Date of Graduation

5-2022

Document Type

Thesis

Degree Name

Master of Science in Horticulture (MS)

Degree Level

Graduate

Department

Horticulture

Advisor

Michael D. Richardson

Committee Member

Douglas E. Karcher

Second Committee Member

Kristofor R. Brye

Third Committee Member

John C. Sorochan

Keywords

Warm-season putting greens, Transition zone, golf courses, Cold- and shade-tolerance

Abstract

The use of warm-season putting greens in the transition zone has increased in recent years. Ultradwarf bermudagrass (Cynodon dactylon (L.) Pers x C. transvaalensis Burtt-Davy) is the most prevalent warm-season putting green selection in the transition zone, however, newly developed greens-type zoysiagrass (Zoysia spp.) cultivars represent another potential selection for golf courses. The two major limitations of warm-season grasses in the transition zone are a general lack of cold- and shade-tolerance. Protective covers are essential to protect ultradwarf bermudagrass putting greens in the winter months. Unfortunately, golf courses can still experience winterkill underneath protective covers. Two field trials were conducted with a goal of improving upon management strategies to improve the performance and survival of golf course putting greens under stress. Both trials were conducted on sand-based rootzones and were managed with cultural practices consistent with golf course putting greens found in the region. The first trial was conducted during the winters of 2019-20 and 2020-21 on a putting green consisting of four replicated whole plots of the three most prevalent ultradwarf bermudagrass cultivars. The goal of the trial was to improve upon cover strategies by supplementing protective covers with three air gap materials to provide additional insulation. Although materials such as straw and batting fabric provided moderate soil temperature gains compared to the cover alone, protective covers alone provided sufficient protection from winterkill during adverse weather conditions. Because of the high purchasing cost and labor requirement associated, wall to wall coverage of air gaps is not likely feasible. Where air gaps could be valuable is spot coverage of portions of putting greens that are especially vulnerable to winterkill (shade, north slopes, high traffic) and historically receive winterkill. The second trial was conducted during the growing seasons (June to October) of 2020 and 2021 on a putting green consisting of three replicated whole plots of ‘Lazer’ zoysiagrass (Zoysia matrella (L.) Merrill x Z. minima (Colenso) Zotov). Shade is a significant problem for golf course putting greens, so it is important to identify the precise amount of light is needed to maintain an acceptable putting green. Zoysiagrass is generally more shade tolerant than bermudagrass, however, ‘Lazer’ zoysiagrass has not been studied. The goal of this trial was to compare ‘Lazer’ zoysiagrass to an industry-standard putting green selection, ‘TifEagle’ bermudagrass, under varying levels of shade and management practices. Management practices included two mowing heights (2.5- and 3.2-mm) and with or without the treatment of the plant growth regulator, trinexapac-ethyl. The minimum daily light integral (DLI) was determined for both species and surface characteristics, including ball roll distance and surface firmness, were monitored. ‘Lazer’ zoysiagrass demonstrated superior shade-tolerance and had a minimum DLI requirement about 10 mol m-2 d-1 less than ‘TifEagle’. Surface firmness was greater for ‘Lazer’, while ‘TifEagle’ produced greater ball roll distance for most rating dates. However, both species consistently produced industry-standard ball roll distance. Results from this trial suggest that ‘Lazer’ zoysia can produce acceptable putting green conditions and is better adapted than ‘TifEagle’ to moderate shade conditions.

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