Previous month:
November 2014
Next month:
January 2015

December 2014

Top 10 posts on the blog in 2014

These 10 posts in 2014 had the highest number of pageviews.

  1. Seasonal nitrogen use, how much and when?
  2. It's here! Chemical Control of Turfgrass Diseases 2014 (note, the 2015 guide is here)
  3. It cures fairy ring and prevents fungal pathogens: an anecdote about ammonium sulfate
  4. "The salesmen all suggest calcium"
  5. A Waste of Time and Money
  6. Cool-season grass in a tropical climate
  7. A paper packed with data about N, P, and K
  8. Another five articles every greenkeeper should read
  9. 5 links: irrigation, soil moisture, syringing, and controversy
  10. Relationship between soil moisture and surface hardness

For top posts from previous years, the lists are here.

A look at 2014 pageviews on this blog, and my 10 favorite posts that didn't make the top 10

Tomorrow I'll list the 10 posts from 1 January 2014 until today that received the highest number of pageviews. Today I want to have a look at all the posts, and the view counts, and share my pick of 10 posts that I really enjoyed writing, or that have generally important information, but that did not make the top 10 in pageviews.

This will be the 158th post of 2014. In the 157 posts before this one, the minimum pageviews were 33, and the maximum were 619 (data from Google Analytics). The median pageviews for a post are 112. Here's a histogram showing the pageviews for each post.


Only those posts with 340 pageviews or higher made the top 10 this year. A full 25% of the posts had 72 or fewer views, 50% of the posts had from 73 to 186 views, and the top 25% of the posts had more than 186 views.

ViolinThe violin plot at right shows all the posts to date in 2014, with the pageviews. Tomorrow those 10 at the top with more than 340 pageviews will be listed.

But there are 147 other posts from this year with a lot fewer pageviews. Here are 10 of those that I really like, and that you might like to read sometime.

  1. Calculating potassium fertilizer requirement using the MLSN guideline which introduces this ShinyApp that one can use to input grass species, N rate, and soil K level, to determine how much K, if any, is required as fertilizer.
  2. Technical details of the Global Soil Survey Report, including the entire year 1 dataset. First, this is a really exciting project. Second, we are sharing all the code and data for this project, so anyone who wants to check the validity of our results, or compare the data we are using to their data, can do so at any time. And we share a lot more data than we have analyzed, so others who are interested in these same topics can also study these data.
  3. Hitting all of our goals. This is a superb video interview with Don Mahaffey that everyone should watch. It's only 13 minutes. And it's really good.
  4. In which I wrote a long answer to a short question about golf course grass in Rio de Janeiro. This one won't be of interest to everyone, but if you are involved with grass in the tropics, this analysis of the relative merits of different species is something you'll probably want to be aware of.
  5. Tropical carpetgrass part 2: ugly duckling or swan? In the tropics, this grass works great, and yet it gets disparaged as an ugly duckling by many. This is a grass that should be used more often in the tropics.
  6. Can putting green N applications be scheduled using Kreuser's GDD model for trinexapac-ethyl? I sure hope not, but it seems there is some linkage of GDD and N applications in practice. Because GDD always go up with higher temperatures, but the N demand of cool-season grasses should not increase at very high temperatures, I suggest in this analysis that GDD models for trinexapac-ethyl application should NOT be linked to N application.
  7. A Fortunate Stroke of Serendipity. Stumbling across Koch's posulates in unexpected places is serendipity indeed.
  8. New motion chart to look at relative growth potential of cool and warm season grass. I look in this chart at the cumulative difference between GP of cool season and warm season grass. From this, and especially when the slop of the line changes, one can get an idea of optimum dates for overseeding at a location.
  9. Misunderstanding the MLSN Guidelines. My response to a discussion of the guidelines in a Turfnet webinar, with pertinent comments from Jon Scott.
  10. A note on light and grass selection in warm-season areas. I wrote this to answer some questions I'd received about when manilagrass would be expected to outperform Cynodon.

"This publication is intended for professional turfgrass managers who use fungicides as part of an overall disease-control program"

Selection_009"This publication" is Chemical Control of Turfgrass Diseases 2015 by Paul Vincelli and Gregg Munshaw. A wealth of information about diseases is packed into only 24 pages.

And it is not just about chemical control. Common turfgrass diseases are described, the environment and season in which the disease is most likely to occur are explained, and the best control measures for each disease are given. There are also informative sections about fungicide resistance, improving spray efficacy, detrimental effects of pesticides, and much more. This is a guide that will be of use to every professional turfgrass manager.

Turfgrass ecology, part 4: "the luxuriance of our meadows and pastures"

After writing about what happened to abandoned turf in Japan, Thailand, and Michigan, I remembered the Broadbalk Wilderness experiment at Rothamsted. I was going to share only that, but as I was reading the introduction to Hubbard's Grasses today, I was struck by the relevance of this passage:

Most visitors to the British Isles are deeply impressed by the luxuriance of our meadows and pastures, as well as by the fine crops of the cereal grasses – wheat, barley, oats, and rye of arable land. The rich growth of the herbage grasses gives one the impression that here is a land ideally suited for such plants. This inference is correct, for our climate is most favourable for the production of this luscious green growth during a large part of the year. It is not realized, however, that these associations of grasses are almost entirely artificial in origin and due to the continuous labours of many generations of our ancestors, together with the cumulative action of the grazing and treading of their domestic animals. Under our climatic conditions and on most soils, these artificial grasslands, when removed from the control of man and beast and left to the effects of competition and natural selection, gradually revert to scrub, and in most cases from scrub to forest.

And that is just what happened, and quickly, at Broadbalk Wilderness. In 1882, about 0.2 ha of the Broadbalk wheat field was abandoned. It was fenced off to prevent grazing, and the wheat was not harvested, so the seeds could fall on the ground and have the opportuninity to regenerate. What happened? From Rothamsted's Guide to the Classical and other Long-term Experiments: "The wheat did not compete well with the weeds, and after only four years the few self-sown wheat plants that could be found were stunted and barely recognisable as cultivated wheat. One half of the area has remained untouched; it is now woodland dominated by ash, sycamore and hawthorn; the ground is covered with ivy in the densest shade, and with dog's mercury and other species present where shade is less dense."

Selection_006The other half has been stubbed (woody species removed annually), and since 1957, half of the stubbed section has been treated by mowing, then grazing, and since 2001 by mowing. 

So part of this abandoned field is woodland, and part is stubbed, and what happened in the area where mowing began in 1957? "The grasses did not increase substantially until the site was grazed by sheep. By 1962, perennial ryegrass and white clover had appeared, and they are now widely distributed. The ground ivy has almost gone, and the growth of other species is much restricted."

The Guide to the Classical and other Long-term Experiments is great reading. One finds an introduction and summary of Broadbalk Wilderness, and Park Grass, and Garden Clover, and Exhaustion Land, and so many other agricultural, botanical, and ecological experiments.

More about grasses on golf courses in Thailand: a Christmas Eve miscellany

Sunset_banyanGolf in Thailand at this time of year is really pleasant. I often use the words clement and salubrious, with additional modifiers, to express just how pleasant I find it.

Over the past 20 days in Bangkok, there has been no rain, and the temperature has ranged from 19 to 34°C.

I've written about the grasses one finds here, and I have also put together this photo gallery of the typical grasses. Most putting greens are hybrid bermudagrass, and after that comes manilagrass, and there are comparatively few courses with seashore paspalum greens.

Through the green, the percentage of courses with bermudagrass goes down, and the percentage with manilagrass and seashore paspalum comes up.

Turfgrass @ Thailand

At the Sustainable Turfgrass Management in Asia 2015 conference, we will be talking about these grasses, and we will have a pre-conference seminar in which we discuss the design and construction of golf courses in Southeast Asia.


It hasn't rained in Bangkok for 20 days, yet on the seashore paspalum fairways I played today, this was the result from multiple shots that landed in the fairway: debris (organic matter, or mud?) on the ball.

2014-12-24 13.50.15 2014-12-24 11.20.57 2014-12-24 11.38.52
I think the cause of this is related to the grass species. In Southeast Asia, when one does not keep the soil wet, seashore paspalum will eventually be overtaken by better-adapted species that thrive in drier soils. So seashore paspalum fairways must be kept really wet if the grass is to persist. One can topdress with large amounts of sand to minimize that problem, but that is really expensive.

A recent post on about seashore paspalum had some interesting comments from golf course superintendents and golfers and architects about this species. The consensus -- it requires a lot of inputs and can be very expensive to maintain.

I've got lots of ideas about grass selection and construction methods (especially sandcapping of fairways) and will be working on developing those for discussion at the upcoming conference. 

An elemental cartogram: the relative mineral nutrient amounts in turfgrass leaves

The periodic table of the elements usually looks like this.

image from"Standard form of the periodic table" by DePiep is licensed under CC BY-SA 3.0

Elemental cartograms show the periodic table in a different way, with the area of each element modified by a theme. The most abundant elements in turfgrass leaves are carbon (C), oxygen (O), and hydrogen (H). The grass obtains these elements from water (H2O) and from carbon dioxide (CO2). Grass is never deficient in C, O, or H; these 3 elements make up 90 to 95% of turfgrass leaves, by mass.

The elements that the grass obtains from the soil, and that are sometimes applied as fertilizer, are termed mineral nutrients. I made an elemental cartogram (using this tool from Babak Sanii) for mineral nutrients in creeping bentgrass leaves, omitting C, O, and H because they would otherwise overshadow all the others.

Turf_leaf_elemental_cartogramThe macronutrients nitrogen (N) and potassium (K) are relatively large, and then comes phosphorus (P) and the secondary nutrients calcium (Ca), magnesium (Mg), and sulfur (S). The other elements are used by the grass in such small amounts that they don't stand out in this type of chart.

As an example, iron (Fe) is usually the micronutrient at the highest concentration in leaves, often at about 100 ppm (100 mg kg-1). Nitrogen will be at about 4%, which is 40,000 ppm. So there is 400 times as much N in the leaf as there is of the most abundant micronutrient, Fe.

For more about the different elements, what they do in the turfgrass leaves, and in what amounts they are normally found, see:

A course like no other

The distinctive crest of the Club

I love hill stations. And the best hill stations all have golf courses. One of my favorites is Kodaikanal Golf Club (founded 1895). At an elevation of 2,100 m in the Palni Hills, and just 10° north of the equator, the clubhouse sits at the edge of a cliff, high above the plains.

Kodaikanal is 2,100 m above sea level and receives the most rainfall in southern Tamil Nadu

One of the great attractions of Kodaikanal (Kodai) is the temperate weather. This was my third visit. Each time I've taken the winding road up the mountain, I've watched the roadside grasses change with each kilometer. One sees the tropical grasses of the plains on the lower reaches of the mountains, with kikuyugrass (Pennistetum clandestinum) starting to appear as one gets closer to Kodai.

The uphill approach to the wide-open first

Ecologically, the golf club sits on a sky island. That is, it is at such an elevation, and surrounded on all sides by lowlands of a completely different environment, so one finds many endemic species here – along with introduced plants such as kikuyugrass.

Memani2Club Secretary G.S. Mani (pictured with me at right) takes special care to employ organic practices on this property.

I've been impressed with the fine conditions produced at this hill station course with a minimum of inputs, no pesticides,and only the smallest amounts of organic fertilizer. There is a real focus on improving the environment by providing wildlife habitat, removing invasive Acacia tress, planting of native species, and developing natural wetlands.

You may have noticed the fence and gate to enter to course, and on the approach to the first, there was a net around the green.

At the fourth, one can see the net that encircles the green – and the fine turf around the green.


Nets are placed around the greens every night to keep Indian gaur from walking and grazing on the green surfaces

Every night, Indian gaur come out of the forest and onto the course, starting from the 16th hole. This is the world's largest species of wild cattle, larger than the American bison, and the nets around the greens help to keep the gaur off the carefully maintained putting surfaces.

There are a lot more wildlife here than Indian gaur. Especially around the clubhouse, practice green, first tee, and 9th and 18th greens, one finds troops of bonnet macaques. This one is running across the kikuyugrass on the first tee.

In the fairways one finds kikuyugrass and common carpetgrass (Axonopus affinis) and many other species that are managed to produce a good playing surface.

On the greens, which are rolled multiple times each week to improve the smoothness, the primary species is blue couch (Digitaria didactyla), with some patches of invading kikuyugrass.

Clouds blowing in just before sunset at Kodaikanal Golf Club

Another great hill station is Ootacamund (Ooty), about 6 or 7 hours drive, on a separate Sky Island. One finds imported gorse on the golf course at Ooty, but I don't think there is any gorse at Kodai.

If you like reading about hill station golf courses, you may be intrigued with the fairway maintenance at the Ootacamund Gymkhana Club. That Club was founded in 1896, but no mechanical mowers have been used on the fairways. Photos and videos here of the fairway mowing at Ooty.

Kodai has more conventional fairway mowing, with a farm tractor pulling a well-maintained 3-gang reel mower. But with native grasses, cold mountain temperatures, no fairway irrigation, and no chemical fertilizers, there isn't a lot of mowing to do.

For photos and information about this fascinating place, this video from the 2012 IGU greenkeeping programme shows more.

What do wetting agents really do?

There is a good article by Karcher and Richardson in GCM about the effect of wetting agents. In the article, they point out something important:

It is often stated that some wetting agents move water rapidly through the root zone while other products retain considerable moisture near the surface, but the data to substantiate such claims is limited.

I have been surprised, in conversations with turfgrass managers, to learn just how prevalent that thinking is, that soil surfactants can be divided into classes that retain more water in the soil, or that act as penetrants and may reduce soil water content.

If some wetting agents really do retain more water in the soil, and other types make water move through the soil more quickly, there should be some data to show that, right? This should be such easy data to get if there really were an effect. Because there doesn't seem to be such data, it would seem that wetting agents don't really produce those diverging results.


What wetting agents do, when the soil moisture content is measured after application, is this. They increase the uniformity of soil moisture. From Karcher and Richardson:

Wetting agent products tested in this trial effectively reduced localized dry spot incidence and increased soil moisture uniformity over a wide range of depths (3 to 8 inches) compared to untreated turf.

This is same result reported by Soldat et al. in this 2010 Soil Science paper:

The uniformity of soil volumetric water content of the surfactant treatments was significantly greater, and soil water repellency was lower [and] … surfactant treatments were faster to recover from the drought … The surfactants had a minimal effect on soil water content … however the three surfactants significantly improved soil moisture uniformity compared with the untreated control in both years during drought conditions … These results indicate that the surfactants evaluated are effective tools for improving soil water content uniformity, maintaining good visual appearance, and reducing soil water repellency in sand-based golf putting greens under conditions of drought and irrigation restrictions.

The data show two things. Soil surfactant (wetting agent) applications increase the uniformity of soil moisture. Soil surfactant applications reduce localized dry spot. If there are data showing some wetting agents retain more moisture in the soil, and others make water move through the soil more rapidly, I would love to see them.

"Could you tell me?"

Ha Darklight wrote from Hanoi with this question:

Could you tell me, in late autumm, how to apply fertilizer for seashore paspalum grass to prepare for early winter?

In general, for northern Vietnam, I would expect seashore paspalum to use N and K in approximately the amounts shown in this chart.


The expected amounts in the chart are based on the growth potential (GP) for warm-season grass in Hanoi temperatures, with a maximum N for seashore paspalum set at 3 g N/m2/month when the GP is 1, and recognizing that seashore paspalum uses nitrogen and potassium in a 1:1 ratio.

Our conversation continued:

If I take up high levels of K, ex rates of 3

Whether he means 3 g K/m2/month or 3 times more K than N, I don't see how that would be helpful. My exact reply was "Seashore paspalum uses the same amount of K as it does N. You can add more K if you want to, but it won't provide a benefit to the grass."

Then came another good question from Ha:

How does K affects to diseases?

My answer: "Not much effect. If you are severely deficient in K, or apply way too much K, you may increase disease susceptibility. Application of N and K in a 1:1 ratio to paspalum ensures the grass has enough. Also, you should do a soil test to be sure."

Why should one do a soil test? Because if the soil contains a high amount of K, the grass can use that K, using the soil like a nutrient bank, and the amount of K applied as fertilizer can be reduced. Without a soil test, one doesn't know if all the K the grass will use must be applied as fertilizer, or if some portion of the K used by grass will be supplied by the soil.

"I started using the MLSN guidelines and was amazed with the huge impact this made"

I really like the technical aspects of turf nutrition, specifically identifying just how much of each nutrient is required to produce the desired surface conditions. This necessarily involves numbers such as the amount of the nutrient in the soil, the amount applied as fertilizer, how much labor was involved with the application, and the cost of those nutrients.

If you are also interested in these things, then I am sure you will find Jason Haines' post on this topic of great interest. He summarized this in his post Fertilizer Use 2014, but he didn't just limit the report to this year – he showed the data of fertilizer use and cost for the past six years.

image from


More detailed charts and data tables in his report on the excellent Turf Hacker blog.

For more reading on this topic, see: