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 grass for spring and fall forage production and for erosion control on sloping land. Tall fescue forage production is poor during the summer, however. Our objective was to improve pasture productivity without increasing erodibility by planting a sorghum x sudan hybrid [Sorghum bicolor (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 fescue and to determine if strips could be used in subsequent pars without additional herbicide treatment. Forage from a block of tall fescue was harvested in May 1990, and plants were allowed to regrow for 1 wk before 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 treatments, the entire tall fescue sod was killed (complete-kill) or tall fescue was not sprayed in order to measure forage production from the grass monoculture. The SxS (cv. FFR 201) was planted into strip-kill and complete-kill plots 1 wk after glyphosate treatment in 1990 and again in 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 successfully killed with a single application of each rate of glyphosate in the strip-kill and complete-kill systems. There was little difference in SxS dry matter yield or GS grain yield between glyphosate treatments, Dry 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 yield of S x S in strip-kill plots was 16, 49, and 52% less than that of the complete-kid plots in 1990, 1991, and 1992, respectively. Tall fescue yield in strip-kill plots was only slightly less than that of tall fescue (monoculture) control plots, Total forage yield (S x S plus tall fescue) in the strip-kill plots was 3.49, 2.39, and 1.63 tons/acre greater than that of the tall fescue (monoculture) control in 1990, 1991, 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/acre 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 successful in a strip-kill system, tall fescue strips must be killed annually.