Shade Response of Bermudagrass Accessions Under Varying Management Practices.

The development of shade tolerant cultivars, specifically Tifgrand and Celebration, has shown the potential of bermudagrass, Cynodon spp., to persist in the tree dense landscapes of North Carolina. Previous research suggests that a reduction in nitrogen fertility rates, increased mowing heights, and the application of plant growth regulators (PGR) can reduce the symptoms of turfgrass stress grown in low light environments. In this study, two South African bermudagrass accessions (WIN10F and STIL03) and three standard cultivars (Celebration, Tifgrand and Tifway) were compared under these management practices for their ability to grow under 63% shade. The experimental design was a strip-strip-split plot where the main plot factor was genotype, the two strip plots were mowing height and application of trinexapac-ethyl, and then plots were split to incorporate fertility rates. The variables measured were whole-plot decline, cup-cutter recovery, divot recovery and normalized difference vegetation index (NDVI). Plots were evaluated weekly for each response variable over the course of 12-weeks. Based on preliminary data, differences were observed between genotypes across all response variables and rating dates. Celebration, WIN10F and STIL03 showed better recovery (cup-cutter and divot), reduced decline and greater NDVI values than Tifgrand and Tifway (P<0.05). Differences in PGR and mowing height treatments were observed, but varied across rating periods. Early on, the application of trinexapac-ethyl and increased mowing heights provided some benefit in reducing the impacts of shade stress. However, the persistence of shade and the waning growing season reduced the overall effects of these management practices. The interactions between genotype x PGR and entry x mowing height suggests that, although these cultural practices may provide a reduction in the symptoms of shade stress, the management recommendations are dependent on the genotype and its environment.  The development and implementation of specific management plans for certain varieties will help bermudagrass become a more prominent turfgrass for low light conditions.