High Shoot Density Bentgrasses Need Topdressing
Increasingly we are seeing the high shoot density creeping bentgrass cultivars like the Penn "A" and "G" series being established on putting greens throughout Australia. It's obvious the popularity of these cultivars is due to their almost billiard table look and the ability to mow these cultivars at a low height of cut. In addition they appear to be more competitive against annual bluegrass than the older cultivars like "Penncross".
The major agronomic problem with these greens is the rapid rate in which thatch can accumulate. An excessive thatch layer on any creeping bentgrass green reduces their ability to tolerate environmental stresses including heat and drought. In addition, thatch mitigates or buffers ball roll thus reducing the ability to increase roll rapidly. Practices that minimise thatch accumulation are critical. Topdressing is one practice that is important in minimising/diluting the thatch layer. With these high shoot density cultivars a light weekly topdressing program is required. Less frequent topdressing just does not seem to cut it.
In a recent research paper out of Texas, they looked at controlling ultradwarf bermudagrass thatch with topdressing and found that light biweekly applications or twice yearly heavy applications were not effective in minimising thatch accumulation (1).
Although topdressing is only one practice that can help manage thatch, a weekly topdressing program will be needed to minimise thatch accumulation on high shoot density creeping bentgrass cultivars.