The Turfgrass Genki Level
Micah Woods
6 April 2019
I’ve been thinking about turfgrass growth and the relative degree towhich the turf manager is pushing the grass to grow with fertilizer,
or is trying to slow the growth from what it could be by withholding
fertilizer, for a number of years. In a series of posts from February
2019, all published at www.asianturfgrass.com, I explained how
the genki level concept works and its practical applications. This
document puts those posts together in pamphlet form.

Micah Woods, Ph.D., scientist, consultant, author, world traveler, andfounder of the Asian Turfgrass Center,has conducted research and taught
about turfgrass in more than 20 countries around the globe.

From temperature to standard N
This is one I’ve been thinking about for a long time, and have discussed with many turf managers, but I don’t think I’ve explained
it on the blog yet. So here goes.1 This is what I call the turfgrass
Genki Level.

Background, or why I think this is usefulSometimes I get questions like this:“For someone that would like to begin utilizing Growth Potential
with more consistency, what are you general guidelines for Nitrogen applications for Ultradwarf greens? What would those same
recommendations be for Bermudagrass grown on Tees/Fairways?
I’ve seen a reference of .8 lbs N per month when max GP. Is that agood number on greens or is that too high? I know that I can always
raise or lower based on what I’m seeing or what golfers are expectingwith speeds, but just curious about a starting point.”

To answer that question, I want to give some idea about not only
the standard amount for max GP, but also I want to express what
turf managers are doing at any given time. The ratio of what is
applied, compared to the standard amount, is what I call the Genki
Level.
And I often want to discuss the intensity of pushing the grass
to grow at a given time, or the intensity of pulling on the reins byrestricting N, and to do that, I find it useful to communicate interms of the genki level.
Here’s an excerpt from an email I sent last year, explaining this:“About the ‘predicted’ [or standard] amount, that is somewhat arbitrary. That’s what I think is about normal for the way bentgrass istypically managed today. The predicted amount can flip between N
supply as fertilizer, and N use by the grass. Basically I tend to thinkof the predicted amount as what I expect for use, and if the soil will
supply that amount, then the amount as fertilizer can be negligible.
That’s something to do, probably, with why your fairways in August
didn’t require N.

This section was publishedas part 1 of the series at1

https://www.asianturfgrass.com/
2019-02-03-the-turfgrass-genki-level-part1/

the turfgrass genki level2

Also related to the predicted amount is the relationship or ratio between the N supply and the predicted amount. This seems intuitive
to me, but I have a feeling that for most golf course superintendents
it would be confusing as hell—at least at first.
The idea is that there is a predicted amount that is pretty normal.
The amount you supply, in relation to the predicted amount, issomething that I don’t think there is a word for. I want to call it‘genki level’—genki being a Japanese word meaning good or healthyor how are you—or GL which could also be growth level for those
who prefer a more straightforward description.”

Getting started, considering 3 locations
I used the Dark Sky2 API to get daily temperature data from each
day in 2018 from three locations. That is, I took the latitude andlongitude of Hazeltine National GC in Chaska, Minnesota (creeping
bentgrass); Keya GC in Itoshima, Japan (manilagrass); and Van Tri
GC in Hanoi, Vietnam (seashore paspalum); I then obtained theobserved weather conditions from those locations.

Those are the daily high and low temperature data. From those
I calculated the daily average temperature, and from that one cancalculate the temperature-based turfgrass growth potential (GP) of
PACE Turf.3
Temperatures are useful. So is the GP, to quickly express on ascale of 0 to 1 the relative distance between the actual temperatureand the optimum temperature for shoot growth.
The GP makes it easy to compare locations. And it is also straightforward to make an estimate of growth and N use. By multiplying
a maximum amount of N by the GP, one gets an expected N use.4
Based on the way creeping bentgrass, manilagrass, and seashore
paspalum are managed as fine turfgrass today, I like to use a standard maximum of 3 g N m-2 month-1 .
I think it is useful to use the same standard N for the calculations,and then to express differences in the way turf is managed as the
genki level. That makes it easy to compare the relative amountof pushing the grass, or pulling on the grass, between different

2

https://darksky.net/poweredby/

Figure 1: Temperature at three locations in 2018.

W. Gelernter and L. J. Stowell. Improved overseeding programs: 1. therole of weather. Golf Course Management, 73(3):108–113, 2005. URL
3

http://tic.msu.edu/tgif/flink?
recno=102720

Micah S. Woods. Using temperature
to predict turfgrass growth potential(GP) and to estimate turfgrass nitrogenuse. Technical report, Asian TurfgrassCenter, 2013. URL http://www.files.
4

asianturfgrass.com/201306_growth_potential.pdf

the turfgrass genki level3

Figure 2: Temperature-based growthpotential at three locations.

Figure 3: Temperature-based standard
N at three locations.

the turfgrass genki levelseasons at the same location, or between different locations.
I’ve shown here how the temperature can be expressed as a
GP and how that GP can be expressed as a standard amount of N.
In the next sections, I’ll show the genki level and how much thegrass actually did grow. And I’ll relate this to the turfgrass speedo5
explained by Jason Haines.

5

4

Jason wrote about the speedo athttps://www.turfhacker.com/2018/12/turfgrass-speedo.html

More reading
If you just can’t get enough of this stuff, or want more details andexamples about these type of calculations, please have a look at:• Using temperature to predict turfgrass growth potential and to
estimate turfgrass nitrogen use, http://www.files.asianturfgrass.
com/201306_growth_potential.pdf• Nutrient requirements of tropical turfgrass, http://www.files.
asianturfgrass.com/20130311_woods_handout_nutrient_requirements_tropical_turfgrass.pdf• What fertilizer should I use?, http://www.files.asianturfgrass.
com/20130313_woods_handout_fertilizer_choice.pdf• Turfgrass speedo, https://www.turfhacker.com/2018/12/
turfgrass-speedo.html• A Short Grammar of Greenkeeping, https://leanpub.com/short_grammar_of_greenkeeping

Showing N applied in relation to standard N
I showed how one can go from temperature to a temperaturebased growth potential to a standard N amount.
By looking at the actual N applied, and comparing that amountto the standard N for any location, one gets what I call the genki
level.6
If less N is applied than the standard amount, the GL will be lessthan 1 (Figure 4). If more N is applied than the standard amount,the GL will be more than 1. The GL provides an indication of:• how much the grass is being pushed to grow• how much one is withholding N at a time when the grass has ahigh potential to use N• how that pushing and withholding varies through the year, orfrom site to site
Let’s look in a little more detail at the GL development at Van Tri
GC in Hanoi (Figure 5). Van Tri is wall-to-wall seashore paspalum.

This is a way to make site specificplans, and site to site comparisons, in astandardized way.
6the turfgrass genki level

Figure 4: Genki Level in 2018 at threelocations.

One can start with the temperatures, then work through to the
GL as shown in Figure 6. During the winter months, more N is applied to maintain colour and to try to minimize dollar spot damage.
What about during the summer months? Why is there sometimes a high GL then too, and an annual GL of 1.3? Much of thiscomes down to management style and grass conditions at the time
(Figure 7). And I think there is a relation to grass species too, in thiscase. Seashore paspalum gets overrun in this climate by Cynodon
and sometimes even Zoysia. In order to minimize problems withthose invading species, and to minimize problems with weeds ingeneral, seashore paspalum is often maintained at a relatively rapid
growth rate.

Figure 5: Sea Isle 2000 seashore paspalum on the 2nd green at Van Tri GC
during December.

5the turfgrass genki level

Figure 6: The progression fromtemperature to genki level for the
Van Tri location, by calculating thetemperature-based growth potential,from that a standard N, and then comparing the actual N to the standard.

6the turfgrass genki level

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Turf growth response measured by clippings
I’ve explained how the ratio of N applied to standard N gives
an indication of how much one is pushing the grass to grow. I callthat the genki level (GL).
How much the grass really does grow can be measured by theclipping volume7 . With the GL as shown in Figure 4 in 2018, andthe temperatures and GP as shown in Figures 1 and 2, Figure 8
shows the clipping volume at these locations in 2018.

By looking at the GL and at the clipping volume, one can see
how much one was pushing the grass to grow at any time, and thencan see how the grass responded.
Jason Haines has suggested another way of looking at this. He
calls this the turfgrass speedo and it is the actual clipping volume
divided by the maximum clipping volume that one would everwant to see, with that maximum multiplied by the growth potential.
I took the clipping volume data from these three locations in2018 and calculated a turfgrass speedo (Figure 9) for each monthin which the greens were mown. For Keya I used a monthly maximum of 600 mL/m2 , for Hazeltine I used 500, and at Van Tri I used
2,000.
The speedo is of course quite sensitive to the value that one
has set as the maximum for that location. I expect that the ideal
maximum for any location will vary depending on traffic, grass
type, turf conditions at the time, desired playability, and so on.

A normalized comparison of N fertilizer to growth rate
The amount of nitrogen (N) supplied over a certain time
duration, compared to a standard amount, is what I call the genki

Figure 7: Sea Isle 2000 seashore paspalum on the 12th green at Van Tri GC
during May.
7
See my book, One Bucket at a Time,for more details of clipping volume.
You’ll find the book at https://www.

asianturfgrass.com/buckets/

Figure 8: Clipping volume at threelocations in 2018.

the turfgrass genki level

Figure 9: Turfgrass speedo at threelocations in 2018.

level (GL). And the amount of clippings harvested over a certain
time duration, compared to a standard amount, is what Jason
Haines calls the turfgrass speedo.
In this discussion, I’ve been working with monthly time durations.
What if one compares the genki level to the turfgrass speedo ona scatterplot? The result is an interesting comparison of how muchthe grass was supplied with N, plotted simultaneously with theactual growth, with both adjusted for the season of the year. That’s
what I mean by a normalized comparison.
Let’s look at this for korai (Zoysia matrella) putting greens at Keya
GC in Fukuoka, Japan. In the winter, this warm-season grass isn’t
growing (Figure 10), and the clipping volume during January 2018
was 0, because the greens weren’t mown.
When the clipping volume is 0, the turfgrass speedo is 0. And no
N was applied in January 2018, so that gives a GL of 0 too.

Figure 10: Korai greens at Keya GC
don’t grow in the winter; the clipping
volume is 0.

Figure 11: Genki level and turfgrass
speedo for a month at Keya GC with
no N fertilizer and no growth.

8the turfgrass genki level

When the GL is the same as the speedo, the point will fall on
the 1:1 line, as shown in Figure 11. What if the point would fall tothe left of (or above) the 1:1 line? That means that the growth forthat time duration is more than would have been expected, given
the amount of N supplied. And if the point falls to the right of (orbelow) the 1:1 line? That means that one is pushing the grass with
N fertilizer during that time duration but the growth response isn’t
happening yet.
Figure 12 shows this for January, August, and October 2018.
Figure 12: Genki level and turfgrass
speedo for three months at Keya GC
with varying N supply and varying
growth.

In August, the point falls to the left of the 1:1 line, and in October, the point falls to the right of it. What’s going on here?
During August (Figure 13), the temperatures at Keya GC are hot,and there is a lot of N mineralization. In addition to that, warmseason grass grows a lot when the temperatures are hot. So the
speedo is more than the GL.
But by October, the GL is now more than the speedo. That indicates that the grass is being pushed to grow but isn’t responding
during that same time duration. The temperatures are getting coolin October; the growth of korai slows dramatically by October inFukuoka but by supplying N the green color of the turf8 can beretained into the winter.
In Figure 14, I show all the months in which the greens were
mown, and I show also for Hazeltine National GC and for Van Tri
GC. I’ve also normalized this in one more way; I’ve set the maximum growth for the speedo at 600 mL m-2 month-1 for all thelocations.
I find this to be a useful way to think of, and to visualize, theturfgrass response to the N supplied. I also find this especially useful in comparing how grass is managed at different locations, andFigure 13: The 18th green at Keya GC
in August 2018. The turfgrass speedo
was 0.63 during that month eventhough the GL was 0.19.

Keya GC greenkeeper Andrew
McDaniel shared photos of the colorin October in this tweet, https://8

twitter.com/drumcturf/status/
790395640932995073, writing “These

Korai greens are ready to ride out thefall season into winter.

Incidentally, there is an interestingarticle about Andrew and his workin Japan, orginally published in Golf
Digest Japan, posted in English at
http://www.files.asianturfgrass.
com/andrew_digest_2018.html

9the turfgrass genki level

Figure 14: Relationship between
turfgrass speedo and genki level forthree locations in 2018.

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the turfgrass genki level

that’s another reason I’ve set the maximum N and the maximum
growth at the same value for the speedo and GL calculations.
Is there any take-home message from this?9 I expect these things:
1. if one is consistently to the left of the 1:1 line, either the soil is
supplying plenty of N, or the grass is going to need more N
sometime in the future
2. if one is consistently to the right of the 1:1 line, you can probably
cut back on the N applications
3. if the speedo is almost always more than 1, I’d think about reducing N even further, restricting water supply, or increasing
growth regulators
4. if the speedo is almost always less than 1, I’d think about growing the grass a little more at some times of the year by doing the
opposite of the items listed in point 3

What’s real, what’s not, & the simplicity of thisIn this pamphlet, I’ve showed how one can start with temperatures and go all the way to a standardized comparison of growth inresponse to nitrogen supply. In this one, I want to emphasize whichof these are real, which aren’t real but are useful, and to make anargument that this is a lot easier than it might seem.
We’ve looked at temperatures and standard N amounts given
those temperatures. From that, we can look at the actual N, andrelating that to the standard N we get the genki level. Then we
looked at the grass response to the temperatures, and to the GL,
by studying the clipping volume. And in the previous section thenitrogen fertilizer and the clippings were compared, both adjusted
for temperature.

What is real
The only real things in all of this are:• the temperatures• the nitrogen applications• the grass clippings

Not real, but useful
The things that aren’t real, but are calculated values that I finduseful are:• the temperature based growth potential (GP)• the standard N based on GP

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I’m generalizing in this list, withthe take-home messages being thosethat may apply to facilities with usual
traffic and consequently standard
growth rates. The point of all this isthat these numbers can be useful as away to fine tune the growth at one’s
facility, and as a way to compare theconditions one has produced, and how
those conditions were produced, withother facilities. And because the GL
and the speedo are normalized bytemperature, I could compare Bangkok
to Boston, or Sydney to San Francisco,without much trouble.
9the turfgrass genki level12• the actual N compared to standard N, or genki level (GL)• the standard GP-based clipping amount• the actual clippings compared to standard clippings—the speedo• the ratio of GL to speedo
How are these useful?
First, for any location, these calculations provide an easy way to
optimize conditions. This happens by considering and then adjusting the growth rate of the grass to produce the desired conditions.
Looking backward, evaluating the present, and planning ahead,these calculated values are easy to use as a way to make improvements. Or, if the grass is already perfect, to keep it that way whentemperatures are different.
Second, for any location, these calculations provide an easy way
to integrate (or get started with) new maintenance strategies thathave been learned from other turf managers.
I’ve written more about this in the Short Grammar of Greenkeeping.10

The simplicity of thisIt might seem complicated, but one has this information already.
All the charts and calculated values happen instantly in the background; all this can be done automatically by a computer.
Every turf manager has the temperatures and forecast temperatures. Every professional turf manager knows the N that has been
applied. That’s all one needs to use the GL. The calculations are all
made by the computer.
To look at the growth and use the speedo, one needs some measurement of growth. And that’s pretty easy to get. I’ve written
about that in One Bucket at a Time.11

An example from start to finish
I have temperature and N application and clipping volume from
Hazeltine National GC, so I’ll show how this progresses. One caninfer how the information might be useful.
Many turf managers will have data from an onsite weather station or will get temperatures from another local source. I’ve used
Dark Sky12 to get temperature data (Figure 15) for the latitude andlongitude coordinates of Hazeltine National Golf Club in 2018.
Those temperatures are something real. I then transform themto something that isn’t real, but is useful. That is the temperaturebased growth potential (GP) of PACE Turf13 . The GP is useful in a
lot of ways; in Figure 16 it is shown as a visual representation of thegrowing season for cool-season turf at that location in 2018.
I then make a further calculation to show in Figure 17, on amonthly basis, what I call the standard N. That is based on GP anda maximum monthly N for bentgrass of 3 g N m-2 .

10

You can get a copy of this book at

https://leanpub.com/short_grammar_
of_greenkeeping.

This book about clipping
volume is available at https:
11//www.asianturfgrass.com/buckets/.

12

https://darksky.net/poweredby/

13

https://www.paceturf.org/

the turfgrass genki level

13

Figure 15: Temperature data for thelocation of Hazeltine National Golf
Club in 2018.

Figure 16: Temperature data for the location of Hazeltine National Golf Clubin 2018, converted to temperaturebased growth potential.

the turfgrass genki level

The nitrogen applied each month is something real; I’m representing it in Figure 18 as the genki level—that is the actual N
supplied divided by the standard N.
The genki level corrects for the expected or potential growththat can occur at any location because of temperature. When thegrass grows more, it uses more nutrients. When the grass grows
less, it uses less nutrients. By using the genki level to look at N
applied, one gets an idea of how much the grass was being pushed
or starved of fertilizer N at any particular time.
A note here: I made the calculations here monthly. One canset it up to look at these daily, weekly, or on any time interval of
convenience.
The grass growth response can be monitored by the clipping
volume. Now we are looking at something real again. Temperatureis real. The actual N applied is real. And the clipping volume in
Figure 19 is real.
I’m going to make another correction to the clipping volume
data, however, by converting it to a turfgrass speedo. For Figure 20,
I’m using a maximum volume of 600 ml m-2 month-1 , and thencalculating the speedo as the actual clipping volume divided by the
product of the GP and 600 mL.
What good does that do? Just like the genki level adjusts the N
fertilizer to the potential for the grass to grow, so the speedo adjusts
the actual growth to the temperature-adjusted expected growth.
Finally, I compare the genki level to the speedo in Figure 21.
These are two real things—the N applied and the clippings collected—
adjusted by another real thing, the temperature at that location.

14

Figure 17: The standard N for the location of Hazeltine National Golf Clubin 2018, derived from temperature andgrowth potential.

the turfgrass genki level

15

Figure 18: Genki level for Hazeltine
National Golf Club in 2018.

Figure 19: Clipping volume fromputting greens at Hazeltine National
Golf Club in 2018.

the turfgrass genki level

16

Figure 20: Turfgrass speedo at Hazeltine National Golf Club in 2018.

Figure 21: The turfgrass speedo compared to the genki level at Hazeltine
National Golf Club in 2018.

the turfgrass genki level

Turfgrass perfect and want to do exactly the same as last year?
Then do the same, adjusting for this year’s forecast temperatures.
See some areas that can be improved? Consider how adjusting the
growth and the timing of the growth might move the turf closer
to the desired conditions. Talked with a friend from a neighboringstate or from another part of the world, and learned how their
management is producing great results at a certain growth rate or
timing or fertilizer rate? Easily apply the same processes at yourfacility, adjusted for the growing conditions at your site.
And if you have read all the way to the end of this, don’t likenumbers, and are happy managing by feel, then thank you forreading. That’s a fine way to manage turf too.

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