Putting Green Surface Firmness as Affected by Bentgrass Cultivar and Cultivar Blends.

                Golf course managers continue to place increasing emphasis on management practices to promote ideal putting green surface firmness. Newer bentgrass cultivars have been bred to maintain high shoot densities at low mowing heights and superior summer persistence. Although these cultivars provide improved performance characteristics they also possess substantially higher shoot densities than prior generations, which may result in increased surface organic matter (OM) accumulation and a propensity for softer surface conditions without sufficient cultural management. A novel surface firmness measurement device, the Tru-Firm, was recently introduced by the United States Golf Association to monitor putting green conditioning practices. A field study measured the shoot density, surface, 0-25 mm, OM content and surface firmness as measured with the Tru-Firm for fifty bentgrass cultivars and cultivar blends one full growing season following planting. Shoot densities ranged from 18-40 shoots in², OM content ranged from 253-678 g kg^-1 and surface firmness ranged from 0.350-0.598 in. Although there was a tendency for higher OM contents with cultivars possessing high shoot densities this did not correlate well with surface firmness. The relationship between surface firmness, shoot density, and surface OM content continues to be complex and requires further long-term examination.