These photos from an abandoned golf course in the southern part of the Tohoku region of Japan are fascinating. They show clearly how three different species perform when they are not maintained for 18 months in that climate. From a consideration of the grass performance when abandoned, one can get a good idea of the maintenance requirements for the grass when it is being actively maintained.
These photos are provided courtesy of Mr. Norifumi Yawata, who kindly shared them with me along with some details about this site.
This site, formerly a golf course, has not been maintained for 18 months. One is essentially looking at what happens to 3 species of grass after 2 growing seasons (2013 and 2014) with no maintenance.
The greens were creeping bentgrass. The tees and the collar immediately around the greens were (and still are) korai. Korai is Zoysia matrella – the common name is manilagrass. Everywhere else, the fairways, the roughs, and so on, are noshiba. Noshiba is Zoysia japonica – the common name is japanese lawngrass.
In these photos we see the characteristics of these grasses as they are adapted to this environment. Creeping bentgrass on the green surfaces has been overtaken by weeds. Clearly, creeping bentgrass in this environment seems to require mowing and supplemental irrigation and fertilizer and probably some pesticides in order to persist. It dies quickly without those inputs, or at least it becomes thin, with many voids in the turf that allow for invasion by other species.
The photo above shows a sand bunker in the foreground. Then comes some noshiba with the characteristic autumn symptoms of the wonderfully-named elephant's footprint disease caused by Rhizoctonia cerealis. At the edge of the green surface itself is a band of korai, finer-bladed than the noshiba. And then the green, now a weed patch.
The korai and the noshiba both persist at this site for at least two years. It looks like some mowing of the korai and noshiba would get these surfaces back to acceptable condition by next summer. But the bentgrass is beyond saving. Because the korai and noshiba persist, it is evident that they survive without irrigation, and without fertilizer, and that the mowing, and perhaps some weed control, are all that are required to keep them at a minimal level of performance.
There are various implications of these observations on weed invasion of abandoned turf. This supports something I've written about before: for large areas of maintained turf, it makes sense to use a grass that won't die. Then one will be assured that with minimal maintenance, the quality will be acceptable. And with intensive maintenance, that grass that won't die will be able to tolerate every type of aggressive maintenance, allowing one to produce high performance turfgrass surfaces.
In this case, and at most golf courses in Japan, this good practice of grass selection is used. The creeping bentgrass area is small, less than 5% of the maintained turf area. So the grass that dies, the grass that requires intensive inputs, is planted only on a minimal area. The grasses that don't die, and that require relatively fewer inputs of irrigation, and fertilizer, and pesticides, and mowing – in this climate these are korai and noshiba – are used on more than 95% of the maintained turf area.