Golf Course Management

JUN 2019

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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06.19 GOLF COURSE MANAGEMENT 67 covery usually occurs only after periods of sufficient rainfall. Bermuda- grass [Cynodon dactylon (L.) Pers.] is one of the most widely used warm- season turfgrasses in arid and semiarid climate zones because it requires significantly less water than cool-season grasses, tolerates traffic, and can be maintained at all mowing heights needed for turf areas (1). Chemical aids Soil surfactants and plant growth regulators are two products that have been used to maintain turf quality under reduced irrigation or drought conditions. Soil surfactants, also called wetting agents, are chemicals that decrease the interfacial tension between hydrophobic and hydrophilic surfaces of soil particles (2). Soil surfactants are commonly used to pre - vent and treat localized dry spots and areas of water repellency in the soil. Although the effects of surfactants on water repellency and localized dry spots have been widely studied, their use in large-scale efforts to help conserve irrigation water has been investigated only recently (4). Soil sur- factants increase water uniformity and water availability in the root zone, resulting in better turfgrass quality under drought conditions. Plant growth regulators are another class of compounds that have been shown to reduce water use in plants. Since its introduction in 1990, the use of the plant growth regulator trinexapac-ethyl (Primo Maxx, Syngenta) has become standard practice, particularly on golf courses, to maintain high-quality turfgrass. Primo Maxx is used primarily to reduce plant growth and thereby reduce mowing frequency, as well as to increase turfgrass density, color and resistance to stress. More recently, researchers have reported that bermudagrass maintained under drought conditions and treated with trinexapac-ethyl, had higher turfgrass quality than un- treated controls (5). Both soil surfactants and plant growth regulators have shown the potential to lower irrigation requirements and increase turfgrass quality under drought conditions. We hypothesized that combining a surfac- tant with a plant growth regulator would more effectively increase turf- grass quality and lower water requirements than using each chemical on its own. Materials and methods A three-year study was conducted from 2014 to 2016 on mature Prin- cess 77 bermudagrass (Cynodon dactylon L.) maintained at a fairway height of 0.5 inch (1.27 centimeters). Œe research area was located adja- cent to New Mexico State University's golf course in Las Cruces, N.M. (arid, elevation of 4,150 feet [1,265 meters]). Irrigation water was provided from an overhead sprinkler system. Œe treatments were: • Nontreated control • Œe surfactant Revolution (Aquatrols) at 6 ounces/1,000 square feet (20 liters/hectare) • Œe plant growth regulator Primo Maxx (a.i. trinexapac-ethyl) at 0.25 ounce/1,000 square feet (1.6 liters/hectare) • Revolution + Primo Maxx (tank-mixed) Revolution and Primo Maxx were applied at 28-day intervals from May until October, and irrigation was withheld from the plots for two hours following application to allow Primo Maxx to enter the plant sys- tem. Irrigation levels were 50% ETos (severe drought), 65% ETos (moder- ate drought) and 80% ETos (unstressed control treatment). Results and discussion Cover Plots receiving a combination of the surfactant and trinexapac-ethyl 100 90 80 70 60 100 90 80 70 60 100 90 80 70 60 Control TE Surfactant Surfactant + TE 2014 2015 2016 50% 65% 85% % Green cover % Green cover % Green cover ETos LSD=4 LSD=7 LSD=4 Figure 1. Percent green cover of Princess 77 bermudagrass treated with either trinexapac-ethyl (TE), Revolution (Surfactant), or a combination of both products and irrigated at either 50%, 65% or 85% ETos in 2014, 2015 and 2016. Values represent an average of 30 data points and are pooled across six sampling months (June to November) and five replicates. Percent green cover

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