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July 2009

Mowing Patterns & Sharp Mower Blades


Turfgrass appearance is enhanced by the mowing pattern. Careful attention should be given to the mowing pattern that will be used at any turfgrass area, because just as a good mowing pattern improves the appearance of the turf area, a poorly-chosen mowing pattern can detract from the appearance of the grass and may also waste time and money. Some mowing patterns are more efficient and can save time to mow a given area. But it is not just the mowing pattern that should be considered; having sharp mower blades is also critical in creating mowing patterns that last (and not inconsequentially, sharp mower blades are essential in maintaining healthy turfgrass plants).

In a recent study at the Sports Turf Research Institute (STRI), the striping effect produced when cutting the grass was found to be more pronounced when using a sharpened mower using no contact between the reel blade and the bedknife. The study was commissioned by Bernhard & Company, who manufacture sharpening equipment for mowers. Mowing is perhaps the most important maintenance activity for any turfgrass area, and mowing is essentially what separates turfgrass from forage grass.


The photo above (click the photo or here for a larger image) shows the damage that can occur when turfgrass is mowed with a maladjusted mower. This otherwise healthy sward of Zoysia matrella now has a white appearance because the leaf blades are all shredded. In addition to changing the color of the grass, making it less green, damaging the grass with a mower also puts a tremendous amount of stress onto the turfgrass plant, and may cause increased disease incidence and lack of vigor and a general decline in turfgrass performance. So, if we are to have beautiful stripes on the grass, or are to create any type of mowing pattern, whether it be complex or simple, the starting point is to cut with sharp mower blades.

How Much Phosphorus Does Grass Require?

Phosphorus is an essential element for healthy turfgrass plants, but phosphorus can also contribute to algal growth in natural water bodies, so turfgrass managers should try to apply only the amount of phosphorus that is required by the grass.

How much phosphorus is enough? An article by Doug Soldat and Bill Kreuser includes this very interesting photo showing a phosphorus deficient turf, but green and healthy bentgrass growing where a leaky spray boom had spilled a phosphorus fertilizer onto the turf.

Phosphorus deficient bentgrass at Wisconsin 

Phosphorus deficiency symptoms, which appear as purple turfgrass and apparently drought-stricken plants, can occur at Wisconsin when the soil phosphorus is less than 10 ppm on a Mehlich 3 soil test. The MLSN guideline for phosphorus is 21 ppm, a relatively generous amount when compared to the levels at which one sees deficiency symptoms, but still lower than conventional guidelines. Soldat and Kreuser have concluded that "Mehlich 3 soil test phosphorus requirement for sand based creeping bentgrass putting greens is likely not greater than 15 ppm."

Dr. Soldat has compared phosphorus to a light switch, noting that when there is enough phosphorus, the grass grows very well (light switch on), and when there is not enough phosphorus in the soil (light switch off), the grass does not grow well at all. But adding more phosphorus beyond what the grass needs, which is probably somewhere below 15 ppm, or the generous 21 ppm as per the MLSN guideline, will have no effect on the grass, will certainly cost money but provide no benefit in turfgrass quality, and will have the potential to cause pollution of water bodies through leaching or runoff. So we should try to minimize the amount of phosphorus fertilizer applied.

I have done soil nutrient analyses for golf courses throughout Asia, and one thing that is surprising is how high the phosphorus levels tend to be on golf course putting greens in Japan. Creeping bentgrass can grow perfectly well at a soil phosphorus level of 21 ppm (on the Mehlich 3 test), and in one year we can expect to remove about 0.5 g P m-2 though the collection of grass clippings, and we would expect removal of that much phosphorus to cause a decline in soil phosphorus of about 3 ppm. But it is common on golf courses in Japan to have putting green soil phosphorus levels at 200 or 300 ppm, ten or sometimes twenty times more phosphorus than is needed by the grass. 

What do I recommend?

  • Test your soil every year to ensure you will have healthy turfgrass, will not waste money on unnecessary fertilizer applications, and will minimize the chance of any pollution
  • If you have soil phosphorus levels at more than 21 ppm on the Mehlich 3 test, you will not see a turfgrass response from applying more phosphorus, so save your money and don't apply phosphorus in those situations
  • Be very careful about the amount of nitrogen fertilizer that you apply, recognizing that nitrogen is the element that will control the growth of the grass and the uptake of other mineral nutrients

Note on 26 July 2017: I've updated this post twice since I first wrote it eight years ago. I think in the first version I suggested keeping P at 35 ppm and not applying when soil P was above 35. That of course was before the MLSN guidelines were introduced in 2012, and that first version of the guidelines had a minimum for P of 18 ppm. I've updated this post again to adjust to the current version of the MLSN guidelines, which has a P minimum of 21.

For more about P, and another photo and soil test data showing just how low the P was to show deficiency symptoms, see this annotated photo from Ben Pease.

More Grass Photos From ATC


I have posted a selection of photos of different grasses on the Asian Turfgrass Center photo galleries at flickr. The photo galleries at are one of the most viewed portions of the site, and the photos at flickr are easier to find by searching, viewers can leave comments on the photos, and there are more options for viewing and using the photos. I hope you find them interesting, please sign up here to receive updates when new photos are posted, and please let me know if there are any grass-related photos you would like to see.

Core Aeration of Putting Greens . . . how much is enough?

Aerification of golf course putting greens is the most disruptive maintenance activity, but it is also one of the most important. Proper aerification creates a healthy growing environment for turfgrass. That healthy growing environment is very important when we consider the stresses that a putting green is subjected to: traffic, low mowing heights, nematodes, diseases, low light conditions -- the list is extensive. But putting greens are also the most important area of any golf course. Turfgrass managers should do everything they can to create a healthy growing environment for putting green turf. 


I have written about the importance of filling core aeration holes with sand, and this video from Washington State University shows how water does NOT easily enter aeration holes that have collapsed at the surface. Coring holes must be filled with sand to get the desired effect.

Problem_green Everyone knows that coring is disruptive, but having bad greens is even more disruptive! Having an effective core aeration program is a key to having good greens, and at many of the courses that I see in Asia that have recurring problems with the grass on their greens, we can trace the problems back to a general lack of core aerification, and a subsequent accumulation of organic matter at the putting green surface.

So how much coring is enough? It depends on the course, but I say that at a bare minimum, there must be at least 10% of the putting green surface area removed each year and replaced with clean sand in the holes. Ideally there would be 20% of the green area removed, and if the ownership of a course wants to have good greens, they will find a way to get this done. Chris Hartwiger and Pat O'Brien, agronomists with the United States Golf Association Green Section, recommend 15 to 20% of the green surface area be removed each year. Courses in Asia that remove less than 10% of the green surface area by coring each year tend to have recurring problems with their greens. The exact amount of surface area to remove must be decided on a course-by-course basis, but you can be pretty sure that you need to remove between 10 to 20% of the green surface area annually.

I would never make an aerification without first determining how much of the green surface area will be affected. The calculations are simple. We know the tine diameter and radius and can calculate the area affected by one core using the formula πr2. The number of coring holes per unit area can be calculated based on the tine spacing used on the machine; tines on 5 cm x 5 cm spacing will give 400 holes per m2. So as an example, 10 mm diameter tines used to aerify a green on 5 cm x 5 cm spacing will remove 3.1% of the green surface area. Using 12 mm diameter tines on the same spacing will remove 4.5% of the green surface area. 


All other factors being equal, the key determinant of recovery time from aerification will be the tine diameter. Larger diameter holes take a longer time to recover. So for efficient aerification, with the least disruption to the golfer, removing as much of the green surface area as possible while still having the fastest possible recovery time, my goal is always to use the closest possible tine spacing and an approriate tine diameter. If you are able to set your aerifiying machine to a 2.5 cm x 2.5 cm spacing, there will be 1600 holes per m2! But keep in mind that it is not the number of holes on the green that cause a disruption to putting quality. It is the time the holes remain open without the grass growing back over them that actually causes a disruption to play.

Here are some tips for effective core aerification of putting greens:

  • Ideally you will remove cores from 20% of the green surface area each year.
  • Be sure to remove at least 10% of the green surface area by coring.
  • Do whatever it takes to fill the holes with sand -- coring holes that are not filled with sand only have a temporary benefit to the putting green quality.
  • Because small holes are very difficult to fill with sand (because of bridging of sand particles at the top of the hole), I recommend the use of tines at least 10 mm in diameter -- 12 mm or 14 mm are even better.
  • I always try to minimize the tine spacing, making the holes as close together as possible. This is the most efficient way to core aerify while minimizing disturbance to golfers.

Fill Aerification Holes With Sand


This video clip shows the way water moves into an aerification hole filled with sand all the way to the surface. Notice how the water does not penetrate into the aerification hole that was not backfilled all the way to the soil surface. The full DVD of Water Movement in Soils is replete with interesting demonstrations of how water moves in soils and is available for purchase from the Department of Crop and Soil Sciences at Washington State University.

It is important to understand how water moves into new and old aerification holes. When core aerification is done, the holes must be filled with sand. If holes are not filled with sand, the result, over time, may be counterproductive, as it may lead to more hydrophobic conditions in the soil. When holes are filled to the surface with sand, and then regular sand topdressing is applied (I suggest about 0.012 m3/m2, or 1.2 cm annually) to keep adequate air space at the soil surface, and when solid-tine aerification is used as well, then there will be adequate channels for water to move into the soil, there will be adequate air space in the soil, and turfgrass conditions will be improved. 

Zoysia Greens & Fairy Rings


Last week I visited the Sritrang Golf Course in southern Thailand's Trang province. This is a low maintenance golf course on an army base, using native grasses, including a native Zoysia matrella on the putting greens.The green fee is quite affordable, from 300 to 500 baht for visitors, depending on the day of the week. That is about US$15 for an 18 hole round on a rugged course with boldly-contoured greens; a caddy will be about US$7.

I like zoysiagrasses in Southeast Asia because they tend to perform the best with the fewest inputs. Zoysia grows better year round, is healthy in both the dry seasons and in the rainy seasons, and the zoysia tends to choke out some of the weeds that invade other grasses. Zoysia is relatively immune from diseases, and it basically just grows. If I were spending my own money to build and grass a golf course in Southeast Asia, I would in almost all cases choose a type of zoysia.
The only disease I saw on the zoysia at Sritrang was fairy ring. This is a fungus that grows in the soil and creates hydrophobic conditions in the soil. You can see the dry spots in the turf near my feet in the photo at right, and you can see the mushroom growing in the turf. These are typical symptoms of the fairy ring fungus. The best control of fairy ring is accomplished by reducing the hydrophobicity, so the use of wetting agents to reduce dry spots combined with spiking or coring the greens to improve water infiltration can help. Applying some fast-release nitrogen from a source such as ammonium sulfate [21-0-0] at a rate of 1 g N m-2 can help to mask the symptoms of the fairy ring. And fungicides with the active ingredients azoxystrobin, flutolanil, triadimefon, polyoxin-D, or pyraclostrobin can control the basidiomycete fungi that cause the fairy ring symptoms.

But overall, zoysia is relatively foolproof in the climate of Southeast Asia, unlike seashore paspalum which is quite suceptible to diseases and dry spots and even death in extreme cases, or bermudagrass which struggles in the low light conditions of the rainy season and is prone to invasion by weeds. Zoysia is a grass you can plant to have a sustainable (low inputs, low cost, good quality) golf course in southern Thailand, and it should be used at more golf facilities throughout the region.

Thatch Control by Burning

Shiba_yaki This photo is of the shiba-yaki ceremony at Korakuen Garden (後楽園庭園) in Okayama, Japan. I visited this garden in 2008 and wrote about it on the ATC website. This is some of the most beautiful noshiba grass (Zoysia japonica) I have seen, maintained using traditional and simple methods. And one of those traditional maintenance practices is the burning of the dormant grass each winter. This burning improves the quality of the turf in the upcoming growing season. Burning the stems and other organic matter at the surface helps to reduce thatch buildup, creating a firmer surface. Weed seeds are destroyed by the heat of the fire. And burning the dormant turf also creates a natural fertilizer, with the mineral elements from the ash left to nourish the grass as it grows in the spring.


The photo above shows the layer of organic matter that builds up naturally near the surface of a turfgrass stand. This is a ten year old korai (Zoysia matrella) fairway in Western Japan. The organic matter buildup can cause problems with turfgrass quality because of too much water retention in the organic matter and a number of other problems associated with excessive organic matter. Removal of organic matter can be an expensive and time-consuming process; burning the turf when it is dormant is not expensive, but this traditional maintenance practice is not used frequently because of safety regulations. Also, most golf courses remain open during the winter,  and a recently burned turf does not make a good playing surface for the average golfer.


This is the fourth hole at The Cypress Golf Club at Hyogo-ken in early March. The noshiba rough has been recently burned, the creeping bentgrass putting surface is still green through the winter, and there is a dusting of snow on the mountains. Another advantage of burning the turfgrass is the dark color it gives to the ground. This will increase the soil temperatures during the spring and will cause more rapid growth of the grass when it does come out of dormancy.


Now we see the same hole at The Cypress Golf Club in May. The noshiba is growing well, the thatch has been reduced, and weeds are not a problem. The traditional burning of dormant zoysiagrass is not practical at every location, but the importance of organic matter management remains no matter where you are. If you cannot burn the grass, then consider other methods to manage organic matter accumulation: apply optimum amounts of fertilizer, verticut as necessary, dilute the organic matter with sand topdressings.

Turfgrass Research at Mauritius


I was at Mauritius last month and visited most of the golf courses on the island. Mauritius has some of the most visually striking golf courses I have ever seen. I was surprised (and impressed) to see beautiful evaluation plots of grass at Paradis Golf Club, where course superintendent Ajaye Ladsawut is maintaining a nursery with different varieties of bermudagrass, seashore paspalum, and even some zoysiagrass. This is an amazing site for turf research plots, right at the base of a World Heritage Site, the rugged Le Morne Cultural Landscape (see below) which served as a shelter for runaway slaves. The grasses are being grown on two different rootzones, a dark rock sand (foreground above) and a calcareous coral sand (background above); the purpose of the grass evaluation nursery at Paradis Golf Club is to determine which grasses perform the best, and in what soil, for a new course in planning stages now and for possible course improvements at Paradis.


The Paradis Golf Club has seashore paspalum (originally from Durban CC) on the greens, a local bermudagrass is the primary species on tees and fairways, and there are also areas of blue couch (Digitaria didactyla), St. Augustine or Buffalo grass (Stenotaphrum secundatum), Zoysia matrella, and Sporobulus. The irrigation water is rather high in salt as the course sits right on a lagoon, but all these grasses manage to grow well.


The grass evaluation plots at Paradis are very well-maintained and are given nearly the same maintenance treatments as the grass on the golf course. The Bel Ombre paspalum is from a nearby golf course and has a slightly different growth habit and stolon color compared with the Durban CC paspalum on the greens at Paradis.


This is a seashore paspalum fairway (with patches of bermudagrass at right) on Ile aux Cerfs, also at Mauritius. One of the most challenging things in the management of seashore paspalum is to keep other grasses out. The native bermudagrass here is quite salt tolerant and grows vigorously. Rock salt is used here to control most weeds in the seashore paspalum, and the use of salt is a good strategy for weed control in seashore paspalum when soil conditions allow it. Seashore paspalum is beautiful but it can also be a high maintenance grass and will tend to be overtaken by other grasses when grown without intensive and expensive maintenance.

General (and Technical) Presentation Tips

Present We have all been to conferences or seminars and have seen excellent presentations; we have also seen presentations that were not interesting or somehow failed to convey much useful information to the audience. Because I regularly attend conferences about turfgrass, I take a special interest in the subject of presentation design and delivery, and wish to recommend a few books and a particular website to those who also have an interest in effective communication.

I am particularly fond of these three books by Dr. Edward Tufte, statistician, noted expert on the visual display of data, and professor emeritus at Yale University. These books are:

The Visual Display of Quantitative Information

Envisioning Information

Visual Explanations: Images and Quantities, Evidence and Narrative

Dr. Tufte has also written an essay that anyone who gives presentations should read, study, and keep for occasional reference. This is, of course, The Cognitive Style of PowerPoint.

MakingPresentationsThatStick.pdf (page 1 of 4) Another book about ideas and how they are remembered is Made to Stick by Chip and Dan Heath. This book explains the six principles of ideas that are remembered (sticky ideas) and at the Made to Stick website there are additional free downloads, including one on how to make your presentation stick.

When it comes to the design of the presentation itself, and the visual materials that may accompany it, I suggest reading slide:ology by Nancy Duarte. This book provides all the information necessary to create great slides.

Garr Reynolds is the author of Presentation Zen and the blog of the same name. This blog is a wealth of information about presentation technique, effective communication, good design, and examples of good and bad presentations. Reynolds has written about making effective presentations of technical material, which I think is especially important for scientists and for those in the turfgrass industry as well.

If you are interested in making the best presentation possible the next time you are on stage, I would read the Presentation Zen blog and would look into the aforementioned books. Do you have other resources that have been especially helpful to you? For even more about data presentation, statistician John Tukey's Exploratory Data Analysis (1977) is also an excellent resource, as is his chapter on Some Graphic and Semigraphic Displays from Statistical Papers in Honor of George W. Snedecor (1972).