California researchers found dramatic differences in yield and persistence among grasses subjected to varying irrigation treatments.

Next to alfalfa, irrigated grass pasture is the highest water-use crop in the state’s intermountain region, point out Steve Orloff, Siskiyou County farm advisor, and Dan Putnam, University of California alfalfa and forage Extension specialist. Irrigation water is a limited resource, and producers worry about its long-term availability. So the two Extension specialists did a study to determine the effect of deficit irrigation on pasture grasses.

Twenty six grasses were evaluated, including 10 tall fescue varieties, seven orchardgrass varieties, four bromegrass species, three wheatgrass species and a single variety each of festulolium and harding grass. Three irrigation treatments were imposed: normal full-season irrigation, irrigation cutoff on June 1, and irrigation cutoff on July 15.

Unlike previous results for alfalfa, grass yield dropped dramatically in the cutting following water removal. Bromegrass and wheatgrass were more drought tolerant than tall fescue or orchardgrass, but they didn’t tolerate full-season irrigation, and when fully irrigated their stands were dramatically reduced. Orchardgrass tolerated a single season of deficit irrigation but over several years it didn’t persist as well as tall fescue.

“Overall, tall fescue appeared to be the species best adapted to the combination of full irrigation and deficit irrigation,” Orloff and Putnam report.