A recent conversation about putting surfaces in Japan led to discussion of topdressing amounts and frequency.

The Greenkeeper 2018 has course maintenance summaries for 17 courses in Japan. I mapped the locations of those courses by zip code.

^{Map tiles by Stamen Design, under CC BY 3.0. Data by OpenStreetMap, under ODbL.}

All those courses have bentgrass greens. Eight of them reported the variety as Pencross, three as L-93, and the other varieties were:

• Penncross/L-93
• SR1020
• Penncross/Imperial/SR1019/L-93/Tyee
• 962/Crenshaw
• Penncross/L-93/Shark
• Penncross/L-93/007/Mackenzie

Except for the 962/Crenshaw and SR1020, I expect these additional varieties are the grass/es used for interseeding into a Penncross base.

The median annual rounds on these 17 courses was 40,255. The median annual topdressing amount was 7.7 mm. The median number of topdressing events per year was 17. The median N application was was 10 g/m² (2 lbs/1000 ft²). The median N for greens in the USA is 3.7 lbs/1000 ft².

Is there survey data for the average number of topdressing events on golf courses in the USA? I would guess the median course in the USA would topdress more than 17 times a year.

The median amount of sand applied on these courses in Japan is close to – actually, it is 25% more than – the 20.3 ft³/1000 ft² minimum recommended by Schmid et al. and is about half the amount recommended by O’Brien and Hartwiger.