion ... Clearly, more data is needed on this subject."

The book came out ten years ago. Anyone have some data on this subject since then?

I've reviewed 540 stimpmeter readings I made in 2011. These greens were in Japan, Vietnam, USA, Philippines, India, and Thailand. The species are listed in the table below, along with the average green speed by grass species.

species # of measurements average speed (feet)
creeping bentgrass 249 8.7
bent-poa 18 9.9
bermuda 107 8.5
fine fescue 15 8.6
zoysia 42 7.8
seashore paspalum 90 8.2
Poa annua 19 9.9

This is nothing against zoysia greens. Zoysia greens can be quite good.

Above is the 18th at Wack Wack during the Philippine Open. Below is roll on a zoysia green at Keya Golf Club in Japan.

The roll can be excellent. But it takes a lot of work to get the conditions shown. Just a high silica content of the leaves, and a high turgidity of the leaves contributing to faster green speed? I don't get it.

Zoysia and growth potential in Beijing and Seoul

This chart shows the temperature-based growth potential for cool (C3) and warm (C4) season grasses at Beijing and Seoul.

It is too cold in winter for any type of grass to grow, and during the spring, summer, and autumn, C3 species will grow more than C4 species. Of course, C4 species use less water than C3 species, tend to be more salt tolerant, and in this type of climate, will require less mowing due to the shorter growing season.

Playing golf on a Zoysia japonica fairway near Seoul, March

Zoysia japonica is in common use as a fairway and rough turf around Seoul, more so than it is in Beijing.

Bentgrass greens and Zoysia japonica through the green near Seoul, March

Based on the similar temperatures between Seoul and Beijing, Zoysia japonica would certainly perform well in the summer in Beijing. But with colder winters in Beijing than in Seoul, one would need to be more concerned about potential winterkill. It would seem that Beijing winters would be almost too cold for Zoysia japonica, based on the temperatures at which this species was killed in this experiment by Patton and Reicher.

March golf near Seoul