High expectations


I've rarely been so excited to read an article. Last week when I saw Energy use and greenhouse gas emissions from turf management of two Swedish golf courses, by Tidåker et al., I immediately dropped what I was doing and read it.

If you've talked with me about turfgrass management sometime in the past 18 months, our conversation may have touched on differences in energy use, and the difference in carbon emissions, caused by differences in grass selection and maintenance practices. In fact, this is one of the topics Dave Wilber and I discussed as part of our wide-ranging conversation during episode 14 of the Turfgrass Zealot Project. I don't know how to make these calculations yet, but finally with this article I've read something that provides the calculations, and that I can study so I can figure out how to do this myself.

Gelernter et al. wrote in 2014 about quantifying sustainability on golf courses. We suggested measuring and tracking the annual:

  • quantity of fertilizers applied
  • quantity and toxicity of pesticides applied
  • quantity of water used
  • fuel volume
  • labor hours
  • electricity used

One can keep track of those quantities, together with the associated costs, and from that one can check the efficiency of the operation. These quantities also serve as some of the basic data requirements for the GEO OnCourse program.

But the quantities we wrote about in the GCM article are all different: kg of N, kg of fungicide, L of water, L of diesel, kWh of electricity. By expressing all the turf maintenance activities in units of greenhouse gas emissions (expressed as CO2 equivalents) or energy use, one then has a single number for the entire course, or for an area of the course, or per square meter, that can be used to compare to other courses next door or around the world. And the use extends well beyond comparisons to other golf courses; one can use these units to compare the maintenance of a golf course to anything that has greenhouse gas emissions or energy use.

I had high expectations for the article, and I wasn't disappointed. The authors described the fertilizer rates, topdressing rates, water use, mowing frequencies, and much more, for the two courses, and then expressed those units in GHG or energy use. N rates were up to 22 g/m2, as were K rates (I think the rates for golf course turf in Sweden should usually be less than reported in the article -- using precision fertilization, or temperature-based growth potential and MLSN, will lead to lower recommended amounts of fertilizer). Sand topdressing on greens was about 10 mm/year. Irrigation of greens was about 300 mm/year. Mowing of fairways was about 85 times/year, and greens were mown about 180 times/year.


I think this is fascinating because one can consider Sweden to have relatively low inputs. If you're familiar with golf course maintenance in a tropical environment, let's say in Phuket, you might expect fairways to be mown more than 150 times a year, greens more than 300 times, about double the fertilizer, and more than twice the water use. Now imagine what happens when comparing irrigated vs non-irrigated rough? Seashore paspalum wall-to-wall vs. manilagrass? A 60 ha sandcapped golf courses vs. one with drainage and 2 cm of sand topdressing? Overseeded vs. not? The differences in energy use and greenhouse gas emissions will be huge.

What did Tidåker et al. find in their analysis? The entire paper is worth a careful study, but in summary they found mowing was the most energy-consuming activity, and mowing together with the production and application of fertilizers (especially N) contributed the most to greenhouse gas emissions. They suggest:

Appropriate measures for reducing energy use and carbon footprint from lawn management are thus: i) reduced mowing frequency when applicable, ii) investment in electrified machinery, iii) lowering the mineral N fertiliser rate (especially on fairways) and iv) reducing the amount and transport of sand for dressing. Lowering the mineral fertiliser rate is of particular importance, since GHG emissions originate from both the manufacturing phase and from N turnover after application.

Jason Haines has some interesting reads about how turf condition can be improved while at the same time reducing inputs:

Clipping volume variation from green to green

Ryo Ishikawa won the KBC Augusta tournament at Keya GC in Fukuoka this week. Before the tournament started, he was so struck by the green conditions that he wrote about it on his website.


During the tournament, he putted well, with 27 putts Thursday, 26 Friday, 24 Saturday, and 26 Sunday. He had no three putts and 41 one putts on these korai greens during the tournament.

The greenkeeping staff at Keya GC measure the volume of clippings from 12 greens when the greens are mown. I shared some photos of this process, and some of the results during the tournament this year, in these tweets.

I wondered how the clipping volume at Keya GC during the tournament this year compared to other courses. I also wondered if the variation in clipping volume from green to green during the tournament was different from clipping volume variability during a regular week.

To do that, I looked at clipping volume from 7 consecutive days in which greens were mown. Data from Keya during tournament week in 2016 are in the chart below, along with data from the last 7 mowing days at Keya during July 2016, and data from earlier this year from two different courses with cool-season grass.


As far as consistency in the volume of clippings, the tournament data looks impressive. I would expect that this consistency in clipping volume would result in more consistent ball roll on the greens during a tournament compared to everyday play.

I wanted to look also at the variability in clipping volume from green to green on a particular day. Is the variability in clipping volume from green to green lower during the tournament maintenance? To do that, I calculated the coefficient of variation (cv) for these same data. The cv is the standard deviation (σ) divided by the mean (μ).


I like that the cv during the tournament week was on a downward trend. I don't see a huge difference in the overall cv -- the mean cv for these dates is 0.31 for C3 grass #1, 0.37 for C3 grass #2, 0.32 for Keya at KBC Augusta 2016, and 0.32 for Keya during the last 7 mows of July.

One might speculate that greens with the same growing environment and the same soil and the same grass would have a lower cv. The cv shown here may represent some indication of the microclimate effect on growth across a property.

Tournament week clipping volume

The KBC Augusta golf tournament is held the last week of August at Keya Golf Club near Fukuoka. The greens are korai (Zoysia matrella) and when the greens are mown, the volume of clippings is noted.


These data are collected not only during the tournament week, but throughout the year when the greens are mown.


I wrote more about this process in these posts:

Andrew McDaniel, the greenkeeper at Keya GC, shared the clipping yield data with me and I've summarized it in these charts.

The average daily clipping yield, plotted week by week through the year, shows that the grass starts growing at the end of March, reaches a peak in the hottest weather of July and August, before dropping down due to tournament preparations. This reduction in clipping volume is achieved by reducing the N rate, only adding irrigation to prevent dry spots, and applying trinexapac-ethyl.

WeekLooking just at August of 2015, one sees there were 4 days when the greens could not be cut due to heavy rain. One of those days was 25 August, the Tuesday of tournament week, when a typhoon came through. Not surprisingly, the clipping volume is larger on the day after a missed mowing.

AugOnlyThere was a downward trend through August, with the maintenance being done in a way that targets a clipping yield during tournament week of less than 1 liter per 100 m2 of green area.

Looking at clipping volume every day in 2015, it is even more clear when the grass starts growing in the spring, and also that the korai doesn't really grow until after the rainy season, when the temperatures increase. It is only in July and August when the grass is growing quickly. This chart also shows the days during the season when the greens could not be mown.

2015Looking at clipping volume for the 2013, 2014, and 2015 KBC August tournaments, one can see the 2014 and 2015 tournaments had less than 1 liter per 100 m2 from Thursday through Sunday. Based on measurements of green speed and evaluation of ball roll, the goal in 2016 will be to get the clipping yield down to the 1 liter level by the start of tournament week.

3yearsThese measurements don't take much time to collect and they can be useful in evaluating how the maintenance work should be adjusted to achieve the desired green conditions.


What about the work that was done to get this clipping volume, and the conditions produced?

  • On the greens at Keya GC, 8.5 g N and 3.5 g K/m2 since the start of 2015.
  • Mowing height for the tournament was 2.6 mm with the Shibaura 22 inch GEXE.
  • Except when adjusted due to weather, the greens were mown 2x each morning, then rolled with a Toro lightweight roller, and then were mown 1x at the end of the day.
  • Primo Maxx and soil surfactants applied to the greens.
  • Irrigation added as necessary to prevent dry spots.
  • Morning green speed during the tournament rounds ranged from 10.7 to 11.2 feet.

"No more than one third of the the total leaf surface ...

... should be removed at a given mowing," reads the Lawn Management Through the Seasons guide from the Penn State Center for Turfgrass Science. "Thus, if the turf is cut at two inches, it should be mowed when it reaches a height no greater than three inches."

Breaking the one-third rule on bermudagrass in Vietnam

Run a Google search on "one third rule mowing" and you will get pages and pages on this "rule." From Cornell University, this explanation:

After raising your cutting height, the next most important thing you can do is to observe the “One-Third Rule” when mowing: never remove more than one-third of the grass blade. That means if your mowing height is 3 inches, you need to mow when the grass is about 4.5 inches tall.

This is pretty standard advice, but where does it come from, and how strictly does one need to follow this rule? This is based, as far as I can tell, on a really interesting paper by Franklin Crider published in 1955: Root-growth Stoppage Resulting from Defoliation of Grass.

I read this in its entirety last weekend, and was struck by the way the percentage removal was done. It was not by length of leaf. The percentage of cutting was determined as a percent of the verdure volume, not leaf length or plant height. I really liked the paper, and was interested to learn about the root blacking technique and the absolute cessation of root growth that occurred with certain defoliation treatments.

Most interesting to me were the data and discussion on just how much the root system is decreased by mowing. There is also a nice photo and discussion of root system size when grass plants are mown at all, versus left "unmolested" for a growing season:

The roots of the clipped plants [clipped 3 times over 247 days for cool-season species; 2 to 4 times per 146 days for warm-season species] weighed only one-eighth as much as the roots of the unclipped ones. This striking difference in root production by clipped and unclipped plants was manifest as well in the development of the plants as a whole. Compared with [sic] unmolested plants, the mature, clipped specimens were greatly lacking in size and vigor."

I like the thought of trying not to cut grass too short, and trying not to remove too much of the leaf at one mowing. But if the grass must be cut a different way at times, then go for it. Doug Brede's Turfgrass Maintenance Reduction Handbook has a great section on the one third rule in which he explains just how absurd it is, calling "an absolute like the one third rule ... strangely out of place" in a discipline like turf management that usually "deals in shades of gray."

And Brede has a fine replacement for the one third rule too.

So what can we use in place of the one-third rule? What general guideline can be employed to govern mowing frequency?

How about the plugged-up mower rule: "If your mower plugs up when you're mowing, you let it grow too tall." This guideline makes more sense for the turf caretaker who's battling practical limitations of budget, equipment, labor, and weather. This guideline also allows added flexibility for managing low maintenance turf.

The Crider paper on root growth and defoliation is interesting but one can read it and realize a few things:

  1. It is about forage grass more than turf.
  2. It does not measure turf or surface performance, rather it looks at root growth.
  3. It was not based on mowing height and cutting a percentage of leaf length; it was based on grass allowed to grow for two months and then cut to different percentages of verdure volume.

For more about mowing, original research, dogma, and the one third rule, see:

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.

3 Reasons Sheep are Better Than Cows for Mowing Fairways

The 1st at Ootacamund Gymkhana Club (founded 1896) is strikingly reminiscent of the 10th at Augusta National. This long dogleg left plays steeply downhill in a wide corridor between tall evergreen trees. Unlike Augusta National, no mechanical mowers have ever been used on this fairway.

In the never-ending debate of which is best for fairway mowing — conventional 5-reel mowers, lightweight 5-reel mowers, triplex mowers, ground-driven gang mowers, PTO-driven gang mowers, sheep, cows, other ungulates, rabbits, rotary mowers, scythes, etc. — I look in this article specifically at the intriguing differences between sheep and cows. As you will see, sheep beat cows in three categories of critical importance to the greenkeeper: soil compaction, efficiency, and quality of cut.

Soil compaction: The average cow will weigh about 725 kg. A sheep is just 10% of that, and lambs of course are even less. When fairways are mown with cows, more cultivation activities must be undertaken to relieve soil compaction. Even after a heavy rain, sheep can be sent out to mow, but care must be taken with cow mowing after rain events and in poorly-drained areas. Note that in sandy soils, which are resistant to compaction, this advantage of sheep is negated, and cow mowing can be used with little fear of soil compaction.

Efficient sheep mowing

Efficiency: Fairways cover a large area, usually more than 10 ha for an 18 hole course, and efficiency is of utmost importance to prepare a course for play. Sheep can be herded into any arrangement to go down the fairway in unison. I like to send them in groups of 12, as shown above, with 9 in front to mow a 4 meter swath; the 3 sheep following immediately behind clip any blades not cut. Other turf managers may prefer a different arrangement, 7-2 being popular when fewer sheep are available, and 12-4-2 (sometimes called 3-row mowing) at higher budget properties. Regardless of the arrangement, sheep mow a fairway rapidly and completely.

Inefficient cow mowing

Cows, on the other hand, face in all directions and mow a patch here and a patch there. Fairways mown with cows take approximately 40% longer to cut completely, by my estimation, which often results in the cows interfering with approaching golfers, as mowing simply cannot be completed ahead of play.

Quality of cut: No matter how light the footprint, or how incredibly efficient a mower is, the end result must be a high quality of cut in order to produce the desired playing surface. This is where sheep really excel. Their self-adjusting mowing height produces the ideal height of cut (HOC) on any surface, and they cut precisely by biting off the leaves in a fluid scything motion (see video above). Cows aren’t able to mow at extremely low HOC, but do mow at a HOC acceptable to most golfers. However, the tearing action as cows mow (see video below) results in more damage to the grass, possibly increasing the grass water use and creating entry points for fungal pathogens.

Counting Down, Top 5 Posts of 2009

Banner_1I started this blog on 1 January 2009. After nearly five years of writing, I thought it would be interesting to look back at the most popular posts of each year. There is a lot of information in the back pages of the blog.

In 2009, almost no one read what I was writing. Now, there are more visitors to the blog on a slow day than there were on the busiest day in 2009.

So what were the most popular posts (as measured by pageviews) in 2009? Here they are.

  1. Mowing Patterns & Grass Color
  2. Core Aeration of Putting Greens ... how much is enough?
  3. Sodium Chloride for Weed Control
  4. Seeded Sea Spray Seashore Paspalum
  5. Turfgrass at Dubai

Coming up I'll share the most popular posts of the succeeding years. 

Presentation Video: Five Easy Ways to Improve Turfgrass Performance

Manilagrass_demoAt the Philippines Turfgrass Forum on 1 August, I spoke about Five Easy Ways to Improve Turfgrass Performance. The presentation slides are available for download as a 9.3 MB PDF file, and UPLB Research, Development, and Extension have recorded a video of the presentation and made it available to the public.

In the presentation, I talked about the management, selection, and optimization of mower adjustment, grass variety, soil moisture, soil organic matter, and nitrogen application rate as being the five things, all interrelated, that when moved closer to optimum management will be sure to produce improved turfgrass. Watch the video here (20 minutes).

If I Were a Superintendent . . .

I would give this topdressing technique a try. Todd Pippin has written an article for the Green Section Record describing his five-day program of adjusting mowing heights and other tricks that can be used to allow topdressing sand to work its way into the canopy without excessive mower pickup.


The necessity of regular sand topdressing to dilute organic matter on golf course putting greens is unquestioned. The problem faced by those managing the turf, however, is that with low cutting heights on greens, the sand that is applied as topdressing sometimes gets picked up by the mowers on days succeeding the topdressing event.

Pippin's program (you really should study the article with full details) involves a grooming and mowing at 10 to 15% below the starting mowing height on the day of topdressing (for example, mow at 2.8 mm when normal height is 3.2 mm. The topdressing is followed by a heavy irrigation. On the day after topdressing, the mowers are set at a height 10 to 15% above the starting mowing height (for example, mow at 3.7 mm instead of the normal height of 3.2 mm). On days three, four, and five, the mowing height is gradually lowered. Pippin reports that this program allows topdressing sand to be applied with minimal disturbance to ball roll speed and almost no pick up of sand by the mowers. 

If I were a superintendent I would give this program a try. Sand topdressing is essential in maintaining adequate aeration porosity in the soil. If you have a chance, give this program a try and see how it works at your course.