Date of Award

5-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Plant and Environmental Science

Committee Member

Dr. L.B. McCarty, Committee Chair

Committee Member

Dr. S.B. Martin

Committee Member

Dr. Christina Wells

Abstract

With the ever changing market of the golf course industry, turfgrass managers are constantly exploring options of promoting healthier turf while also maintaining an appropriate budget. One constant problem is how to manage and relieve summer stress on bentgrass [Agrostis stolonifera L. var palustris (Huds.)] putting greens. Application of pigmented products is an increasingly popular management practice attempting to relieve some of this stress associated with high temperatures and light intensity. Several of these products are also marketed for use on warm-season grasses such as hybrid bermudagrass as a mean of providing winter green color and improving or hastening breaking of winter dormancy. Research on use of these products on creeping bentgrass has increased in recent years but is still limited, while research on warm-season grasses is sparse. The objective of this study was therefore to investigate the impacts of pigment-containing products on turfgrass physiology of warm- and cool-season grasses during periods of respective stress. Three pigment-containing products and three pigment-free products were selected for testing alone and in combinations for two field studies in 2013 and 2014 on creeping bentgrass and hybrid bermudagrass: Turf Screen (zinc oxide and titanium dioxide), PAR (copper-based pigment), Chipco Signature (fosetyl-aluminum and a copper-based pigment), Title Phyte (potassium phosphite), Turf Screen + Title Phyte, PAR + Title Phyte, and Fosetyl-Al (fosetyl-aluminum). Products were applied bi-weekly for twelve weeks. Civitas (mineral oil) + Harmonizer (copper based pigment) and Harmonizer alone were added for 2014 field study on hybrid bermudagrass. All products were used in two separate growth chamber studies investigating health of bentgrass in high temperatures and bermudagrass in freezing temperatures. All products were also used in a bermudagrass dormancy breaking study. In field studies, application of products caused a general increase in canopy temperatures (~0.5 to 3°C) compared to untreated controls of both grass species. Bentgrass treated with pigmented products exhibited greater (~6 to 20 µmol CO2 cm-2 s-1) carbon dioxide exchange rates (CER) than that of the untreated control indicating a reduction in photosynthesis. Applications of Chipco Signature to hybrid bermudagrass in year two resulted in a more negative CER (-28.295 µmol CO2 cm-2 s-1) indicating greater photosynthetic activity. Decreased (24-50 relative chlorophyll) chlorophyll concentration in creeping bentgrass was observed in both study years by all treatments compared to the untreated while no effect was observed in bermudagrass. No effect on root mass following product use was observed in either grass species. Tissue and soil analysis of creeping bentgrass indicated that Turf Screen and Turf Screen + Title Phyte applications increased zinc concentration in both the plant and soil by an average of 820 ppm and 4.75 kg ha-1, respectively. Applications of PAR, PAR + Title Phyte, and Turf Screen + Title Phyte caused an increase of ~27 ppm of copper in plant tissue of bentgrass. Applications to bermudagrass had similar results with zinc in soil and tissue analysis. Growth chamber studies on creeping bentgrass further confirmed field studies. Application of treatments in study one resulted in statistically greater CER than unstressed control by an average of ~15.4 µmol CO2 cm-2 s-1. Fluorescence ratings in study two yielded greater (~13) Fv/Fm values in the unstressed control than any other treatment indicating reduced photosynthetic efficiency. Growth chamber studies on hybrid bermudagrass focusing on freezing stress indicated a net increase (~8 to 21 µmol CO2 cm-2 s-1) in CER of Title Phyte, stressed control, and Turf Screen in both studies over the unstressed control. However, overall fluorescence of all treatments was reduced compared to the unstressed control by a Fv/Fm value of ~12. Spring green-up study revealed no differences among treatments on earlier breaking of dormancy of hybrid bermudagrass. The increased bentgrass CER of treated turf indicates a reduction in net photosynthesis while increased canopy temperatures promote a more stressful environment. Results suggest that several products investigated may promote greater heat stress on creeping bentgrass during times of hot, humid weather. Applications to bermudagrass during the same time period did not show negative effects, however the concentration of heavy metals could create future toxicity problems.

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