Bermuda

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.

Fort_smith_tokyo_polygon

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.

2016_gdd_batesville_tokyo

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.

2016_dli_batesville_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.

Definitions:

  • 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.

Assumptions:

  • 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:


New paper on variability of hybrid bermudagrass used on putting greens

If you work with warm-season grasses, you will want to have a look at this new paper by Reasor et al. on the variability of hybrid bermudagrasses used on putting greens.

Selection_083

Ever see anything like this? Off-types growing in a green? Wondered if the off-types are contamination by a completely different grass, or if the grass has mutated?

Ot

This paper explains what can happen, what has happened, and why. Plus it has a historical review of these hybrid bermudagrasses used on greens. Find out where they came from and how the grasses are related.

ReasorSometimes I write about papers that are behind a paywall and most people can't read (or at least don't want to pay the high fees to purchase). I'm glad there won't be that problem with this article, as Reasor et al. have published this open access so everyone can read it.

I've just spent a couple weeks with the lead author Eric Reasor (pictured at right in Japan) collecting data from bermudagrass putting greens in Asia.

He's been doing a lot of interesting research about ultradwarf bermudagrass, off-types within those grasses, and the management of putting greens to minimize problems with off-types. Watch out for more interesting research from him on this topic.

 


Another interesting technique to modify fairway conditions

I've seen introduction of seashore paspalum to bermudagrass, and manilagrass to bermudagrass, by hand planting the introduced species into slices cut into the exisiting turf. This post shows seashore paspalum planted into a bermudagrass fairway using that technique.

I've also seen resodding to convert to a different grass, but in a way that doesn't require course closure.

At PGA Catalunya, hybrid bermudagrass was introduced into the creeping bentgrass fairways. These photos show the fairways in 2016, five years after the bermudagrass was added.

Fwy1

The idea was to improve fairway conditions in summer with the bermudagrass, due to the poor irrigation water quality. I've been impressed with the fairway conditions at PGA Catalunya, and also with the technique used to introduce the bermuagrass. These videos of the technique are shared on course superintendent David Bataller's YouTube page.

Fwy

What technique was used at PGA Catalunya?

First, simulated divots were made in the bentgrass fairways using an aerifier fitted with custom "tines".

Second, a rotovator or landscape tiller was used to make a divot mix from certified Tifway 419 sod and sand.

Third, the divots in the bentgrass fairways were filled with the bermudagrass divot mix.

The result is improved fairway performance during the summer, due to the presence of bermudagrass. And with this technique, the improvement was accomplished rapidly, without closing the course, and used a relatively small amount of purchased sod.

Fwy2


Roots, growth potential, and fertilizer

Last month Bhupendra Singh shared this photo of roots on a Tifdwarf putting green in New Delhi.

 

Growing roots! Tifdwarf at Peacock Course Greens, Delhi Golf Club.

A photo posted by Bhupendra Singh (@bhupendra.golf) on

I wondered how the grass had been managed for the past six months.

Here's the high and low temperatures in New Delhi from November 1 until April 9. Delhi_temperatures
Those temperatures, converted to a C4 growth potential (GP), show that the GP was low in winter and approached a maximum as the temperatures warmed in the spring. Delhi_gp
So was there anything extraordinary done to develop roots like this?

Roots1
R4
Bhupendra informs me (and sent along those photos to confirm the results) that the N sources have been ammonium sulfate, urea, and potassium nitrate. The P source is single super phosphate, and the K has come from potassium nitrate and potassium sulfate.

The application rates have roughly tracked the GP.

In the winter, N was applied at an average of 0.5 g N m-2 mo-1. In February and March, as the grass came out of dormancy and the GP approached 1, the N rate has been 3 to 4 g N m-2 mo-1. The P and K are applied in proportion to the amount of N applied, in the approximate ratios used by the grass.

The mower bench setting was 4.25 mm in early April when the photo was taken, with a 3 mm prism reading on the ground.

These are new greens, planted in autumn 2015.

Even for new greens, those are still pretty impressive results. Sure, one doesn't putt on the roots -- what really matters is the surface. But these photos demonstrate that supplying the grass with the nutrients it can use, at the time when net photosynthesis is at its highest, and given water and air in the soil, roots are going to grow.


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.

Result

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.

Tokyo2015

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.


December and January DLI in Everglades City, Florida

I've been reading about the rains and clouds in South Florida and how extraordinary the past couple months have been. I saw these charts from Travis Shaddox, and I wondered what the light would be in photosynthetic units.

I downloaded monthly summary data since March 2007 for Everglades City from the NOAA. I use these data because they include global solar radiation, and I converted from energy units of MJ/m2 to photosynthetic units of mol/m2 using the 2.04 conversion factor of Meek et al.

This shows the average daily light integral (DLI) each month. One can see the seasonal changes, and one can also see that December 2015 had the lowest DLI of any December and that January 2016 had the lowest DLI of any January. I plotted all the data I could get, which is since 2007; I don't know what the values would have been before that. In the past decade, though, these were the lowest.

image from farm2.staticflickr.comLooking just at December and January year by year, January 2016 really stands out for having a low DLI. Blue triangles are December DLIs and red circles are January DLIs; the vertical dashed lines (blue for December, red for January) show the averages prior to Dec 2015 and Jan 2016.

image from farm2.staticflickr.com

In a normal year at Everglades City, January would have more photosynthetic light than December. For seven out of the past eight years, the month of December had a lower DLI than January.  Only 2014 had a lower DLI in January than in December. But January 2016 is a big outlier; not only does January 2016 have the lowest DLI of any of the previous Januaries, but it also has a lower DLI than any of the previous Decembers.


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.