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June 2011

Turfgrass Archaeology

soil profile of putting green2

This soil profile, showing how the soil has been modified after about 70 years of management as a golf course putting green, is absolutely fascinating. This photo is from a course at Sydney, Australia. Because this hole is now closed for a complete renovation, the superintendent decided to make some archaeological researches by digging down to the original dune sand that the green was built on. Click on the photo above or click here to get a full size image for closer inspection.

Starting from the bottom of the profile, we can see the clean sand that is the original dune, meters deep, that the green was planted on. Moving up, we see darker material at the base, this probably being some organic material that was mixed in the soil at the time of planting the green. Then we start to see distinct layering, dark and then white bands moving horizontally across the profile; these would be the bands of sand topdressing laid down at annual renovations, as the scarifying-aerifying-topdressing activity is often referred to in Australia. And we start to see aerification holes, filled with sand from decades ago, still providing that vertical channel through the soil profile that is so critical to rapid air and water movement. 

Moving up through the central part of the profile we can see perhaps a change of topdressing sands, perhaps some periods when more coring was carried out, and less topdressing sand was laid down, and then nearer the surface we see even more coring holes filled with sand, and what appears to be a higher organic matter content, still diluted with sand, but perhaps less so than lower in the historical profile.

This profile is one of the most interesting things I've seen on a golf course, and it helps to remind me that the maintenance work we do on a daily basis will have an impact on how water, nutrients, and air (and consequently roots) move through the soil profile for years to come.

How Much Potassium Does Turfgrass Need?

Soldat_potassium Potassium is the mineral element found in the second-highest concentration in turfgrass leaves; only nitrogen is at a higher concentration. But how much potassium fertilizer is enough? Dr. Doug Soldat from the University of Wisconsin wrote a post for the Turf Diseases website entitled How I'd Manage Potassium on Cool-season Turf, and he has expanded on that in an excellent article in the May/June issue of The Grass Roots.

Dr. Soldat makes a quick review of when and how potassium is likely to provide improved cold, heat, drought, and wear stress. You might be surprised to find that the research results aren't very strong or conclusive in supporting the idea that high levels of potassium fertilization confer these increased stress tolerances to cool-season grasses. There is no doubt that potassium is an important mineral element, but if there is already enough potassium available to the grass, adding more doesn't seem to have much of an effect. For example, we can read in textbooks that more potassium will lead to a more extensive root system, but is that really the case? 

Woods-turfnet-k-roots Does potassium fertilizer really increase roots?, I asked, in this article from TurfNet Monthly. My conclusion was that potassium fertilizer will do nothing to increase roots, and in fact may actually cause a decrease in rooting, unless the potassium was being applied to correct a potassium deficiency. Potassium application to turfgrass is likely to increase rooting only when it eleminates a potassium deficiency. I would classify a turfgrass soil as requiring additional potassium at about the 50 ppm level using the Mehlich 3 soil test extractant. If the soil is less than 50 ppm potassium, we might expect some response from a potassium fertilizer application. If the soil has more than 50 ppm potassium, the grass can almost certainly get all the potassium fertilizer it requires from the potassium that is already in the soil, and potassium fertilizer would be unlikely to influence turfgrass performance. 

Australian Turfgrass Conference & Associated Studies

Brisbane_redlands In the past two weeks I've been to Brisbane, Adelaide, Melbourne, and Sydney. I visited the Redlands Research Station in Queensland where there are numerous experiments about turfgrass and where one can find an extensive collection of turfgrass demonstration plots. 

Then I went to Adelaide for the Australian Turfgrass Conference. The AGCSA invited me to speak about plant nutrition, warm-season grass selection, and the management of turfgrass in difficult growing environments. In the plant nutrition presentations, I discussed the role of nitrogen in controlling the energy production of turfgrasses. The net CO2 uptake is controlled by light, temperature, water status of the plants, and the nitrogen levels in the leaves. Light and temperature are largely out of the control of turfgrass managers. Water and nitrogen, however, can be controlled precisely to modify the photosynthetic rate of the grass, and consequently the growth rate and performance of the turgfrass.

Conference I also spoke about the types of grasses that perform well in Southeast Asia and suggested why certain grasses perform well and others do not. One thing I have noticed in my travels across Australia is the variety in turfgrass species that are used to produce fine sporting surfaces. I've seen golf courses or sports fields of kikuyugrass, bermudagrass (green couch), creeping bentgrass, colonial bentgrass, fine fescue, perennial ryegrass, mixed in with Axonopus compressus, Poa annua, and Digitaria didactyla (blue couch). Although the climate in Southeast Asia is a bit extreme with high temperatures year-round and relatively low sunshine, there is an advantage to that when it comes to grass selection for sports turf, as there are really only a few species than can be used to produce the desired playing conditions. In Australia, the climate throughout the year is much more variable, and consequently more grass species can be used.


I met old friends and made new ones at this conference. Brian Whitlark from the USGA Green Section was also here to speak at the conference. I'm happy to report that our team in the AGCSA/Toro Scramble made eight birdies and no bogeys on a windy and cold morning at Adelaide Shores during this fun networking event.

Talk_melbourne I had a great time speaking with conference delegates and have learned a lot as I have traveled around Australia to see how turfgrass surfaces are prepared for a variety of sports here. From the sports fields at the University of Queensland to the wickets at the Adelaide Oval to catching an AFL game at the Melbourne Cricket Ground, from the Mornington Peninsula to Melbourne's sandbelt courses to the three courses I visited at Adelaide, I have had a chance to talk with turfgrass managers who are passionate about the same thing — producing the best possible surfaces. 


What Grasses Are Growing on Golf Courses in Thailand?

In 2006, ATC conducted a survey of the grass types on golf courses in Thailand. Surveys were sent to the more than 200 courses in Thailand, and 41 of the surveys were completed and returned. Data from that survey are shown in this table:

I've visited or played golf at 24 different golf courses in Thailand since January 1, and I thought it would be interesting to summarize the different grass types that are being grown on these courses. Of the 24 courses I've been to this year, 79% have hybrid bermudagrass on the greens, 4% seashore paspalum, and 17% use Zoysia matrella. On fairways this year, 38% of the courses I've visited have seashore paspalum, bermudagrass and Zoysia matrella are each on 29% of the courses, and a native grass mixture is on 4%. 

green fairway of Laguna Phuket

I like the native grasses on the fairways because of reduced fertilizer and water requirements and the paucity of any pests on Zoysia or Axonopus in Thailand. Not only do these fairways have great color (see at right), they also have great playability.

At Thailand there has been rapid adoption of new bermudagrass cultivars. Nineteen of the courses I visited this year have bermudagrass on the greens, and of those there are two with Miniverde, four with Novotek, five with Tifdwarf, and eight with TifEagle.

Many of the older courses in Thailand such as Royal Hua Hin (pictured below) and Royal Bangkok Sports Club use a fine-bladed Zoysia on the greens. This grass requires little maintenance and produces a fine playing surface for year-round play. One thing I don't see much of on zoysia greens is algae — the grass leaves provide such a dense cover of the ground and the irrigation requirements are such that algae never has a chance to gain a foothold.

zoysia green at Royal Hua Hin

I wrote more about warm-season grass selection and maintenance in this article for Golf Business Asia in 2008. But no matter what grasses are used at the courses in Thailand, I think you will find that the playing conditions across the country are consistently among the best in Southeast Asia. With an active golf course superintendents association (the Thai GCSA), regular educational events such as the Sustainable Turfgrass Management in Asia conference, and a steady stream of new golf courses being built and older courses being renovated, Thailand is an exciting place to study grass.


World Cities Plotted by Climatological Normals, June


This bubble chart shows 45 world cities plotted by average June temperature, June sunshine, and June precipitation. The plot for May had 46 cities; because Kota Kinabalu and Brunei have similar weather conditions and often overlap on these plots, I have elected to omit Brunei for clarity.

Compared with May, the cities in India have more rain and less sunlight as some monsoons begin, and New Delhi is really hot, hotter than Dubai, Phoenix, and Las Vegas! Hong Kong still doesn't have much sunlight but there is more than in May. And there is a big difference in transition zone cities such as Shanghai, Tokyo, Osaka, and Atlanta; by temperature and rainfall these cities are similar but during the month of June there is a lot more sunlight in Atlanta. We can also see why it is difficult to grow bentgrass in Atlanta. The temperature in June is similar to Hawaii or Florida but the summer is just getting started.