Perennial ryegrass (Lolium perenne L.) turf was grown under light-emitting diode (LED) lamps at different color temperatures (5,000 K [dominant wavelength: 450 nm] and 2,700 K [dominant wavelength: 600 nm]) for different irradiation times (8 and 4 h/day). Plants height were recorded, and all plants were clipped to a height of 20 mm weekly. The plants were harvested at 28 days after treatment. The dry weights of the clippings, tops, and roots, numbers of tillers and leaves, and degree of reddening at shoot base were measured. The total dry weight significantly increased, as did the photosynthetic photon flux density. The total dry weight was four times heavier under supplemental lighting (5,000 K 800 μmol 8 h) than under control conditions (5,000 K 0 h and 2,700 K 0 h). Significantly greater vertical elongation was noted at 2,700 K than at 5,000 K, indicating that supplemental lighting at 5,000 K suppresses upward elongation. The numbers of tillers and leaves were greater at 5,000 K, indicating accelerated growth and shortened curing. These data imply that 5,000 K supplemental lighting is effective for forming dense turf and early recovery from trampling and other damage.

Grass levees in the Seto Inland Sea region, composed mainly of Zoysia japonica Steud. cultivar ‘Asagake’, are mown three times a year, in May, July and September. We studied replacing the July mowing with a single application of a herbicide, bispyribac sodium salt solution. In 2016, there was no significant difference in the multiplied dominance ratio of grass leeves (m³/m²), [plant community height (m)×coverage (m²/m²)] in September between herbicide application from early June to late July and the conventional July grass cutting. In 2017, the community height was almost the same between herbicide application from late June to late July and the conventional July grass cutting. However, the multiplied dominance ratio (including the control) increased to 2.4 times the 2016 value owing to the dominance of cogongrass [Imperata cylindrica (L.) P. Beauv.], and the coverage of Z. japonica declined. The results show that substituting herbicide for mowing in July is possible when I. cylindrica is sparse during spraying.