Picture 1. TifEagle bermudagrass plots treated with four nitrogen rates with and without trinexapac-ethyl in field experiments (2003-04, Clemson, S.C.).

While everyone seems interested in ball roll on bentgrass greens, ball roll on bermudagrass greens has received no prior research.

Hybrid bermudagrass (Cynodon dactylon Pers. x C. transvaalensis Burtt-Davy) putting greens require intensive management practices to promote surface uniformity and ball roll consistency. Turfgrass professionals traditionally consider bermudagrass putting green surfaces inferior to finer-textured creeping bentgrass (Agrostis palustris Huds.) from inabilities of previous cultivars to withstand routine mowing heights lower than three-sixteenths of an inch (Beard, 1973).

Recently introduced dwarf-type bermudagrasses have lower growth habits with the capability of withstanding long-term mowing heights of one-eighth of an inch (McCarty and Miller, 2002). Compared to traditional bermudagrass putting green cultivars, dwarf-type bermudagrasses have finer leaf textures and higher per area shoot densities (Beard, 2002). These morphological characteristics provide bermudagrass putting green quality once exclusive to creeping bentgrass greens (McCarty and Miller, 2002).

Quick Tip

One of the greatest differences in routine management of bermudagrass and bentgrass putting greens are fertility requirements. Bermudagrass putting greens generally require two to three times as much annual nitrogen (N) inputs, ranging from 8 pounds to 24 pounds of N per 1,000 square feet, to meet growth requirements and compensate for nutrient loss through daily clipping removal (McCarty, 2005). Consequently, active shoot growth resulting from heavy fertilizations may disrupt surface uniformity and decrease putting green ball roll distances.

A practice commonly implemented to enhance putting green ball roll distances are the applications of plant growth regulators (PGRs). Suppressing leaf growth with PGRs may produce smoother putting surfaces by promoting lateral growth instead of undesirable top growth (Murphy et al., 2005). A gibberellic acid inhibitor, trinexapac-ethyl (TE), is safe for routine applications on dwarf-type bermudagrass putting greens to promote ball roll distances and surface uniformity (McCullough et al., 2005a). Turf managers also routinely apply TE to creeping bentgrass putting greens and other fine turfgrass areas.

Ball roll distances of dwarf bermudagrass putting green as influenced by N or TE have not been reported. However, research with TE on creeping bentgrass putting greens has been reported. Fagerness et al. (2000) evaluated monthly applications of TE on Penncross creeping bentgrass ball roll when maintained at one-eighth, five-thirty-seconds and three-sixteenths-of-an-inch mowing heights.

Long-term ball roll improvements were more consistent from reducing mowing height, while TE enhanced ball roll distances over the course of a given day. L-93 creeping bentgrass putting green ball roll distances have shown to be greater or equivalent to turf receiving supplemental and subsequent mowing operations following TE applications (McCullough et al., 2005b).

Turf managers may be able to reduce bentgrass putting green mowing frequencies without compromising ball roll distances following applications of TE.

Since bermudagrass putting greens may require a broad range of routine N fertilizations, evaluating the effects of N input with TE would advance the potential for practitioners to promote longer ball roll distances. A two-year field experiment investigated effects of routine N fertility and TE applications on TifEagle bermudagrass putting green ball roll distances.

Materials and methods Field experiments were conducted over 12 weeks from April to August in 2003 and 2004 on a TifEagle bermudagrass putting green at the Turf Service Center, Clemson (S.C.) University. The bermudagrass green was established in July 2002 and built approximately to USGA specifications (USGA Green Section Staff, 1993). The experimental design was a split block with four replications of 5-foot by 7-foot plots (Picture 1).