Viridescent - the Asian Turfgrass Center blog

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.

Sodium Chloride for Weed Control

Another article about sodium chloride applications as a method of weed control in seashore paspalum has been published in Weed Technology. This research was done at Hawaii by Dr. Jim Brosnan, and I did some additional testing at Thailand and helped with the paper entitled "Sodium Chloride Salt Applications Provide Effective Control of Sourgrass (Paspalum conjugatum) in Seashore Paspalum Turf". Granular applications of sodium chloride at a rate of about 50 g m^-2 can cause severe damage to many weeds without causing phytotoxicity to seashore paspalum. In our research at Thailand, we first wet the leaves of the grass, then apply granular sodium chloride (table salt) and allow it to sit on the leaves of the grass. Because the leaves are wet, the salt will stick to leaves, as shown below, with salt applied to seashore paspalum (variety Salam) mowed at 15 mm. In our experiments, we see no phytotoxicity to the seashore paspalum, but the same rate of sodium chloride applied to bermudagrass or carpetgrass (Axonopus compressus) or to some broadleaf weeds will cause severe phytotoxicity or plant death.

The photo above shows sodium chloride crystals sticking to the wet leaves of a seashore paspalum fairway turf. If salt is used to control weeds in seashore paspalum turf, I think it will work best if applied when the weeds are still small. If weeds are allowed to proliferate, and sodium chloride is used to control the larger patches of weeds, then unsightly yellow patches will occur all over the turf. As with any weed control program, it is important to catch the weeds early. Earlier this week I was at Mauritius and visited Le Touessrok Golf Course at Ile aux Cerfs (see below); this is a seashore paspalum golf course where salt is regularly used to control bermudagrass (Cynodon spp.), St. Augustine grass (Stenotaphrum secondatum), and broadleaf weeds from encroaching into the seashore paspalum turf. One thing to remember of course is that too much sodium in the soil can cause problems with soil structure in clayey or silty soils. Sodium chloride applications may work best on sandy soils, where there is little chance of any soil structural problems.

Turfgrass at Dubai

I was at Dubai this week to see some golf courses and to learn more about turfgrass management here. There are many camels in the desert -- these ones are just outside the Al Ruwaya golf course at The Tiger Woods Dubai, which I visited for two days. The course looks spectacular. Three holes are completely grassed now, and the scale of the project is really mind-boggling. I was there in July of 2008 when rough shaping was just underway. What last year was just a vast expanse of sand now looks like a golf course, and one that will be a thrill to play. With huge grass nurseries, landscape materials being installed in abundance, an incredibly complex irrigation system being put together hole-by-hole, and the creation of such a beautiful course in the middle of the desert, this project is fascinating. The grow-in superintendent at Al Ruwaya is Cameron Thompson, who was previously at Amata Spring Country Club in Thailand.

Most of the courses at Dubai use hybrid bermudagrass, as on the Majlis course at Emirates Golf Club, site of the Dubai Desert Classic. But seashore paspalum can also be used at Dubai, as on the par 3 course at Emirates Golf Club shown above. Water is obviously an expensive resource in the desert, and golf courses use treated effluent water to irrigate the turfgrass, in some cases using a reverse osmosis plant to further purify the water before it is applied to the grass. Because of seashore paspalum's high salinity tolerance, salt is sometimes used to control weeds in the turf, and that practice was being employed on the par 3 course at Emirates Golf Club. Application of granular salt at a rate of about 50 g m^-2 can provide control of some grassy and broadleaf weeds without causing phytotoxicity to seashore paspalum.

The bermudagrass golf courses at Dubai are usually overseeded with perennial ryegrass during the winter months. This is The Els Club earlier this year when the perennial ryegrass was the primary playing surface. Because of the heat during the summer months (temperatures above 40°C are common), little golf is played, but during the winters the weather is quite clement and golf courses at Dubai are busy. The bermudagrass grows slowly at Dubai during the winter, nearly reaching dormancy, and the perennial ryegrass surfaces then provide a playing surface that can tolerate the heavy traffic during the winter months.

Can Sodium Chloride Control Weeds in Seashore Paspalum Turf?

Many new golf courses in Southeast Asia choose seashore paspalum (Paspalum vaginatum) for their grass, and some golf courses, when renovating, are changing to seashore paspalum. One of the challenges in managing seashore paspalum turf is the control of weeds. There are not many herbicides that can be used without damaging seashore paspalum. For control of weeds such as goosegrass, there are no herbicides labeled in the USA for use on seashore paspalum. I worked with Dr. James Brosnan on a project to investigate sodium chloride (NaCl, or table salt) applications for control of weeds in seashore paspalum turf. Our article, Efficacy of Sodium Chloride Applications for Control of Goosegrass (Eleusine indica) in Seashore Paspalum Turf, was published in the recent issue of Weed Technology.

Because seashore paspalum has a high salinity tolerance, it may be able to tolerate salt applications that would be toxic to weeds. In our study, we looked at sodium chloride application rates of 49 g m^-2, applied every seven days for three consecutive weeks. This rate of sodium chloride application did not damage the seashore paspalum, but it also did not provide effective control of goosegrass; the sodium chloride applications resulted in slightly more than 50% control of the goosegrass eight weeks after treatment. The published study was conducted in Hawaii, and the treatment that provided the best control of goosegrass was MSMA, but the MSMA applications caused phytoxicity on the seashore paspalum.

Another experiment was done to look at control of Paspalum conjugatum (some common names for this plant are sourgrass, carabaograss, or hilograss) in seashore paspalum turf. Our article about this experiment will be published soon in Weed Technology, and we found that there was effective control of the weedy grass with the same application rates of sodium chloride (sequential applications of granular sodium chloride at 49 g m^-2).