Jointed Goatgrass Competitiveness is Influenced by Winter Wheat Seeding Rate

Abstract. Jointed goatgrass is a troublesome weed in winter wheat. Winter wheat seeding rates are easily adjusted by growers and have been shown to reduce competition from some weeds. Field experiments were initiated in the fall of 1994 and complete during 1996 at Hays, KS; Sidney, NE; and Torrington (1994 to 1995) and Archer (1995 to 1996), WY to determine the effect of wheat seeding rates (ranging from 33 to 101 kg/ha) on jointed goatgrass competitiveness. Jointed goatgrass densities averaged 25 plants/m² at Kansas and Wyoming, while Nebraska densities averaged 30 plants/m². Winter wheat plant densities, 42 days after planting, increased as the whet seeding rate increased. The presence of jointed goatgrass did not affect winter wheat plant densities. Jointed goatgrass reproductive tiller density at harvest, spikelet production, and biomass were all decreased as wheat seeding rates were increased at the Wyoming locations. Wheat seeding rate did not affect jointed goatgrass reproductive success at Nebraska or Kansas. The ability of jointed goatgrass to reduce winter wheat reproductive tiller density at harvest decreased as wheat seeding rates were increased at Nebraska and Wyoming. Winter wheat grain yield increased as wheat seeding rate increased at Wyoming and at Nebraska during 1996, but otherwise grain yield was not affected by wheat seeding rate. Jointed goatgrass reduced wheat grain yield at all locations, but the extent of the loss was not influenced by wheat seeding rate. Wheat grain yield was least affected by jointed goatgrass interference at Wyoming.

Selecting higher wheat seeding rates never reduced winter wheat grain yields, but did show promise for reducing jointed goatgrass reproductive success. Wheat seeding rates can play a role in integrated jointed goatgrass management systems.