Response of Five Bermudagrass Cultivars to Simulated Shade Levels.

The use of bermudagrass (Cynodon dactylon L. Pers) as a sports turf in the Southeastern USA is desired mainly for its wear tolerance and recuperative ability. However, the lack of shade tolerance in bermudagrass cultivars may limit its use. This study aimed to investigate the response of five bermudagrass cultivars (‘Tifway’, ‘Patriot’, ‘Celebration’, ‘TifGrand’, and ‘TifSport’) under four light environments: full sunlight, 30, 60, and 90% simulated shade. Shade tents were built utilizing a PVC frame 2x2 m in size and 45 cm tall. Custom-made shade cloth for the desired shade levels was attached to the frames, including a “skirt” that closed partially three sides of the tent to avoid diffuse light from reaching the plots, and yet to promote some air movement under the tent through the open side. Pots 30 cm tall and 15 cm in diameter were prepared with a 10 cm gravel base layer and 30 cm soil mix according to the USGA recommendations for putting green construction, a commonly found sports fields rootzone mixture. Grass plugs from the five chosen bermudagrass cultivars were collected with a standard golf cup-cutter. After collection, plugs had the excessive soil shook and washed off, and roots were trimmed to a common length prior to transplant. Pots were acclimatized in a greenhouse where maintenance practices took place until a fully-grown stage with adequate turfgrass quality was achieved. Daily watering, and weekly topdressing with USGA sand, fertilization and mowing followed until pots were ready to be at field conditions. Pots were then moved to the Turfgras Research Unit in Auburn, AL and placed under tents with individual irrigation system to keep adequate moisture levels. Clippings were collected weekly with help of a wooden rack allowing the use of a reel mower set at approximately at 1.8 – 2 cm. Visual ratings for turf quality and cover, pigment extraction and analysis, and leaf morphology measurements were also performed. Clippings weight was not an ideal measurement for overall turf performance, most likely due to turfgrass etiolation and morphological changes under increasing shade levels. Turfgrass quality and cover were decreased by shade over time in the study. Turfgrass quality ranking for cultivars under 60% continuous shade after 10 weeks was: TifGrand > TifSport > Celebration ≥ Tifway > Patriot. Shade also interfered in chlorophyll A/B ratio especially due to changes in chlorophyll B. TifGrand and Celebration had the least turfgrass quality under full sunlight compared to other cultivars, which can be attributed to excessive seedhead production resulting in decreased turf quality.