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.

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:

A summary of photosynthetically active radiation for 1 year at Tokyo

image from www.flickr.com
This chart (download it here) shows the average photosynthetic photon flux density (PPFD) for each hour of 2015 at Tokyo. The daily light integral (DLI) is the number written in black at the top right corner of each facet in this chart.

One can get some idea of how the DLI changes seasonally and with cloudy weather; one can also see how the PPFD changes from sunny to cloudy days at different times of the year.

A chart of PPFD at two locations this year from January 1 through last Friday

The photosynthetically active radiation (PAR) changes through the day and through the year. The PAR is measured instantaneously for a duration of 1 second as the photosynthetic photon flux density (PPFD), and by adding up the PPFD for all the seconds in the day, one gets the daily total of PAR, which is called the daily light integral (DLI).

These charts show the average PPFD on an hour by hour basis. With a look at a chart like this, one can see:

  • how length of the day affects PAR, by looking at what time in the morning and what time in the evening the PPFD goes to 0.
  • how time of the day affects PAR, by looking at the change in PPFD hour by hour through the day.
  • how day of the year, and consequently sun angle, affects the PAR, by looking at the maximum values of PPFD at midday and seeing how they change through the year.
  • how clouds reduce the PAR, by comparing PPFD on sunny hours or days to PPFD on hours or days that don't have full sun. For more about sun and clouds and time of year, see these descriptive slides with data from 4 days in Tokyo this year: a sunny summer day, a very cloudy summer day, a sunny autumn day, and a partly sunny autumn day.

This chart shows, for every hour of this year through last Friday, the average PPFD for that hour at Tokyo (red) and at Watkinsville (blue). Each panel of the chart is a single day, and the DLI in units of mol m-2 d-1 is written on each panel, in red for Tokyo and in blue for Watkinsville.

image from www.flickr.com

There have been 296 days this year, through October 23. On one of these days, February 10, there were erroneous data at Watkinsville, so I don't have a DLI. That leaves 295 days with a DLI for both Tokyo and Watkinsville. These locations have similar temperatures, and similar latitudes. How do they compare for photosynthetically active radiation? There have been 115 days with a higher DLI at Tokyo than at Watkinsville, and 180 days with a higher DLI at Watkinsville than at Tokyo.

I've made a couple other similar charts. This one shows the average PPFD at Tokyo hour by hour this year through October 12. Because the chart shows data for only one location, I've used color to indicate the month.

image from www.flickr.com

And the next one is the same location and dates as the above, with the addition of the DLI written on each panel.

image from www.flickr.com

The Watkinsville data are from the US Climate Reference Network and the Tokyo data are from the Japan Meteorological Agency.

Why light is more important for ultradwarf than for bent: my presentations at the Japan Turf Show

I'm giving two presentations at the Japan Turf Show in Tokyo this week. In the first one, I explain why light, by which I mean photosynthetically active radiation (PAR), is more important for ultradwarf bermudagrass than it is for creeping bentgrass. I use data from Tokyo and from Watkinsville, Georgia, to demonstrate this and to point out the difference in PAR between Japan and the region of the USA with similar temperatures.

The slides for this presentation about light are available in English and in Japanese.

In a second presentation, I talk about management of ultradwarf bermudagrass greens, explaining how this species performs compared to creeping bentgrass in Japan, and how it should be managed.

The slides for this presentation about ultradwarf management are available in English and in Japanese.

"I'd be applying potassium all the time": Part 2

In Part 1, I explained that adding potassium (K) after every precipitation event of 25 mm (1 inch) or more at Minneapolis or Fukuoka would supply from 2 to 13 times more K than the grass could use. Since there is no benefit to adding more K than the grass can use, it doesn't seem that such post-precipitation applications are necessary.

How can one determine how much K the grass will use? This calculator does, predicting how much K is required as fertilizer, all while making sure plenty of K remains in the soil as a buffer even beyond the K that is used by the grass.

And now, this calculator is available in a Japanese version too.


Energy for growth, and weeds

Two things today are kind of related to this topic. One is this -- Jim Brosnan mentioned, and showed photographic evidence, that "weed pressure on Oahu never ceases to amaze."

And I had a conversation with a golf course designer about fine fescue as an infrequently mown rough, in what climates that species can work, and what happens when it is too hot for fine fescue. And I mentioned that one can plant a number of species other than fine fescue in a warmer climate, but the problem becomes one of "how can we find a ball" because there is a lot of energy for growth. Of course there are various techniques turf managers can use to solve that problem, but then the turf will be alive, but thin. It must be if one is going to find a ball in it.

Once there are voids, weeds have an opportunity to grow. Turf managers can solve this problem too, with herbicides, or with manual removal of weeds. But now comes another problem. That is erosion, in locations with substantial rainfall.

Anyway, it must be that the growth of plants (desired species, and weeds) is related to the energy available for the plants to grow. In general the hotter it is, the more energy there will be for weeds, so when one thins a low maintenance rough, the energy for weed growth or invasion is going to be more in a hotter climate than in a cool one. I looked up some data from Japan -- hour by hour data of temperature and global irradiance for 2014 at Sapporo, Tokyo, and Naha. Then I converted the irradiance to photosynthetically active radiation (PAR) using a factor of 2.04.

I looked only at day time, when the sun was above the horizon. And I arbitrarily cut the data to look only at those hours when the temperature was greater than or equal to 20°C. Then I added up all the light, and all the hours. This is a very rough index of how much energy there is for growth, especially for the weeds that will grow when it is hot. And it is a conservative estimate, because the night temperatures influence growth too, and so does the actual temperature. This is just a quick way to note the differences between locations.

At Sapporo in 2014, the cumulative sum of PAR for hours when the temperature was greater than or equal to 20°C was 3,781 mol m-2. Tokyo has 5,844, and Naha was 9,124. Oahu is considerably warmer than Naha, so it almost certainly would have more PAR than Naha at this cutoff value.

Just looking at the time, how many hours were there for weeds to grow well in these different locations, by looking at how many hours there were with a temperature at or above 20°C? At Sapporo, there were 1,365 of these hours; at Tokyo there were 2,503; and at Naha it was 3,805. Again, locations in Oahu would almost certainly be more than Naha.

That is a real quick estimate of how much energy there is for weeds to grow, or more specifically how the energy is likely to differ in magnitude from location to location.

And one more thing -- in Scotland where a fine fescue rough actually works well, how much energy would there be for weeds? I don't have the exact irradiance data for Scotland, so I won't try to compare it to exact measurements. But I can give some idea of just how much lower the energy is, or how much lower the duration of time would be for weeds to grow rapidly. Huge disclaimer is necessary here, because the species are different, so a C3 weed like Poa annua might grow relatively rapidly in Dornoch but I am considering more the C4 weeds like Paspalum dilatatum or Cyperus rotundus.

It still makes an interesting comparison. Of Naha, Tokyo, and Sapporo, Sapporo is by far the coldest. And in the hottest month of the year in Sapporo, the average low temperature is 19.1°C, and the average high temperature is 26.4°C. How about somewhere in Scotland where fine fescue grows well? I picked Leuchars, just north of St. Andrews. In the hottest month of the year in Leuchars, the average low is 10.8°C, and the average high is 19.2°C.

A turfgrass recipe, with ingredients

Today I have two seminars at the 北海道グリーン研究会 autumn meeting. That's the Hokkaidō gurīn kenkyūkai -- the Hokkaido green research association. You can view or download the presentations and handouts at the links below.

The first presentation is called If turfgrass growth were a recipe, these are the ingredients.

There are four main factors (ingredients) that influence growth. These are temperature, water, light, and nitrogen. And one can either measure or control each of them.

Adjusting the growth rate of the grass is what greenkeeping is all about. And being able to measure and control the "ingredients" allows one to compare maintenance at one site to another, compare differences from year to year at the same site, and adjust inputs for different species. This provides a template for improvement of the turf through adjustments to the growth rate.

The second presentation is called How I would manage bentgrass greens today.

I explain how I would measure and control the ingredients of growth, and explain how I would do it differently today than I did 15 years ago when I was a greenkeeper managing bentgrass greens in Japan.