Seasonal Cultural Management Practices for Aging Ultradwarf Bermudagrass Greens in the Subtropics: I. Nitrogen and Potassium Management

Bermudagrass cultivars [Cynodon transvaalensis (L.) Pers. X Cynodon dactylon (Burtt-Davy)] with more decumbent growth habits referred as “ultradwarfs” have been released for use on golf course greens and tees as an alternative to standard bermudagrass varieties that have been used for over 40 years. Little research information is available on long-term ultradwarf management requirements in subtropical environments. Therefore, a four-year experiment was conducted in South Florida on a United States Golf Association specified green to determine the effects of nitrogen (N) fertility and N to potassium (K) ratios on quality, growth and performance of three commercially-released ultradwarfs (‘Champion’, ‘TifEagle’, and ‘FloraDwarf’). For all three cultivars, fertilizing at 879 kg N ha^-1 yr^-1 resulted in acceptable turfgrass quality with mean tissue-N and K concentrations of 3.1 and 1.4%, respectively. Over the four-year experiment, leaf tissue-N and K were present approximately as a 2:1 ratio regardless of N rate and N:K ratio applied. As the ultradwarfs aged, fertilizing with 586 kg N ha^-1 yr^-1 was adequate. It appears that Champion and TifEagle have different mechanisms for increasing aboveground growth and had better quality and growth characteristics than FloraDwarf. This research documented the need for adjusting fertilization as the green ages and for the ultradwarf cultivar maintained.