Competitive Ability of Tall Fescue against Alfalfa as a Function of Summer Dormancy, Endophyte Infection, and Soil Moisture Availability

Abstract

ABSTRACTManagement practices of summer‐dormant cool‐season grasses, including compatible legume species, are not well understood. In a greenhouse experiment, competitive ability of two summer‐dormant (Flecha and TX06V) and a summer‐active (PDF) tall fescue [Schedonorus arundinaceus (Schreb.) Dumort = Lolium arundinaceum (Schreb.) Darbysh.] was evaluated in associations with alfalfa (Medicago sativa L.) cv. Bulldog 505. Fescue cultivars were either infected with Neotyphodium coenophialum (Morgan‐Jones & Gams.) Glenn, Bacon, & Hanlin comb. nov. fungal endophyte or noninfected. Monocultures and binary mixtures were exposed to a gradually imposed soil moisture deficit stress (30% soil water capacity [SWC]) from June through August or maintained at 90% SWC (control). Indices of competitive interactions (relative yield [RY], relative yield total [RYT], and aggressivity [AGR]) were calculated. The RY of summer‐dormant tall fescue was less, whereas RY of summer‐active tall fescue was similar to that of alfalfa. The RYT values for alfalfa–tall fescue mixtures were not different from 1 under nonlimited soil moisture, but alfalfa–Flecha mixture had RYT <1 under soil moisture deficit. The AGR of summer‐dormant tall fescue was lower, but AGR of summer‐active tall fescue was similar to that of alfalfa. Results suggest that summer‐active tall fescue effectively competes with alfalfa, but summer‐dormant tall fescue cultivars have lower competitive ability than alfalfa. In addition, endophyte infection increased competitive ability of TX06V and PDF but not of Flecha.