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. 

How Much Potassium Does Grass Require?

In last week's TurfChat, in which we discussed the relationship between soil nutrient levels and weeds, I mentioned that recommendations for soil potassium (K) tend to be unreasonably high. We can see that particular section of the discussion beginning at the 31:55 time of the TurfChat video:


The most accurate, and consequently, the most useful, guidelines for interpreting soil nutrient levels for turfgrass are the minimum level for sustainable nutrition (MLSN) guidelines. These guidelines have been specifically developed for turfgrass with special consideration of the sandy soils that are commonly used for high traffic turfgrass areas.

Pace_mlsnThe MLSN guideline for K is 35 ppm.

I mentioned in the video that conventional guidelines are much higher, ranging typically from the conventional PACE Turf guideline of 110 ppm to the Penn State University target of at least 180 ppm. But there is no reason for soil K to be so high, nor can we expect most turfgrass soils to hold that much K.

When we look at the results of relevant research papers, we see that the recommendations developed after the completion of carefully controlled experiments give guideline levels very close to the MLSN guideline. Here are just a selection of typical results.

Ebdon et al., 2013: less than 50 ppm, Morgan extraction, "there were no observed changes in shoot and root growth in response to K fertilization even at low soil test K levels"

Paul, 1981: 20 ppm, ammonium acetate extraction, "beyond 20 ppm, there is no response to K fertilization"

Sartain, 2002, 30 ppm, Mehlich 1 extraction, "the critical Mehlich-1 extractable level of soil K appeared to be near 30 ppm"

Woods et al., 2006, less than 50 ppm, Mehlich 3, Morgan, and ammonium acetate extractions, "the current target ranges of extractable K in sand rootzones promote K fertilizer application that may be detrimental to turfgrass performance. Recommended levels of soil K should be reevaluated to avoid gratuitous use of K fertilizers"

The MLSN guidelines have done just that, and the methodology used to develop the MLSN guidelines results in a recommendation in line with those developed through controlled field research.

There are a number of implications resulting from using outdated and inaccurate K guidelines. It is obviously a waste of money to apply unnecessary potassium. There is wasted thought in trying to solve an imaginary problem. Application of K will reduce, unnaturally, and possibly to the detriment of plant health, the amount of calcium and magnesium in the grass. In some situations, it is expected that addition of K will increase the number of weed species that can grow. And unnecessary applications of K may cause other unexpected problems, such as increased disease.

Nutrient Supply and Plant Species Diversity

On March 28 (or March 29 in Asia), Episode 23 of the Turf Diseases Turf Chat will be on the subject of Soil Nutrients and Weed Management. This promises to be an interesting discussion, led by Dr. Scott McElroy from Auburn University and hosted by Dr. Larry Stowell of PACE Turf.

It is a well-known phenomenon that application of nitrogen favors grasses and reduces species diversity (i.e. reduces the number of weedy species), while increasing the soil pH through addition of lime, and adding potassium fertilizers, as an example, can increase the prevalence of weeds. In a brief exchange on twitter last week, we discussed this, and decided to make this subject the focus of the upcoming Turf Chat.

Dr. McElroy says that this phenomenon is already known, while I would argue that despite it being noticed more than 150 years ago, and the mechanisms of this worked out more recently, among turfgrass managers, there is not universal knowledge of these principles.

Woods_rossi_park_grassThat was the subject of an article I wrote with Dr. Frank Rossi from Cornell University about the Park Grass Experiment and some of the results from this classic experiment, especially the noted absence of dandelions from plots to which potassium fertilizer is withheld.

For more detail about this, please read our article about Park Grass from the Green Section Record, and you can find a list of references at the end of that article for additional reading. Of particular interest may be this one, by Silvertown et al., The Park Grass Experiment 1856-2006: its contribution to ecology.

A Botanical Walk at Ishigaki Island

This short video will be of interest to golf course architects, superintendents, and anyone involved in the management or development of golf courses in tropical and sub-tropical Asia. Cut to just eight minutes in duration, it is a narrated walk along 5 km of Ishigaki island coastline, describing the grasses encountered and showing the ecological setting in which these grasses grow naturally.

Ishigaki has a climate very similar to that of Hainan Island in southern China. Seashore paspalum is overused there (and elsewhere in Asia), despite its high cost of maintenance and well-known propensity to be completely overtaken by bermudagrass and manilagrass. In this video, you can see for yourself why that is, and learn what grass is sure to perform much better in Southeast Asia. 

Webcast from the Australian Turfgrass Conference: Micah Woods on grass selection in Asia

The Australian Golf Course Superintendents' Association provide a great service by making so many of the presentations from their annual conference available for online viewing

At the 27th Australian Turfgrass Conference in Adelaide, I gave presentations about turfgrass nutrient requirements, about grass selection, and about managing turf in microclimates.

In this presentation about grass selection, I spoke primarily about manilagrass (Zoysia matrella), bermudagrass or green couch (Cynodon), and seashore paspalum (Paspalum vaginatum). You'll see in this video representative photos of the different grasses and will learn how manilagrass persists and provides a fine turf even with minimal maintenance. In Southeast Asia, seashore paspalum tends to be overtaken by bermudagrass, you will see, and bermudagrass tends to be overtaken by manilagrass. This short video makes a case for using more manilagrass and less bermudagrass and seashore paspalum.

Ten Years Ago on a Golf Course in Japan: part 3

If you've flown into Narita Airport in Chiba prefecture near Tokyo, and have happened to look out the window, you may have been surprised when you flew over golf course after golf course as the plane descended. Chiba prefecture has more than 150 golf courses, placing it third among Japanese prefectures in golf course count. Only massive Hokkaido in the north, and Hyogo prefecture near Osaka, have more courses.

This map shows a portion of Chiba prefecture where there is an especially high concentration of golf courses. The satellite image was taken in the winter, so we see that the korai (Zoysia matrella) fairways and noshiba (Zoysia japonica) roughs are dormant.

View Larger Map

Many of the golf courses at Chiba were constructed in the golf course building boom of the early 1990's, and for these courses, there is a pesticide ban. I was a superintendent in 2000 and 2001 at Habu CC, which opened in 1996 and was thus subject to the pesticide ban. Here the inspection team from the prefectural government made a visit to inspect the course, the maintenance building, and our records. We could use wetting agents, Polyoxin-D, and phosphites; other than that there was very little in the way of chemical control products that we could use. 

Chiba-ken chemical inspection team

One thing that I focused on, with the limited resources we had to maintain the course, was to have the central playing corridors in as good a condition as possible. We tried to have perfect greens, tees and fairways as good as they could be, and less attention was paid to the roughs, particularly in out-of-play areas. You can see here, in a view from behind the 14th hole at Habu CC, that there are some weeds growing behind the green on this par 5.

mow 14 approach Habu CC

I've sometimes had long discussions with Japanese greenkeepers about the philosphy of balance in golf course maintenance. If resources for maintenance are limiting, I've always strived to make green perfect and the playing corridors as good as possible. In Japan, there has historically been the idea that there should be balance on a course, and that all of the areas should be maintained. 

Balance is alright if you have enough resources to maintain every square meter at a high level, but if those resources are not there, then striving for balance is a sure way to have mediocre conditions all over the course. I think every course has the resources to make their greens perfect, and I am fine to let some out-of-play areas be a little less-maintained if I can ensure the greens will be excellent. This is still a challenge in Japan, because many courses were built in mountainous areas in a bubble economy and are inherently expensive to maintain. Maintenance budgets then get cut again and again, and it is very difficult to maintain these courses with the desired balance. I was lucky in my work, to be a foreigner, and to have an American boss. In this situation it was easier, culturally, to focus our maintenance efforts on the playing corridors.

Fertilizer and Weeds at Park Grass

An article I wrote with Dr. Frank Rossi about the Park Grass experiment at Rothamsted has recently been published in the USGA Green Section Record. (Download the article here). This experiment has been ongoing for more than 150 years and it involves fertilizer treatments applied to grassland and the many measurements that have been made over the years on the experimental plots. One of these measurements is the botanical composition of the plots, and the results are amazing.


When nitrogen in the form of ammonium sulfate is applied as the only fertilizer, finer grasses predominate and weeds are not present. When potassium is applied, dandelions and other weeds proliferate. Lime also causes an increase in weedy species. 

The recommendations for complete fertilizers along with lime treatments that are commonly made for for cool-season lawns and other general turf areas are probably contributing to an increase in weed abundance as well. Is it possible that less fertilizer could also lead to less weeds and less herbicide use? That is certainly something to consider, and Dr. Rossi and I suggest that the results of the Park Grass experiment are worthy of further attention from turfgrass managers.

Sandcapping or topdressing: which is better?

Woods_fwy_sandcap I have often advocated sand topdressing rather than sandcapping for golf course fairways and roughs. Why? Because sandcapping at the time of construction makes for a much higher construction cost, higher maintenance cost, and invariably leads to deteriorating playability over time. Conversely, a sand topdressing program provides better playing conditions, easier maintenance, and all for a much lower cost. I am not referring to drainage. Drainage is required for both a sandcapped system and a topdressed system. But sandcapping is not drainage.

Sandcapping a turfgrass area with 10 to 15 cm of sand has a high upfront cost and then forces higher maintenance costs as well, for that sandy rootzone will require more fertilizer, more irrigation water, and more surface organic matter management than would an area not sandcapped. And what happens if the organic matter is not controlled? See below. What used to be a fine zoysiagrass is now a mixture of cowgrass and sedges. A layer of organic matter built up at the surface creates a perfect growing environment for weeds that thrive in wet soils. And all that sand underneath? One might as well bury money in the ground. Once the organic layer builds up over the sand, there is no benefit whatsoever to having the sandcap.

Dr. Alec Kowalewski has recently published some intriguing articles that show just how effective sand topdressing can be as an alternative to sandcapping. Not only does he demonstrate the substantial cost benefits of a topdressing (or built-up over time sandcap) program compared to a sandcap installed at the time of construction, his research also shows how turf quality improves and drain line spacing can be extended when a topdressing program is implemented. 

"Preliminary findings from this research," he wrote, "suggest that as little as 1/2” (1.25 cm) of sand can be used to improve athletic field playability by substantially decreasing the surface moisture content." His results show that once 2.5 cm of topdressing sand has been applied, drain line spacing at 3.9 meters provided sufficient drainage and surface stability. After a 5 cm topdressing layer was established, and assuming surface slope is at 1% or greater, then drain line spacing could be extended to more than 6 meters while still producing the desired surface conditions.

For full details, see:

Kowalewski, A. R.; Crum, J. R.; Rogers, J. N. III. 2010. The built-up sand-capped athletic field system. MSU Turfgrass Science Program. April 7. p. 1-7.

Kowalewski, A. R., J. N. III Rogers, J. R. Crum, and J. C. Dunne. 2010. Sand topdressing applications improve shear strength and turfgrass density on trafficked athletic fields. HortTechnology. 20(5):p. 867-872.

Kowalewski, A. R., J.R. Crum, J. N. III Rogers, and J. C. Dunne. 2011. Improving native soil athletic fields with intercept drain tile installation and subsequent sand topdressing applications. Soil Sci. 176(3): p. 143-149.

Ballmark With sandcapping at the time of construction there is a high upfront cost, turfgrass and playing conditions that deteriorate, and there will be the need for a disruptive and costly renovation to remove the organic layer that will invariably develop at the surface. Planting grass onto native soils and then topdressing with sand results in lower construction costs, lower maintenance costs, and better playing conditions over time with longer intervals between disruptive renovation projects. It is the surface conditions that matter for the playing of sports on grass, and topdressing with sand is a proven method to create the desired surface conditions.

Turfgrass Research at the University of Tennessee

Tennessee Turf Research

I visited the East Tennessee Ag Research and Education Center in Knoxville yesterday to see many of the turfgrass experiments now underway. This large facility has vast swaths of turfgrass plots sweeping down to the Tennessee River.


What really caught my eye, and is now under construction and nearly ready for planting, is an exciting new research center. The Center for Safer Athletic Fields is a partnership between Astroturf® and the University of Tennessee. Dr. Jim Brosnan explained how these 60 miniature athletic fields and other research plots at the Center have been designed for many interesting experiments. From the press release announcing this Center:

The unique outdoor research facility will comprise 60 small-scale athletic research fields constructed from a variety of playing surfaces. UT turfgrass scientists will compare the safety and performance of synthetic playing surfaces to natural grass surfaces. Field qualities will range from those employed for professional-level sports to surfaces used by schools, public parks and recreation fields. 

Some of the other research trials I saw included:

  • Bluegrass evaluation plots
  • Zoysiagrass variety evalution
  • A multitude of weed control plots, including some really interesting pre-emergent product results, Poa annua control trials, and innovative combinations of herbicides with cultural practices to optimize weed control
  • Seedhead and disease control trials
  • Ultradwarf bermudagrass and seashore paspalum and zoysiagrass on putting greens

Ut_overseed The UT Turfgrass Field Day will be held on September 15, 2011. I wish I could be there for that. Seeing the various grasses right at the end of summer, when we might expect warm-season grasses to be at their best, and cool-season grasses to be at their worst, would be an ideal time to see which grasses perform best and which maintenance practices and products perform well to create the desired playing surfaces.

Herbicide Safety on Newly Sprigged Bermuda and Paspalum

Patton_sulfonylurea_weed_tech2010-1This article by Patton et al. about the safety of various herbicides on seashore paspalum and hybrid bermudagrass during establishment/grow-in will be of interest to many turfgrass managers in Asia. Entitled Sulfonylurea Herbicide Safety on Newly Sprigged Bermudagrass and Seashore Paspalum, the research project was conducted in Arkansas and Louisiana and found that foramsulfuron, halosulfuron, metsulfuron, sulfsulfuron, and trifloxysulfuron can be used to control weeds in establishing Tifway bermudagrass.

For seashore paspalum, metsulfuron and halosulfuron applied two or four weeks after sprigging and sulfosulfuron applied four weeks after sprigging provided weed control without causing too much injury to the seashore paspalum turf. The Aloha variety of seashore paspalum was used in this experiment. If you are interested in using sulfonylurea herbicides on seashore paspalum, you will want to read the article for yourself.