Date of Graduation

5-2018

Document Type

Thesis

Degree Name

Master of Science in Horticulture (MS)

Degree Level

Graduate

Department

Horticulture

Advisor/Mentor

Karcher, Douglas E.

Committee Member

Richardson, Michael D.

Second Committee Member

McDonald, Garry V.

Third Committee Member

Purcell, Larry C.

Keywords

Creeping Bentgrass; Daily Light Integral; Light Requirement; Photosynthetically Active Radiation; Shade Tolerance; Turfgrass

Abstract

Light is one of the primary growth-limiting factors of turfgrass. Without sufficient quantities of photosynthetically active radiation (PAR; 400-700 nm wavelength), turfgrass quality will decline and could ultimately result in plant death. PAR light can be expressed in a daily quantity known as the daily light integral (DLI) and has been utilized to determine minimum light requirements for turfgrass as well as other plants. With an estimated 25% of all turfgrass being maintained under some level of shaded conditions, it is imperative to define minimum DLI requirements of various turfgrass systems to ensure acceptable turf quality. In addition, it is necessary to evaluate novel methods of quantifying and assessing light conditions so that turfgrass managers can direct appropriate agronomic decisions. This research aims to determine a minimum DLI requirement of a creeping bentgrass putting green, evaluate an efficient quantification method of DLI requirements for multiple warm season turfgrasses in an established landscape, and to estimate PAR reduction with total visible light measuring devices under various tree species. After evaluation of creeping bentgrass putting green turfgrass quality and coverage under 0, 70, 80, and 90% shade for two years, a minimum DLI requirement was estimated to be 30 mol m-2 d-1. In a controlled research setting over two years, minimum DLI requirements of four warm season turf types, ‘Astro-DLM’ bermudagrass, common bermudagrass, ‘Cavalier’ zoysiagrass, and ‘Meyer’ zoysiagrass, were determined to be 20.4, 25.9, 15.0, and 21.1 mol m-2 d-1, respectively. However, an efficient method to determine DLI requirements in an established golf course landscape was able to accurately estimate DLI requirements for just two of the four warm season turf types and further evaluation is needed. PAR reduction beneath tree shade canopies varied among tree species, but was not able to be estimated from visible light measurements with sufficient precision. This results of this research establishes minimum DLI requirements of popular turfgrass selections for turfgrass managers to utilize as a baseline when making agronomic decisions in shaded conditions. Additionally, alternate methodology is evaluated to efficiently and accurately estimate minimum DLI requirements.

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