Nitrogen and Plant Growth Regulator Influence on 'Champion' Bermudagrass Putting Green under Reduced Sunlight

Managing warm-season turfgrasses with reduced sunlight is challenging due to C-4 plant morphological limitations, such as reduced lateral stem growth. Adjusting cultural management practices, such as N and trinexapac-ethyl (TE) [4-(cyclopropyl-a-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester], application may benefit turfgrass performance when sunlight is reduced. Therefore, a 2-yr field study from 15 June to 15 September in 2006 and 2007 at Clemson University investigated the best management practices for sustaining a high quality 'Champion' bermudagrass [Cynodon dactylon (L.) Pets. x C. transvaalensis Burtt-Davy] putting green maintained at a 3.2-min mowing height under reduced sunlight. Treatments included full-sunlight, 55% full-day shade, TE (0.02 kg a.i. ha(-1) 2 wk(-1)), Fe (2.7 kg ha(-1) 2 wk(-1)), and N as liquid urea at 147, 293, and 440 kg ha(-1) yr(-1). Data collection included visual turfgrass quality (TQ), total clipping yield, clipping chlorophyll concentration, root total nonstructural carbohydrates (TNC), thatch accumulation, and thatch depth. Overall, Fe applications minimally impacted parameters measured. Increasing N rates linearly increased TQ when grown under full sunlight. Applying N at similar to 40% lower (147 kg ha(-1) yr(-1)) than the typical recommended rates for ultradwarf bermudagrass putting greens improved Champion TQ under reduced light compared to higher N rates. Applying TE resulted in a linear TQ increase for full sunlight and shade-grown Champion bermudagrass. Under reduced sunlight, a 15% chlorophyll concentration increase was noted for TE-treated plots compared to nonTE-treated plots. Shade reduced thatch accumulation 40% compared to sun-grown Champion, which suggests less aggressive cultivation practices are required for thatch control under reduced light. Champion bermudagrass did not provide an acceptable putting green quality when grown under 55% full-day shade, however, adjusting management practices enhanced Champion bermudagrass quality under reduced light.