‘TifEagle’ Bermudagrass Response to Growth Factors and Mowing Height when Grown at Various Hours of Sunlight

Application of growth promoters or inhibitors and mowing height adjustment are potential means of improving the growth and performance of TifEagle bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy] in a reduced light environment (RLE). A study was conducted in June to August 2001 and 2002 to examine the effects of growth factors and two mowing heights on TifEagle bermudagrass when grown at various hours of sunlight. Shade cloth (92%) was used at different intervals to obtain three sunlight hours, 12 h (0800–2000 h), 8 h (1000–1800 h), and 4 h (1200–1600 h), with an average 2-yr daily light integral (DLI) of 41.1, 35.5, and 22.1 mol m⁻² d⁻¹, respectively. Sunlight hours were split by growth factor applications and mowing height. Growth factors included trinexapac-ethyl [TE; 4-(cyclopropyl-alpha-hydroxymethylene)-3,5-dioxo-cyclohexanecarboxylic acid ethyl ester] at 0.0393 kg a.i. ha⁻¹ every 3 wk, gibberellic acid (GA) at 0.059 kg Gibberellin A₃ (GA₃) ha⁻¹ every 2 wk, additional nitrogen (+N) application of 24.5 kg N ha⁻¹ every 2 wk, and an untreated check. Turf was mowed at 3.2 or 4.7 mm daily. Acceptable turf quality (TQ) followed all growth factor treatments receiving the 12 and 8 h of sunlight, except GA. For the 4-h sunlight treatments, only plots treated with TE and mowed at 4.7 mm resulted in acceptable TQ. The +N applications increased percentage lateral regrowth (RG) of TifEagle bermudagrass by 7 to 10% compared with other growth factors. Across all sunlight treatments, TE increased total shoot chlorophyll by as much as 19 and 42% compared with untreated, +N, and GA-applied plots. The 3.2-mm mowing height increased total nonstructural carbohydrates (TNC) by 19% compared with TifEagle mowed at 4.7 mm. Growth factors, including TE, +N, or GA, did not improve TNC concentration. In a RLE, methods of improving the growth and performance of TifEagle bermudagrass include TE applications and raising the height of cut to 4.7 mm. Overall, the growth and performance of TifEagle bermudagrass reduced greatly in the 4-h sunlight treatments compared with 12- and 8-h sunlight treatments.