fescue/Kentucky bluegrass mixture, and Bullseye tall fescue. However, quality scores across locations were generally low as expected, with no entries at the Raleigh, NC, Lincoln, NE, and Kennett Square, PA, locations finishing with a turf quality average score of at least 5.0, the NTEP threshold for minimum acceptable quality under low maintenance. Terefore, we theorize that the performance of these entries will change a lot, and may continue to decline over the remaining three years of this trial.
Cool-Season Water Use With the need to reduce turfgrass water use,
USGA is partnering with NTEP to evaluate both cool- and warm-season grasses for water efficiency and performance under lower water use. Te USGA has paid to install rain exclusion shelters at ten sites, five in the northern or transition zones (to evaluate cool-season grasses) and five shelters in the southern U.S. to evaluate warm-season grass water use and drought tolerance. Within these shelters, cooperators restrict irrigation for a period of 100 days for cool-season grasses, or 120-150 days for warm-season grasses. Tese ‘drought seasons’ under the shelters are part of Approach 1, which is a measurement of the amount of water needed to maintain a prescribed level of green during that period. Ten trial locations in the drier western U.S.
states (five each for cool-season and warm-season grasses) manage under Approach 2, which utilizes three evapotranspiration replacement rates (ETo
for ). In Approach 2
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
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 will deliver acceptable turf quality.
Terefore, the two approaches
address the needs across the U.S., from the humid, eastern U.S. with 30 plus 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 is being 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
TPI Turf News July/August 2018 49
version includes fifteen Kentucky bluegrasses, nineteen tall fescues and one perennial ryegrass. 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 amount of water used by entries. In some locations, the difference between the least water using entries and the most water using entries was two-fold (for instance, 46.7 mm of water to 97.7 mm of water), but very few statistically significant differences were noted, either within Kentucky bluegrass or tall fescue entries. Griffin, GA, was the only Approach 1 site where significant differences were noted in water used, but only with tall fescue. PST-R511 and RS4 tall fescue used the least water at Griffin, along with nine other entries that were statistically similar. Te range of tall fescue water use at Griffin was 76.3 – 211.7 mm (LSD=76.3) in 2017. Hopefully, in 2018 we can obtain great statistical significance among Approach 1 entries. Only Approach 2 sites at Riverside, CA, and Las
Cruces, NM, collected data in 2017. Both locations ran irrigation at 40, 60 and 80 percent ETo
replacement,
while adjusting for any rainfall received during the 120 day drought period. Very little rainfall was noted at the Riverside, CA, location during the ‘drought season’ while Las Cruces experienced some precipitation from summer storms. Consequently, summer stress was more pronounced at Riverside than Las Cruces. At Riverside, the 40 percent ETo
irrigation
regime was very harsh on all entries, with only Babe Kentucky bluegrass delivering acceptable turf quality ratings (>6.0) 45 days into the drought period. Not unexpectedly, no entry showed acceptable turf quality throughout the entire 40 percent ETo
replacement season
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