Viridescent - the Asian Turfgrass Center blog

Sunshine, Zoysia, and Grass Performance in Asia

There are four grasses in the image above (click on it to get a larger view). We are looking at Tifeagle and Novotek (both are Cynodon hybrids), Sea Isle Supreme (Paspalum vaginatum), and a fine-bladed zoysia, probably Zoysia pacifica. This is a test on a shaded green in Manila. The green is maintained for seashore paspalum. The seashore paspalum can handle this shade, although it has a relatively coarse leaf blade compared to the zoysia. Both types of Cynodon fail to produce an acceptable putting surface in this type of shaded condition under which both seashore paspalum and zoysia can produce a good stand of turf.

In fact, this zoysia produces a really superb putting surface, as seen at right, a photo I took on the 18^th green at Wack Wack Golf and Country Club during last week's Philippine Open. It requires very little in the way of fertilizer, few pesticides, and is able to tolerate the low sunshine levels and tree or building shade that can cause Cynodon, with its higher light requirement, to fail. Wack Wack recently underwent a renovation and the Club made a wise choice to keep the native zoysia on greens and the native carpetgrass everywhere else. There are beautiful mature trees across the property, and other grasses would not produce such fine surfaces in these low light conditions, but the zoysia and Axonopus thrive.

Many people ask me "what type of zoysia is that?" My best answer is that it is probably a type of Zoysia pacifica (previously called Zoysia tenuifolia), and I base that on a paper published in 2005 by Akamine et al. in volume 33 of the Journal of the Japanese Society of Turfgrass Science entitled "Morphological Characteristics of Zoysia tenuifolia Willd." In the research project reported in that paper, Akamine et al. found that Z. pacifica leaves are folded in the sheath, as compared to Z. matrella leaves which are rolled in the sheath. Upon close inspection, I found that the fine-bladed zoysia from the greens at Wack Wack has folded leaves, while the leaves of a typical Zoysia matrella from Japan were rolled.

For more information about sunshine, shade, turfgrass performance in Asia, and links to a lot more information about assessing the sunshine hours close to your location, here is a video I've recorded with Dr. Larry Stowell from PACE Turf about light.

Calcium for Turfgrass: is there enough in the soil?

The answer, almost certainly, is yes. These calculations of how much calcium the grass uses, compared to how much plant-available calcium is in the soil, leave little doubt that there is almost always more than enough calcium in the soil to meet the needs of the grass.

How much calcium does grass use?

Let's take a turfgrass site at which clippings are removed, and estimate how much calcium is removed, or harvested, in one year. A reasonable estimate for annual clipping yield of maintained turfgrass is about 400 g m^-2. A reasonable estimate for calcium in the dry matter of turfgrass clippings is about 4500 ppm = 4.5 g kg^-1 = 0.45%. So if we harvest, over the course of a year, 400 grams of clippings from each square meter, and if those clippings contain on average 0.45% calcium, then the mass of calcium harvested from one square meter each year is:

400 g x 0.0045 = 1.8 grams of calcium removed each year

How much calcium is in the soil?

We've just calculated that in the situation where we remove the clippings from a maintained turfgrass area, we may be removing about 1.8 grams of calcium from each square meter each year. Let's now imagine that our root system is 10 cm deep, and that the bulk density of the soil is 1.5 g cm^-3. In one square meter, then, to a depth of 10 cm, we have a volume of 100 L, and a mass of 150 kg. Let's say this is a sandy soil, with a relatively low cation exchange capacity, and that the plant-available calcium (the calcium that is in soil solution and on cation exchange sites) is at a concentration of 400 ppm = 400 mg kg^-1. How much calcium is that?

150 kg of soil x 400 mg/kg = 60,000 mg of calcium = 60 g of calcium

Three Decades

That's how long it would take, 33.3 years, to be precise, for the grass to use 60 grams of calcium if harvested at the rate of 1.8 grams of calcium per year. There is much more calcium in the soil than is required for healthy turfgrass, even in soils that have relatively low amounts of calcium.

World Cities Plotted by Climatological Normals, February

February is another good month, on average, to grow grass in Bangkok, Chennai, Colombo, and Mumbai. Why? With average temperatures more than 25°C and sunshine well above 200 hours for the month, the growth of warm-season grasses can easily be controlled by turfgrass managers through adjustments in the amount of water and nitrogen applied. 

Hainan Island is sometimes referred to as the "Hawaii" of China, but Sanya is considerably cooler and has a lot less sunshine than does Honolulu in February. For about six months of the year, Sanya is a lot more like Hilo than Honolulu, and that means slightly cooler temperatures and significantly less sunshine. 

Why "Liquid" Fertilization is Better Terminology than "Foliar" Fertilization

When applying fertilizer to turfgrass plants, there are two general types of application: liquid and granular. Granular products are applied in a dry form, while liquid products are applied as a spray application.

The term foliar fertilization is often used to describe liquid applications made to the leaves, or foliage, of turfgrass. But this can be misleading,with the implication that all the applied fertilizer is being taken up by the foliage. 

The reality is that only about 50% of the fertilizer applied to turfgrass foliage enters the plant through the leaves. And in many cases much less than 50% is absorbed by the leaves. Recent research by Branham et al. found that 14 to 37% of the applied nitrogen was taken up by turfgrass leaves in Illinois. Research at Arkansas by Stiegler et al. found uptake of 36 to 69% of foliar-applied nitrogen. These results are similar to the experimental results of Professor Jörg Schönherr who has done extensive research into foliar uptake of nutrient ions. Uptake is the highest at 100% humidity, so once the liquid solution has dried on the leaf, foliar uptake of the applied nutrients ceases. 

Even with the limited foliar uptake, I still prefer liquid applications to granular applications. With liquid applications, precise doses of nutrients can be spread evenly at low rates to all areas of the sward. It is impossible to get such even distribution of nutrients when applying granular products. 

When I was the superintendent at Shanghai Links, we made liquid fertilizer applications to all areas of the course as the main source of nutrients. We would allow the fertilizer to dry on the leaves, so we would get some uptake by the foliage, and we would then apply enough water to rinse the remaining fertilizer from the leaves and into the upper reaches of the soil, where the remaining nutrients could be absorbed by the roots.  

What's the Most Accurate Way to Measure Available Nutrients in the Soil?

Have you seen this picture before? I used this photo in the announcement for turf science seminars I gave at Japan last winter, and a golf course superintendent asked me this week about what is shown in this photo. This is a cation exchange membrane in general, and is specifically a PRS (Plant Root Simulator) probe from Western Ag Innovations. In my research at Cornell University, I used these exchange membranes to measure potassium flux in the soil. 

The results of this experiment were summarized in a paper we published in Applied Turfgrass Science. Exchange membranes are quite sensitive to changes in nutrient supply, and one could make a strong case for exchange membranes being a more accurate way to measure the really available nutrients in the soil compared with conventional soil testing techniques. Potassium supply to the roots, for instance, is affected by the activity of K⁺ in soil solution, leaching, soil temperature, soil water content, root uptake of K⁺, release of K⁺ from mineral forms in the soil, and other contributing factors. Exchange membranes, by measuring the nutrient flux over time, are able to capture much of the true variabiability in nutrient supply, similar to what grass roots would experience.

In our experiment, we found that the very sensitivity and accuracy of the exchange membranes makes them less practically useful than a conventional soil test in predicting whether potassium should be applied or not. To summarize the results of our experiments with cation exchange membranes, we found that:

1. Potassium supply increases when potassium fertilizer is applied.
2. The effects of potassium fertilizer can be long-lasting, even in a sand with low CEC (1.2 cmol_c kg^-1). We detected increases in potassium supply rate six months after an application had been made. I think most people would expect the potassium to leach or otherwise have no effect on supply rate six months after application in a low CEC sand.
3. Potassium supply rate can be sufficient to meet plant requirements in many sands because of potassium release from mineral forms in the soil.

World Cities Plotted by Climatological Normals, May

Last week I created a bubble chart showing seventeen world cities where warm-season (C₄) grasses are usually grown. The cities were plotted by average annual temperature on the x-axis, annual sunshine hours on the y-axis, and the size of each city's "bubble" on the chart was proportional to the city's average annual rainfall.

I have now made additional charts, with the number of cities in the dataset expanded to 46 to give a broader picture of the variability in climatological normals. And I have plotted the data on a month-by-month basis for a more detailed look at how the temperature, sunshine, and rainfall vary throughout the year.

Click the image above to view the bubble chart at a larger size. All data used to generate these plots are from the climatological normal tables for world cities as posted on the Hong Kong Observatory website. The bubble charts were created using the ggplot2 package in R.

I find it interesting to see how the average weather data for different cities change throughout the year. Of the 46 cities plotted here, Hong Kong stands out as having relatively little sunshine (on average) in the month of May. And in cities such as Tokyo and Osaka and Shanghai, where warm-season grasses are almost always used on fairways, the golfing season is well-underway but the temperatures are still too low for the optimum growth of warm-season grasses.

I think there is a lot of information in these plots that turfgrass managers may find interesting. As an example, Miami and Hong Kong have nearly the same average temperature in May, but Miami has more than twice the sunshine hours. This is the season when intensive cultural practices are done to control organic matter in bermudagrass greens in Florida; from looking at the bubble chart above it is obvious that the recuperative ability of bermudagrass at Hong Kong is probably much less in an average May than it would be at Florida. 

At which month is the temperature and sunshine at Tokyo the same as Singapore? How does this bubble chart change during the monsoon season in India? And does the sunshine at Hong Kong ever rise to the level of Miami? I'll post a new chart each month to show how the average weather changes in these cities over the course of a year.

New Information on Diseases and Cation Exchange Capacity

I've been really busy in the past month, returning to Thailand after the exciting Masters Tournament, traveling to Singapore, Vietnam, and Sri Lanka, studying, and writing. Thanks to @daisukeiw who sent me the image above of the layout for my new series in Golf Course Seminar magazine. Pitchcare Oceania have just published a panel report on cation exchange capacity (CEC) and have featured some comments from me about CEC in sand rootzones and how it can be estimated most accurately by using an equation in which the only variables are soil pH and soil organic matter content.

I've also made some international updates to the Turf Diseases website. Some of my recent posts on that site are:

Large Patch Resistance of Zoysia?

A Cornucopia of Disease in Southeast Asia

Healthy Grass = Little Disease

Potassium, Hokkaido, and Snow Mold

Turfgrass Diseases in India

What is the Most Interesting Disease in the World?

Mites, a Corpse Plant, and Native Grasses

Large Patch on Zoysiagrass

More About Seashore Paspalum

A Most Unsightly Disease

The Wow Factor, Seashore Paspalum, and Dollar Spot

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?

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.

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

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

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.