Quantifying a daily light integral requirement of a 'TifEagle' bermudagrass golf green

'TifEagle' bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy] is a fine textured hybrid bermudagrass used for golf course putting greens in the subtropical and tropical regions of the world. The growth and performance of TifEagle and other bermudagrass often decline in reduced light environments (RLEs). This study quantified a daily light integral (DLI; mol m(-2) d(-1)) required to maintain commercially acceptable TifEagle bermudagrass maintained under golf green conditions. Three levels of shade, none, low, and high (0, 41, and 92%), were applied to mature TifEagle bermudagrass during morning (sunrise to 1100 h) and afternoon (1500 h to sunset) hours, allowing full irradiance from 1100 to 1500 h to mimic a golf green situation where trees or structures are adjacent to, but rarely directly overhead. The study was performed for 8 wk in June to August 2001 and 2002. An average minimal DLI of 32.6 mol m(-2) d(-1) was needed to maintain commercially acceptable TifEagle turf quality (TQ greater than or equal to 7). Other plant responses measured included percentage lateral regrowth (RG), total shoot chlorophyll, and total non-structural carbohydrates (TNC). These responses declined significantly when the DLI less than or equal to 32.6 mol m(-2) d(-1). Differences in diurnal shade exposure occurred. High afternoon shade reduced TifEagle bermudagrass TQ, percentage lateral RG, shoot chlorophyll, and TNC by 3.0 rating units and 17, 39, and 27%, respectively, compared with no afternoon shade (NSA). High morning shade reduced TQ, percentage lateral RG, and shoot chlorophyll by 1.5 rating units and 11 and 16%, respectively, compared with no morning shade (NSM). Overall, afternoon shade applications were more detrimental to TifEagle bermudagrass growth and performance compared with morning shade.