On the relative merits of Zoysia matrella vs. Paspalum vaginatum as a golf course turf in Rio de Janeiro

I have suggested (in this video) that the grasses likely to perform well as a golf course turf at Rio de Janeiro would be the same species that perform well in places like Hilo and Hong Kong. That is, manilagrass (Zoysia matrella) is likely to perform well in open unshaded areas and in scattered tree shade, and tropical carpetgrass (Axonopus compressus) is likely to perform well under tree canopies.

I was asked a question

When Hanse Golf Course Design was selected to design the course for the 2016 Olympic Games, the press release spoke of a “strong legacy component,” that the course would be an “example of sustainability,” and that the firm's proposal had “addressed the environmental sustainability directives for the Games.”

I was therefore pleased to learn that Zeon zoysia (a variety of manilagrass) was chosen for the tees, fairways, and rough at that Olympic project. According to Dr. Frank Rossi, consulting agronomist on the project, 88% of the grassed area will be manilagrass. The greens and the immediate green surrounds will be seashore paspalum (Paspalum vaginatum). Those grass species seemed like a fine choice for the climate of Rio de Janeiro.

That is because the manilagrass has good drought tolerance, a low nutrient requirement, few pesticide requirements in that climate, and has a slow growth rate, with less mowing required. For the “legacy” course that remains after the Olympic Games, good playing conditions can be maintained at minimal cost with 88% of the grassed area planted to manilagrass. Seashore paspalum is expected to require more water, fertilizer, pesticides, and mowing, so restricting it to 12% of the grassed area would be a better “example of sustainability” than if that species were planted on more of the grassed areas.

Last month, someone asked me why manilagrass was being used and suggested that perhaps it would have been better to use seashore paspalum across all areas of the course. I've been thinking about that question, and how to explain why I think that would be a mistake – or more specifically, why that would be a mistake if one is serious about the sustainability talk in the press release.

The short answer

This can only be answered in the context of what we want to manage.

  1. This course is to be an “example of sustainability”
  2. There is to be a “legacy course” to be maintained after the Olympics
  3. The operators of the legacy course should not be saddled with high maintenance requirements and costs

If we take these 3 points as what we are trying to manage, then there is no doubt that manilagrass should be planted on as much area as possible. Compared to seashore paspalum, manilagrass will use less water, less fertilizer, requires less energy cost for mowing, has fewer weed, disease, and insect pests, and will be considerably less expensive to maintain.

If one doesn't focus on those 3 points, and just wants grass that will grow fast, and must be intensively managed, without regard for the maintenance costs, then seashore paspalum becomes the choice.

The full answer, with plenty of supporting examples

First we consider the goals, and then look at examples and data that show why manilagrass is better able to meet the goals than is seashore paspalum.

What is the goal?

When choosing grasses for a golf course project, one must be sure that the grass can provide the desired playing conditions. Additionally, the R&A advise that:

Fertiliser and irrigation to be provided only as required to keep grass alive, not to present a lush and verdant course.

And GEO, in their Sustainable Golf Development guidelines, explain that:

sustainable grassing plans are based on the use of the most drought-tolerant and disease-resistant turfgrasses for the locality.

Gelernter et al. propose that progress toward sustainability can be measured by collecting data on maintained turf acreage, fertilizer and pesticide inputs, irrigation water use, and fuel and energy use.

How are manilagrass and seashore paspalum expected to perform in the categories outlined above? Manilagrass should require less irrigation and fertilizer, is more drought-tolerant and disease-resistant, will probably require less pesticides, and will almost certainly require less energy to maintain.

Seashore paspalum can grow faster than manilagrass, which can be a desirable trait at a project that is rushed for time, as media reports suggest the Olympics course is. But other than growing faster – a trait that is not associated either with high quality playing surfaces or sustainability – I fail to see an advantage to seashore paspalum.

An extensive show of examples, starting with irrigation

Manilagrass does not require irrigation in a climate such as that at Rio de Janeiro. That is, it doesn't die even when it goes weeks or even a couple months without irrigation.

Starting to get dry, like British Open dry. Nice that the zoysia will just come right back when the weather breaks. pic.twitter.com/QELQvSyB

— Albert Bancroft (@alban3074) August 27, 2012

Contrast that with seashore paspalum, which requires supplemental irrigation. The photos below are typical examples. At Siam CC in Thailand, seashore paspalum planted around bunker edges died, due to lack of water, and was replaced by bahiagrass (Paspalum notatum). At the Asian Turfgrass Center, seashore paspalum and manilagrass planted on the same soil, grown side by side, with irrigation withheld, produce completely different surfaces.

This blog post explains more, and I made a video showing where these grasses are found in the wild. When we see the natural environment in which seashore paspalum and manilagrass grow, it provides insight into what type of maintenance (and irrigation) requirements these grasses will have.

Mowing and costs

Because seashore paspalum requires supplemental irrigation, it grows more, and consequently requires more mowing. With manilagrass, there is a slower growth rate, generally, and irrigation is optional, thus allowing one to let the grass grow slowly with considerable reductions in mowing.

This case study of Banyan Golf Club in Thailand explains that planting zoysia to fairways and semi-rough made “it much easier to consistently produce the desired playing conditions at Banyan Golf Club without incurring excessive costs.”

I've often seen unirrigated manilagrass and it, like fine fescue fairways in Scotland, can be allowed to go dormant in drought. I've never seen seashore paspalum fairways allowed to go dormant.

There will be additional water costs in addition to mowing costs for seashore paspalum.

Diseases and insects and weeds

Manilagrass and seashore paspalum are both susceptible to insect damage, but seashore paspalum seems to be especially palatable to some insects. These photos were taken on the same day. Seashore paspalum was severely damaged by armyworms. Meyer zoysiagrass had no visible damage from armyworms.

Seashore paspalum can be quite susceptible to bermudagrass (Cynodon) invasion. Note also that the paspalum in the image below will not recover from such drought conditions. It hasn't just gone dormant – it has died.

Although this is primarily a visual issue, and not related to playability, if one does not remove the bermudagrass, it can completely overtake the seashore paspalum.

Of particular concern is the susceptibility of seashore paspalum to fungal diseases, especially dollar spot.

Manilagrass fairways at rough at Rio de Janeiro would require few if any fungicides; seashore paspalum, however, may require frequent fungicide applications to prevent dollar spot and other fungal pathogens.

At the Volcano Golf Course near Hilo, Hawaii, seashore paspalum also becomes infected by dollar spot.

More pesticide inputs are expected for seashore paspalum to control the weeds, insects, and diseases that can reduce turf quality. And if seashore paspalum were used rather than manilagrass, the grassing choice fails to meet the simple criterion given by GEO:

sustainable grassing plans are based on the use of the most drought-tolerant and disease-resistant turfgrasses for the locality

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