Evaluation of novel techniques to establish and transition overseeded grasses on bermudagrass sports turf

Most professional turf in Virginia is comprised of bermudagrass (Cynodon dactylon L.) or (Cynodon dactylon x C. transvaalensis Burtt Davy) as a monoculture in summer and overseeded with perennial ryegrass (Lolium perenne L.) (PR) in winter, during bermudagrass dormancy. Two transitions are required in an overseeding program, fall establishment of PR and spring control of PR. During each transition, turf quality suffers as one grass dies or enters dormancy while another grass is promoted to fill voided areas. Field studies at various locations in Virginia were conducted to investigate methods of improving spring and fall transition. Bermudagrass green cover in August was influenced by duration of PR competition variably between three bermudagrass cultivars. For example, "Midiron", "Patriot", and "Riviera" bermudagrass required 218, 139, and 327 cumulative growing degree days at base 18.3 C (GDD) to reach 95% cover. Bermudagrass biomass was also positively correlated with increasing duration of noncompetitive GDD. Total nonstructural carbohydrates were not correlated to duration of PR competition. Novel application methods were invented and tested at Virginia Tech. Drip, sponge, and strip application methods were used to create patterns of PR control using selective herbicides. Controlling a portion of PR with these methods maintained acceptable turfgrass quality throughout the spring transition and improved bermudagrass cover 12 to 20%, speeding transition by 20 or more days. Efforts to improve PR establishment in dense bermudagrass suggest chemicals that injure existing bermudagrass can improve PR establishment, but cause unacceptable turf discoloration. Mechanical methods to disrupt the bermudagrass canopy had less effect on PR establishment than chemical treatments.