Landscape Contractor / Design Build Maintain

JUL 2018

LC/DBM provides landscape contractors with Educational, Imaginative and Practical information about their business, their employees, their machines and their projects.

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Summer Deficit Irrigation of Bermudagrass by Robert Green, Ph.D., Alan Moss, M.S., Emma Rae McDonough, B.S., Kelly Parkins, M.S., Ramesh Kumar, Ph.D., Eudell Vis, M.S., Valerie Mellano, Ph.D., Grant Klein, M.A. Top Over the course of two sum- mers, plots of bermudagrass were subjected to varying degrees of deficit irrigation to help determine the minimum amount of irrigation needed to maintain acceptable turfgrass qual- ity for the entire warm season, and the minimum amount of irrigation required if lower turfgrass quality is suitable. Above The amount of weekly irriga- tion for each plot was at a level of 100%, 75% or 50% calculated crop evapotranspiration under standard conditions (ET crop ). Additionally, adjustments were made for the lack of irrigation distribution uniformity (DU) for each plot, causing a small increase in the amounts. These photos taken on the same day show the turf quality at 50% optimal irrigation (top), 75% optimal irrigation (middle) and 100% optimal irrigation. T (Editor's note: The following article was excerpted from a research paper from a team led by Robert Green, Ph.D., the entirety of which can be found at https://tinyurl.com/yd2l2cxy .) Common bermudagrass and hybrid ber - mudagrass are very popular turfgrass spe- cies in warm climates across the United States. The growth characteristics, overall appearance and adaptation of bermuda- grass to these climates deliver a quality turf that will respond well to a range of maintenance levels. "Deficit irrigation," the practice of ir - rigating below optimal conditions helps conserve water, maintain water budgets, save on operating costs and more. Depend - ing on the degree of deficit, bermudagrass can continue to provide sufficient growth and recuperative ability, and acceptable turfgrass quality during the entire warm season. But what is the minimum amount of irrigation needed to maintain acceptable turfgrass quality for the entire warm sea - son, and what is the minimum amount of irrigation required if lower turfgrass quality is suitable? The Study The primary objective of this study was to begin to define irrigation requirements for a range of bermudagrass visual quality and color ratings during the warm season. Ratings were on a scale of 1 to 9 (where 1 = dead or brown; 5 = minimally accept - able; 6 = acceptable; and 9 = maximum quality or color). This study was conducted over two sum - mers on 12 well-established GN-1 hybrid bermudagrass plots located at the Center for Turf, Irrigation and Landscape Tech - nology at California State Polytechnic University, Pomona. Plots were located in full sun. Each plot was individually zoned and controlled. Prior to the study, plots were well irrigated to ensure uniform soil water content in the 0- to 12-inch root- zone depth. The amount of weekly irrigation for each plot was calculated based on several fac - tors including monthly warm-season turf- grass crop coefficient (K c ) developed in Ir- vine, Calif.; and a treatment level of either 100%, 75% or 50% calculated ET crop . Ad- ditionally, a scheduling multiplier was used to adjust for the lack of irrigation DU for 18 LC DBM Continued on page 20

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