Landscape Architect & Specifier News

JUL 2018

LASN is a photographically oriented, professional journal featuring topics of concern and state-of-the-art projects designed or influenced by registered Landscape Architects.

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74 Landscape Architect and Specifier News The amount of weekly irrigation for each plot was calculated based on several factors including monthly warm-season turfgrass crop coeffcient (K c ) developed in Irvine, Calif.; and a treatment level of either 100%, 75% or 50% calculated ET crop . Additionally, a scheduling multiplier was used to adjust for the lack of irrigation distribution uniformity (DU) for each plot; this caused a small increase in the amount of applied irrigation. Plots were mowed two days per week with a walk-behind reel mower. Height of cut was 0.75 inch (1.9 cm) during the first summer, and 0.87 inch (2.2 cm) during the second one. Plots were fertilized by hand once every two weeks at a nitrogen rate of 0.30 pound/1,000 square feet with a 16N-6P 2 O 5 -8K 2 O granular fertilizer. Visual turfgrass quality and color ratings were taken once every two weeks (nine days after fertilization and two days after mowing). Results and Conclusions During both years, overall average visual turfgrass quality and color were greater than 6.0 (acceptable) for the Left: During both years the study was conducted, overall average visual turfgrass quality and color were greater than 6.0 (acceptable) for the 100% and 75% optimal treatments. Even the 50% optimal treatment was almost always higher than the minimally acceptable rating of 5.0 for both ratings. Below: The amount of weekly irrigation for each plot was at a level of either 100%, 75% or 50% calculated crop evapotranspiration under standard conditions (ET crop ). Additionally, a scheduling multiplier was used to adjust for the lack of irrigation distribution uniformity (DU) for each plot; this caused a small increase in the amount of applied irrigation. These photos taken on the same day show the turf quality at 50% optimal irrigation, 75% optimal irrigation, and 100% optimal irrigation. 100% and 75% optimal treatments; the 50% optimal treatment average was not lower than 5.7, which is considerably higher than the minimally acceptable rating of 5.0. In the study, total salts did not build up appreciably in the 0- to 12- inch soil profile because they were irrigated with a high-quality recycled water. In other situations, salt buildup could be a problem. Fortunately, bermudagrass has been reported to possess the highest salt-tolerance rating. Results show that 75% to 50% optimal (63% to 41% ET o , respectively, for the duration of the warm season) can be used while maintaining acceptable to minimally acceptable bermudagrass quality and color. But the 50% optimal treatment could be too low for many situations, such as desert areas. Results from deficit irrigation will vary because of multiple factors, such as soil texture and organic matter, climate, antecedent soil water content, grass maturity, cultural conditions, DU, and irrigation water quality. 50% 75% 100% Year 1 Year 1 Year 2 Year 2 i r r i g a t i o n

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