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August 2014

More about the measurement of grass clippings

Pg (1)
2 liters of clippings from the putting green

One can measure the volume of clippings collected when mowing greens through the simple process of bringing along a bucket to empty the clippings into.

This technique is used at Keya GC in Fukuoka, the host club for this week's KBC Augusta tournament. The greensmowers bring along a bucket and take note of the volume of clippings collected from each green.

Mowing the practice putting greens at Keya GC

In a previous post, I mentioned some of the ways that this information can be put to use. Here at Keya, the target for tournament week was to be at less than 10 L per green. During the 2013 tournament, the clipping volume averaged 11.8 L per green during tournament week, and 5.3 L per green in the week immediately after tournament week. The course superintendent, Andrew McDaniel, thought that putting surfaces for the 2014 tournament would be best if the clipping volume were slightly less than in 2013.

The clipping volume is collected year round, and from most of the greens. I've taken a subset of the 2014 data and plotted it for the month of August, with the average clipping volume from greens 1, 2, and 4, just to show how the yield has been this month, through this morning, the 2nd round of the tournament.


It looks like the clipping yield is close to the target range. By tracking the amount of clippings, one can adjust nitrogen rate, growth regulator applications, and mowing height and amount of mowing in order to modify the amount of clippings.

The use (or not) of brushes, or groomers, or the effects of various other maintenance practices can be evaluated when the clipping volume data are available. The Shibaura G-EXE22 mowers used on the greens can be fitted with this brush.

Brush fitted between the front roller and the bedknife on the Shibaura G-EXE22

Andrew found that use of the brush increased the number of clippings by a factor of 2. During the tournament, the brushes are not being used, but in the lead up to the tournament, the brushes were used to increase the amount of clippings and help create the desired surfaces.

View from behind the 14th green at Keya GC

Now, during tournament week, the korai (Zoysia matrella) greens at Keya GC are growing at just the desired rate, and the mowers are removing the targeted amount of clippings. It doesn't take much extra time to collect this information, and having a time series of these clipping volume data can help a turf manager make decisions about the adjustments to make in green maintenance.

Korai green surface at Keya GC

It cures fairy ring and prevents fungal pathogens: an anecdote about ammonium sulfate

Fairy ring symptoms, 8 green, August 2013

Last year, at the KBC Augusta golf tournament, there was some type 2 fairy ring on the 8th green of host Keya Golf Club.

I'm back at Keya one year later, and now those symptoms are completely absent.

No fairy ring symptoms, 8 green, August 2014

These rings were also found, prominently displayed right in front of the clubhouse, on one of the practice putting greens.

Fairy ring symptoms, putting green, August 2013

One year later, the fairy ring is gone. 

No fairy ring symptoms, putting green, August 2014

To what can we attribute this remarkable transformation? I asked Andrew McDaniel, the golf course superintendent at Keya, if he applied any fungicides for the control of these rings. He didn't.

No fairy ring symptoms, putting green, August 2014

If it isn't fungicides that controlled it, then it must be something else in the products he applies. I checked the Keya GC turfgrass maintenance page on Facebook, and I learned that these greens receive only ammonium sulfate, micronutrients, and sometimes Primo Maxx.

This is remarkable! In just one year, the fairy ring has been eliminated. Furthermore, there has never been Curvularia (a notorious disease of korai, which is especially susceptible) on these greens since this ammonium sulfate has been used, and there has been no dollar spot, pythium, or brown patch either. 

It seems pretty clear that this simple fertilizer program based on small amounts of ammonium sulfate (less than 10 g N m-2 so far this year) and some micronutrients, with judicious applications of Primo Maxx, has cured the fairy ring (at least for the moment) and it has also prevented a number of other diseases. Whether this is due to a direct effect on the pathogens, or whether the improvement to plant health from this ammonium sulfate is making the plant strong enough to withstand any attack, I can't say. There may be some additional benefit from the low carbon and low calcium characteristics of this management approach.

I wrote the above in jest. Yes, that is the fertilizer used. And yes, there really was a lot of fairy ring last year, and none this year. And yes, it might be possible that the fertilizer is the cure, or the no calcium and no carbon approach to turf management is the cure, but there are a lot of other things that could have played a role as well.

That's a problem with anecdotes – they might seem persuasive at first glance, especially if one is already inclined to think about things in a certain way, but upon closer inspection one realizes that a number of other things could explain the same phenomenon. 

Superintendent Andrew McDaniel on the 8th green in August 2014 - note the absence of fairy rings

Fortunately, we have the scientific method, which involves forming a hypothesis and collecting some data to test if that hypothesis is reasonably correct. Here's a fun introduction to that from Richard Feynman.

When there are products or practices that are promoted primarily by anecdote, and have little supporting evidence, it makes me skeptical that they are necessary. Why? Because it is easy to collect data, and to use control plots, and careful monitoring of results, to determine if something works and to estimate the magnitude of the effect. That is the main work of scientists, but it is not limited to that profession – anyone can do this.

This has some bearing on biostimulants and compost tea as additions to turfgrass maintenance programs, as per this recent discussion. When there is a lot of anecdote and little in the way of data, I'm naturally quite skeptical. And I'm skeptical for the reason that it is so easy to collect data. So my expectation is that if there is a conspicuous lack of data, then someone must have tried to collect data on a product, and was not able to obtain data with a convincing result. 

Here are a couple good articles on these topics:

Biological pest control: a realistic outlook

Testing Products and Practices: a guide for golf course superintendents

The good thing about science is one can make hypotheses and then attempt to prove them wrong. In that way we make corrections, and improve our understanding of the world. 

Keya GC putting green, August 2014

Measuring and tracking grass clippings

Many golf courses in Japan track the volume of clippings mown off putting greens using this simple technique. A plastic bucket is brought along on the mowing runs, the clippings are placed in the bucket, the bucket is shaken to allow the clippings to settle, and the volume of the clippings is recorded.


This information can be useful to check, track, and improve the management of putting greens, For example, the data can be used to:

  • ensure that all mowers are set up the same way
  • measure the effect of fertilizer applications
  • measure the influence of growth regulators
  • evaluate the effect of weather and maintenance practices on growth
  • track clipping yield for special events


Andrew McDaniel is the golf course superintendent at Keya GC in Fukuoka, where the Japan Golf Tour Organization (JGTO) holds the KBC Augusta tournament. Leading up to the tournament, the clipping volume of the korai (Zoysia matrella) greens was generally more than 20 L per day per green with a single cut. Today, on the Wednesday of tournament week, a double cut of the greens is collecting about 5 L of clippings per green. The progression to the tournament target clipping volume has been monitored carefully.


He also used brushes on the mowers in the lead up to the tournament. When two mowers were used on the same green, each mowing the green once, the mower with the brush collected about twice as many clippings as the mower without the brush. 

For an even more detailed look at clipping production over time, and different ways I've seen it measured, see my report on clipping yield from putting greens.

More about metrics: turf in 2 dimensions

I've written about the seductive attractions of metric units and how facility with those units can make turfgrass management easier. I want to explain this a bit more, especially as it is related to fertilizer and to water, first discussing 2 dimensional surfaces. 

Last week in Macao (presentation slides and handouts here) this very subject came up. I was discussing turfgrass fertilizer, which is really simple, largely because turf surfaces can be simplified to a 2 dimensional area, square meters (m2) or square feet (ft2) or whatever. 

But with landscapes, as we saw at the interior gardens (above) and outdoor gardens and golf course (below) at the Venetian Macao, it is very much an irregular and inconsistent 3 dimensional space. 


These landscapes are impressive, but they resist simplification. When applying fertilizer, for example, should we apply it on a per plant basis? Or on a size of plant basis? Or on a gound area basis? Plus there are so many different species, each, presumably, with some different nutrient requirements.

With turfgrass surfaces, we don't really have to consider those complications. Compared to landscape plants, turfgrass surfaces are simple. No matter where we are in the world, and no matter what grass type is being grown, we can express a number of important metrics in 2 dimensional terms.


I like to use one square meter (1 m2) as the base unit in 2 dimensional space. That is, I take a turf surface, such as the zoysia putting green pictured below, and consider it in terms of length (1 dimension) and width (1 dimension). Combining the length and width, we have 2 dimensions, and can consider the flat surface with those dimensions. 


This goes for any turfgrass surface. Golf course putting greens, lawns, football fields – we often ignore the rootzone, and ignore the volume of the aboveground plant parts, and simply consider the flat 2 dimensional area.


We then express inputs to the turfgrass surface in terms of mass or volume as applied to a 2 dimensional space. For example, the annual nitrogen amount supplied to a turfgrass area might be 10 g N m-2, which is equivalent to 2 lbs N 1000 ft-2. We would be thinking of how much mass of something is applied per area. Turf is irrelevant here, because we could apply a mass of something to a certain area of parking lot, or of lawn, or of bare soil. It is just mass per area.

That's easy, and we use those units all the time. Irrigation can be thought of in the same way. I often think of water in these terms. The consumptive water use of the grass is the evapotranspiration. In general one needs to supply something similar to the consumptive water use in order to keep grass actively growing. Water use (evapotranspiration) is expressed as a depth (1 dimension), just as precipitation is expressed as a depth (mm). We now have 3 dimensions, because we have a depth applied to an area, but with the metric system this is pretty easy to convert back to a mass or volume per area. No calculator required.


Let's say we have ET of 4 mm, and we want to supply that as irrigation. 4 mm equals 4 L spread across 1 m2, so for a 500 m2 area, we would need 2000 L of water.

For topdressing sand, we could do the same type of expression. Topdressing sand may be applied at 100 g m-2. For a 500 m2 area, that would require 50 kg of sand.


Fertilizer, water, sand – applied as a mass or volume to a 2 dimensional area – this isn't anything new. 

But there is more to it than this, for the turf in reality is growing in a 3 dimensional space. Being able to convert the amount applied at the surface into units that express changes in the 3 dimensional space of the rootzone is quite useful. Being able to relate changes in the rootzone to simple units of how things are usually applied at the surface is also quite useful. Coming up, I'll write about turf in 3 dimensions, and explain how I go about making some of these conversions on the fly, and why I find the metric system so useful in this regard. 

On day length, growth potential, and fertilizer estimates

The temperature-based turfgrass growth potential (GP) was developed by Wendy Gelernter and Larry Stowell at PACE Turf. Based on only one variable – the actual temperature – one can use the GP equation (below) to produce a number between 0 and 1.

\[GP = e^{-0.5(\frac{t-t_o}{var})^2}\]


GP is growth potential, a value from 0 to 1
e is the base of the natural logarithm, approximately 2.71828
t is the actual mean temperature
to is the optimum temperature, usually set at 20°C for C3 grass, 31°C for C4 grass
var is the variance which adjusts the shape of the curve, 5.5 for C3 species and 7 for C4 species when using °C.

If the GP is close to 1, then we can think of the growth potential as being high, because the actual temperature is close to the optimum temperature for growth. If the GP is closer to 0, then we can think of the growth potential as being low, because the actual temperature will be much colder or much hotter than the optimum temperature.

Temperature is not the only thing that influences turfgrass growth, however. The four main factors that influence growth are temperature, photosynthetically available light, plant water status, and leaf nitrogen content. For more about this, especially as it relates to the growth of warm-season (C4) grass, see A New Way of Looking at the Weather.

Turfgrass managers are able to modify the plant water status and the leaf nitrogen content, so the two independent and uncontrollable growth factors are temperature and light. The GP equation only accounts for temperature. Would it be improved if a correction for daylength, or shade, or light were included?

This question was recently posed, in this conversation on Twitter.

I default to a rather extended answer, because there is not a clear answer to this, but it is something I have considered, and my preference at this time is to ignore light and day length when it comes to GP values. Here's why.

1. The GP is not reality. It is only a number that serves as an index of the potential to grow based on temperature. This analysis of clipping yield at various levels of GP shows that there is a general relationship between GP and yield, but not an exact one.

Clipping yield from korai putting greens on a golf course in Japan from mid 2013 to early 2014

2. The GP equation is simple. Providing a numerical value of potential to grow, based only on temperature, can be practically useful in many ways, even though this number is not an exact description of how the grass will actually grow. Because the GP as it is does not predict growth exactly, and is simply an index of potential to grow, I think adding on layers of additional data for day length and/or photosynthetically available light risk complicating this by assigning too much value to the GP number, even though the growth may not exactly match the GP.

3. When I work with GP, my preference is to keep it as simple as possible, as long as the GP values for a particular site match the reality of observed turfgrass growth. GP is only useful when it somewhat approximates reality, so if day length adjustments, or adjustments for photosynthetic radiation, make the GP a more accurate representation of reality at a particular site, then I would look on such adjustments as a good thing.

In response to questions about possible increased fertilizer requirements at high latitudes due to increased day lengths, I have made some comparisons, and I haven't seen that extended day lengths will necessarily correspond with more light energy for growth. 

4. If we look, for example, at Malaga and London specifically, along with some other cities from the northern hemisphere, the estimated daily light integral plotted against day length on 15 June looks like this.

That is, even though the day is longer at London in mid-June, because it is at a higher latitude than Malaga, there is still a greater amount of photosynthetic light at Malaga than at London. Why might this be? It is related to the amount of extraterrestrial radiation at any given latitude, combined with the effect of clouds. On an average June day in London, there will be 6.8 hours of bright sunshine (defined as light > 120 W/m2) on a day with 16.3 hours. At Malaga, even though June 15 has a shorter day length than London, with only 14.5 hours, 10.5 of those hours on an average day will be bright sunshine.

With warm-season (C4) grasses we can make the assumption that the grass can use all of the DLI. With cool-season (C3) grasses, that won't be the case when the light is at its greatest intensity.

I have tried to estimate this by taking a maximum value of 1000 micromoles of light per m2 per second, for each second of day length, and expressing the estimated DLI as a fraction of that. This chart shows that at Malaga, the amount of light supplied on an average day on 15 June is equal to the maximum amount we expect C3 grass to use. At London, even though the day is longer, it appears that on an average day there is less light supplied than the grass can use.

Based on these calculations for June, I don't see a reason to adjust the expected nitrogen use of turf at London to be higher based on day length.

I also looked at this for December, in this chart for estimated DLI on 15 December and this chart for the fraction of usable light that is supplied on average.


In this case, there are again differences in DLI and day length. At Malaga, where there had been nearly 100% of the light that C3 grass could potentially use on 15 June, the amount of light supplied on a typical 15 December day is only 50% of that the grass could use.

But for many of these cities, on 15 December, the amount of photosynthetic light is irrelevant, because the temperature is so cold that the grass can't grow. At Milan, for example, the average temperature in mid-December is less than 5°C. When working through these calculations, the temperature will often be the controlling factor.

5. Light does influence the growth, and consequently the nutrient use of grass. In my analyses of this, it seems that temperature plays the controlling role, with light as a secondary factor. I think that this can be accounted for using the GP equation as is, on a site by site basis. For example, at Malaga or Milan or London, one can use the GP to estimate nitrogen requirement as explained in this document.

One only needs to estimate the maximum amount of N that one will use at that location, in the time (day, week, or month) when N use will be at a maximum. The GP can then be used to adjust the N rate over the course of the year. The key is to choose an appropriate maximum N amount for the location, grass species, and soil type. Any light correction can be embedded in the amount of N one chooses as the maximum. My preference is to utilize GP in this way – it is remarkably simple, and provides a good starting template for nutrient requirements.

6. If adjusting by day length or other adjustment to account for light works better at a particular location, then by all means make the adjustment. The objective of the growth potential is to estimate how the grass will actually have the potential to grow at a location. From all the calculations and observations I've made, I'm not convinced that day length or light adjustments improve upon the estimates we can get from temperature alone. Of course, my experience is mostly at latitudes less than 45°, so there may be something I miss at higher latitudes. 

Turfgrass Mystery: the curious case of the cup cutter in the fairway


Some years ago, on a fine December day, I was at this beautiful golf course in southwestern China. The tees, fairways, and greens are creeping bentgrass. From the tee, I had the view above. But when I got to the fairway, I was surprised to look down and see this pattern.


In fact, there were a lot of cup cutter plugs, lined up one by one, on this fairway.


The mystery is this: why are there cup cutter marks in the fairway?

The correct answer was given in quick succession by @GreatManDan and then soon after by @gossturf.

What I found especially interesting was just how many plugs it took to make this repair. The diagonal across the fairway was about 175 yards in length. With each plug 4.25 inches in diameter, that would require 1482 individual plugs to make the repair. 

Presentation slides and handouts from Macau

2014-08-15 16.28.47
I really enjoyed today's meeting of the South China Turf Managers Association (SCTMA) in Macau. There is more to share later, but for now, here are the handouts and slides for the two topics I discussed this afternoon.

First was Measuring Sustainability, in which we discussed simple measurements that can be used at any facility to track relevant inputs.

The second presentation was about nutrient requirements. I explained how the MLSN guidelines can be used as a simple decision making tool.

There are two questions that every turfgrass manager will have when it comes to fertilizer. First, is an element required as fertilizer, or not? Second, if that element is required, how much should be applied? The MLSN guidelines answer both of those questions, for any grass, anywhere. The presentation and associated handout explain how to do this.

After the seminars, we took a tour of the very impressive facilities at The Venetian, then had dinner and lots of turf talk with friends at a poolside reception.


Three of my favorite projects from Beth Guertal's Research Group

Fertilization of bentgrass with commercial foliar products - guertal ats 2010.pdf (page 1 of 10)
I was excited to read the press release from AGIF and GCSAA last week announcing that Beth Guertal will be teaching in September at events in the Philippines and Vietnam. I've always enjoyed studying the research she does, and these seminars are a great opportunity for learning from one of the world's experts on turfgrass management. 

I'm not sure that she will be talking about these particular experiments, but these are three of my favorites (of the many) from her research group.

  1. Fertilization of bentgrass with commercial foliar products: Greenhouse evaluations. "In most cases foliar application of urea was as effective (for N uptake and dry matter yield) as applying any of the commercial materials."
  2. Potassium Movement and Uptake as Affected by Potassium Source and Placement. "Over the 2 year study potassium application had no beneficial effects on turfgrass performance, and acceptable performance was achieved across a wide gradient of K content in soil and leaf tissue. Regardless of soil test K level, no deficiency symptoms were observed."
  3. Fan and syringe application for cooling bentgrass greens. "In general, reductions in the maximum observed temperature occurred in the following order: fan plus syringing, fan only, syringe only, and, no fan/no syringe."

Monthly Turfgrass Roundup: July 2014

If you missed them, these articles and links from the past month may be of interest to turfgrass managers in Asia:

Part 2 of the Golf Club Atlas interview with Don Mahaffey.

Glen Obear's paper on iron-cemeted layers on putting greens is available for free download.

Use pH and organic matter to estimate CEC of sand rootzones.

Potassium in the soil declines rapidly in some sand rootzones.

Growth potential article in GCM China.

What's the right optimum temperature for growth potential?

Superintendents discuss their involvement with the Global Soil Survey.

New video about the Park Grass experiment.

Carpetgrass part 1: underused and unappreciated.

Carpetgrass part 2: ugly duckling, or swan?

Adding potassium didn't improve drought resistance of warm-season grass.

These turf management videos from PACE Turf.

Penn State's guide to turfgrass fertilization.

Bleached bands on Zoysia japonica at Okayama

What's the cause of bleached bands on Zoysia japonica?

Clover. Disappeared. With no herbicide. Jason Haines noticed something crazy.

Adding potassium increased incidence of pink snow mold.

For more about turfgrass management in Asia, browse articles available for download on the ATC Turfgrass Information page, subscribe to this blog by e-mail or with an RSS reader - I use Feedly, or follow @asianturfgrass on Twitter. Link and article roundups from previous months can be seen here.

Turfgrass Mystery: the tee with the solitary stripe

Late spring in the Yangtze River Delta. A time of glorious weather before the sultry summer. Tea in classical gardens. Flowering trees have bloomed, and are now in full leaf. On the golf course, grasses are growing a little more rapidly day by day.

That sets the scene for this mystery. A bermudagrass tee, in late spring, in the Yangtze River Delta of East China. In the previous 2 weeks, the lowest temperature was 10°C, and the highest was 31°C.


On the tee, a strip of green. Here is a look from another angle.


A closer look at the turf in the green stripe is here.


And this is what the turf looked like outside of the green stripe.


The mystery is this: what caused the green stripe on this tee? 

Congratulations to Jason Goss who got this one exactly correct:

I think the key for this was recognizing the season and climate. With that type of climate, it is common to overseed bermudagrass tees. But one wants to ensure the bermudagrass can grow with no competition from perennial ryegrass for more than 100 days in the summer. That is necessary to keep healthy bermudagrass. Thus, on this high traffic tee, Monument herbicide (trifloxysulfuron) was used to remove the ryegrass, which will allow the bermudagrass to grow with no competition through late spring and all through the summer.

For more about this technique, see the Removing Overseeded Perennial Ryegrass from Bermudagrass Turf fact sheet from the University of Tennessee. 

Partial credit for a correct answer to @GreatManDan and @PenderSuper, who identified the herbicide skip and ryegrass involvement.

Thanks to everyone who sent their answers. For other turfgrass mysteries, click here.