The list keeps on growing. There are at least four turf species available for putting greens in the Southeast Region today: ultradwarf bermudagrass, creeping bentgrass, seashore paspalum, and zoysiagrass. Zoysiagrass? Yes. Diamond zoysiagrass is a variety released by Dr. Milt Engelke at Texas A&M University in 1996 and it has been planted on the putting greens at several golf courses in recent years.
Currently, the niche that Diamond appears best adapted to in the southeast region is on putting greens that receive too much shade for an ultradwarf bermudagrass to prosper and an inability to increase sunlight levels through removal of trees. Clemson University has embarked on numerous projects to better understand and identify best management practices for the Diamond zoysiagrass to produce desirable putting conditions.
The remainder of this article will evaluate research at Clemson University in the following areas:
- Shade tolerance
- Fertility inputs
- Plant Growth Regulator use
- Putting green performance
One of the advantages of converting to an ultradwarf bermudagrass putting green is its relative ease through no-till and quick establishment methods. A potential concern of using Diamond zoysiagrass as a putting green is its slow establishment rate. Currently, there is a lack of research to explore establishment techniques of Diamond zoysiagrass. However, previous research at Clemson demonstrated that Diamond can be established from sprigs in one growing season and meet putting green expectations within 12 weeks. The time required for establishment can be reduced with sprigging rates greater than 24 bushels per 1,000 square feet and total nitrogen input between 4-7 pounds N /per 1,000 square feet / year. Although slower than ultradwarf bermudagrass establishment, there are added benefits of Diamond as a putting green, which will be discussed further.
When making the switch from creeping bentgrass to ultradwarf bermudagrass, additional attention is necessary to evaluate potential shading problems associated with the surrounding landscape. Removal or aggressive pruning of trees is a standard practice to ensure that ultradwarf bermudagrass putting greens receive proper amounts of sunlight. Diamond exhibits superior shade tolerance over ultradwarf bermudagrasses, which translates into reduced tree work and preservation of the existing golf course. A recent study conducted at Clemson examined the shade tolerance of Diamond under varying levels of shade and trinexapac ethyl (Primo) applications. Diamond displayed acceptable turf quality under constant levels of 60 percent shade without weekly applications of Primo during the growing seasons of the two-year study, indicating its strong shade tolerance. However, turf quality improvements were found at 60 percent and 90 percent shade with weekly Primo applications at 1.5 oz/acre during the growing season.
Other recent research work conducted by Clemson examined Diamond putting green performance over two years under weekly applications of foliar applied nitrogen and Primo at the Cliffs turfgrass research facility in Marietta, S.C. Weekly readings of turf quality and ball roll distance were performed, as well as monthly thatch accumulation and surface firmness measurements using the USGA TruFirm™. These parameters provided the first look into the management practices necessary to meet golfer’s expectations and overall sustainability of Diamond putting greens in the transition zone.
Plant Growth Regulator Use
Results of this study found that management of fertility and Primo significantly influence the putting green performance of Diamond. Weekly applications of 0.20 pounds per 1,000 square feet of ammonium nitrate with Primo at 2 oz/acre provided acceptable turf quality and significantly increased ball speed and firmness. Although increased Nitrogen (N) rates led to higher turf quality ratings, their performance as a putting surface suffered as indicated by ball roll distance. A significant decrease in ball roll distance occurred as weekly N rate increased. This response also was exhibited for surface firmness when measured using the Trufirm. As weekly N level increased, surface firmness readings decreased. This is possibly due to a greater shoot density and increased vertical growth, leading to slower ball roll distances and increased TruFirm penetration. Soil moisture readings were not taken during this study and could significantly impact surface firmness of Diamond putting greens. Thatch depth increased throughout the growing season of both years.
However, there wasn’t correlation between total N input and thatch depth. A commonly recommended rate of 3 pounds N/per 1,000 square feet/year is a suitable fertility level for most zoysiagrasses in the Southeast, and findings of this study support this recommendation. Nitrogen inputs in excess of 3 pounds may lead to poor putting green performance; however, supplemental applications of quick release N sources should be conducted to promote growth and recovery. A decrease in mowing height, increase in PGR application rate or frequency, rolling, and cultivation could increase ball roll distanceon Diamond putting greens. A common mowing height of 0.125” was used in this study, but previous research at Clemson demonstrated that Diamond could be mowed as low as 0.098” without scalping or winter survival issues. In addition, thatch and mat control studies for Diamond zoysiagrass putting greens needs to be examined further. Throughout the two-year field study, no cultivation took place and significant increases in thatch depth were recorded.
Putting Green Performance
In summary, Diamond zoysiagrass has the potential to be installed and utilized successfully in the southeastern states as a putting green turfgrass alternative to bentgrass and ultradwarf bermudagrasses when shade issues exist and tree removal options are limited. Optimal fertility and pest control programs need to be investigated to maximize putting green performance without compromising turf quality and overall plant health. Additional research needs to be conducted to examine cultivation, lowered mowing heights, increased PGR rate/application intervals and surface rolling to further enhance putting green performance. Although the future looks bright for Diamond, many questions need to be answered. Diamond does, however, seem to have a niche at certain locations in the Southeast Region where shade is an issue and current putting green turfgrasses won’t work.
Nick Menchyk and Frank Bethea Jr. are graduate research assistants and Dr. Haibo Liu is a professor of turfgrass science and management at Clemson University. All three scientists are avid golfers and enjoy playing golf on any type of putting green turf.
We would like to thank the following people for their support of this article: The Cliffs Communities, John Brown of New Life Turf, Dr. Clint Waltz of University of Georgia, Jeff Atkinson and Brandon Stiglbauer.
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