Figure 1. Locations and researchers working together to document actual annual water use by turfgrasses. Lead investigator was John Stier, PhD, at the University of Tennessee. Doug Karcher, PhD, at the University of Arkansas served as the statistician on the project. All other investigators are professors at land grant universities. The background map is sourced from Milesi et al. (2005) with the darkened areas indicating the amount of turf area.
= bermudagrass, zoysiagrass, St. Augustinegrass, and buffalograss; TN = bermudagrass, zoysiagrass, Kentucky bluegrass, and tall fescue; MN = Kentucky bluegrass and a fine fescue mix with 20 percent Kentucky bluegrass; CT = Kentucky bluegrass, fine fescue, a fine fescue/Kentucky bluegrass mix, and a tall fescue mixed with 10 percent Kentucky bluegrass. Varieties were chosen by the producer supplying the sod. Management was conducted using Extension recommendations for that state.
Plots were sodded in 2015 and testing was conducted throughout the 2016 and 2017 growing seasons. At most sites, individual plots were split so each sod type received both a high and a low amount of nitrogen fertilizer based on Extension information. Plots were monitored at least once weekly, more often during mid-summer, for green color. Te amount of water needed to maintain at least 50 percent green color was measured with flow meters attached to hand-held hoses as water was applied.
California had the greatest irrigation requirements of any site, from 13 to 26 inches annually, depending on species and the year. Utah’s grasses required 5 to 10 inches of
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water annually. Connecticut grasses never required any irrigation, and Minnesota required less than 1 inch of water in 2017. Results varied between the years at each site, for example, Dallas, TX, required 0 to 8/10 of an inch in 2016 and 1 to 3 inches in 2017, while Knoxville, TN, grasses required 3 to 13 inches in 2016 and 3 to 4-1/2 inches in 2017. July and August months tended to require the greatest amount of irrigation for all grasses in both years. Estimated evapotranspiration (ET, water loss through evaporation and transpiration from the turf and soil combined) did not seem to be a good predictor of irrigation needs. In California, the amount of irrigation required to maintain 50 percent green cover ranged from about 50 to 100 percent of ET depending on the year and species. At other locations, the amount of irrigation required ranged from 0 to about 60 percent of ET in any given month of the growing season.
Te final report for this project is currently being prepared for journal submission by Dr. John Stier and his team. Once this research has been published, we will be able to report on this project further, so stay tuned!
TPI Turf News September/October 2019
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