MULTIYEAR USE OF KILLED STRIPS FOR FORAGE AND GRAIN-SORGHUM PRODUCTION IN A TALL FESCUE PASTURE

Tall fescue (Festuca arundinacea Schreb.) is an excellent perennial gr ass for spring and fall forage production and for erosion control on s loping land. Tall fescue forage production is poor during the summer, however. Our objective was to improve pasture productivity without inc reasing erodibility by planting a sorghum x sudan hybrid [Sorghum bico lor (L.) Moench x Sorghum bicolor L. Moench] (S x S) or grain sorghum [Sorghum bicolor (L.) Moench] (GS) in 12 in. killed strips of tall fes cue and to determine if strips could be used in subsequent pars withou t additional herbicide treatment. Forage from a block of tall fescue w as harvested in May 1990, and plants were allowed to regrow for 1 wk b efore application of glyphosate in 12 in. strips on 30 in. centers at two rates of 1.2 and 0.6 lb ai/acre (strip-kill). For control treatmen ts, the entire tall fescue sod was killed (complete-kill) or tall fesc ue was not sprayed in order to measure forage production from the gras s monoculture. The SxS (cv. FFR 201) was planted into strip-kill and c omplete-kill plots 1 wk after glyphosate treatment in 1990 and again i n 1991 and 1992 without additional glyphosate treatment. In May 1991, GS (cv. MFA GS-10) was planted into strip-kill and complete-kill plots and these! strips were used again in 1992. Tall fescue was successful ly killed with a single application of each rate of glyphosate in the strip-kill and complete-kill systems. There was little difference in S xS dry matter yield or GS grain yield between glyphosate treatments, D ry matter yield of S x S in strip-kill plots decreased each year after initial treatment in 1990, probably a result of increased competition from tall fescue encroachment into the killed strips. Dry matter yiel d of S x S in strip-kill plots was 16, 49, and 52% less than that of t he complete-kid plots in 1990, 1991, and 1992, respectively. Tall fesc ue yield in strip-kill plots was only slightly less than that of tall fescue (monoculture) control plots, Total forage yield (S x S plus tal l fescue) in the strip-kill plots was 3.49, 2.39, and 1.63 tons/acre g reater than that of the tall fescue (monoculture) control in 1990, 199 1, and 1992, respectively, Grain sorghum yield in strip-kill plots was 25 bu/acre less than that in complete-kill plots in 1991 and 53 bu/ac re less than that in complete-kill plots in 1991, Planting S x S into the same strip-kill plots is feasible for 3 yr, however for GS to be s uccessful in a strip-kill system, tall fescue strips must be killed an nually.