locations, researchers replace either 40, 60 or 80 percent of ETo (as determined by local weather station data) for cool- season grasses, or 30, 45, or 60 percent ETo for warm- season grasses. Tis scenario is more typical of irrigation patterns in the western U.S. with 25 inches or less of annual rainfall. Approach 2 data indicates the reduced irrigation level each entry will survive, and at what level each entry will deliver acceptable turf quality. Terefore, the two approaches address the needs
across the U.S., from the humid, eastern U.S. with 30+ inches of annual rainfall but with occasional prolonged drought periods, to the arid western U.S. where annual summer drought periods are expected. Te warm-season version of this trial was
established at ten locations in summer 2018. Te cool- season version of this trial was established in fall 2016 or spring 2017 at ten total sites, five under rain exclusion shelters in the eastern U.S. (Approach 1) and five in western U.S. field sites (Approach 2). Te cool-season version includes fifteen Kentucky bluegrasses, nineteen tall fescues and one perennial ryegrass (as a control entry). Te first data from the cool-season trial was
collected in 2017 at six of the ten locations. Four Approach 1 (shelter) locations collected data during a 100-day induced drought period, and in some cases, large differences were noted in the amount of water used by entries, however very little statistical differences were noted among entries. For 2018, we changed the re- watering procedure threshold to 65 percent green cover, as well as expanded our statistical analysis for all sites to include separate Kentucky bluegrass and tall fescue tables. Tese changes resulted in virtually no statistical
differences at Griffin, GA, Amherst, MA, and Fayetteville, AR, even though in some instances large differences in the amount of water used were evident (range = 4.3 to 72 mm; 1 inch = 25.4 mm). At College Park, MD, statistical differences were noted, mainly among the Kentucky bluegrass entries, with BAR PP 110358, PST-KS-13-141, Blue Devil, NAI-13-14 and NAI-13-132 the top entries. BAR PP 110258 used less water than many of the tall fescue entries (169.3 mm). Tall fescues using the least water at College Park, MD, (156.7 - 169.3 mm) include RS4, Catalyst, Monet, LTP-SYN-A3 and Titanium LS. Te greatest entry separation in any Approach 1
(shelter) site was recorded at West Lafayette, IN. Like most sites, the tall fescues, in general, needed less water to remain green than most bluegrasses. However, at West Lafayette there was a great range of performance, from 161 - 317.7 mm of water used for tall fescue entries to 216 - 313.7 mm for Kentucky bluegrass. Tall fescues with the least water required at this site in 2018 include DLFPS-321/3678 (161 mm), DLFPS-321/3677 (173.7 mm) and RS4 (175.7 mm). For bluegrass at West Lafayette, Barrari (216 mm), NAI-13-132 (216.3 mm) and NAI-13-14 (228.7 mm) used the least water in 2018. In 2017, only Approach 2 sites at Riverside, CA,
TPI Turf News July/August 2019
and Las Cruces, NM, collected data. In 2018, all five sites collected data, with four locations (Riverside, Las Cruces, Fort Collins, CO, and Logan, UT) irrigating at 40, 60 and 80 percent ETo replacement, and St. Paul, MN, using 0, 25 and 75 percent ETo replacement, while adjusting for any rainfall received during the 120 day drought period. At Riverside, the 40 percent ETo irrigation regime
was very harsh on all entries, with no entry delivering even acceptable lawn turf quality ratings (6.0+) throughout the drought period, or even minimally acceptable turf quality ratings (5.0) 60 days into the drought period. Turf quality ratings averaged over the entire season at 40 percent ETo replacement showed all entries with 5.0 score or lower. Te 60 percent ETo replacement regime did not show a single entry with an acceptable mean turf quality rating (6.0) at end of the season, including recovery time. Te 60 percent ETo regime did show some statistical significance among some Kentucky bluegrass entries, but not tall fescue. Te 80 percent ETo regime, which is considered adequate replacement of ET for cool-season grasses, did some show entries with acceptable turf quality averages, but with no statistical difference among Kentucky bluegrass or tall fescue entries. Te Las Cruces, NM, site, while being hot during
summer, is not quite as harsh as Riverside (maybe due to some summer rains), which elevated some quality ratings to acceptable levels. Statistical significance was only noted between the top bluegrass entry (PST-K11-118) and the lowest entry (Midnight) at 40 percent ETo. No statistical significance was seen at the 60 percent level, while several entries performed statistically better at the least harsh, 80 percent ETo replacement level. Statistical significance among tall fescue was not seen at the 40 percent and 60 percent ETo levels but was noted at the 80 percent level. At the 80 percent ETo level, the top performing Kentucky bluegrasses were NAI-13-14, NAI-13-132, Blue Devil and Midnight; the top tall fescues were Tor, MRSL TF15, DLFPS-321/3678, RS4, Tunderstruck and Titanium LS.
Te Warm-Season Water Use trial at Starkville, MS, at the start of drought treatments. Photo courtesy of Dr. Barry Stewart, Mississippi State University
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