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The Effect of Winter Wheat Seeding Rate on Jointed Goatgrass (Aegilops cylindrica Host) Competitiveness

B.F. Kappler, D.J. Lyon, P.W. Stahlman, and S.D. Miller
1996 NCWSS Proceedings, Vol. 51

Abstract. Jointed goatgrass (Aegilops cylindrica Host) is a troublesome weed in winter wheat. Winter wheat seeding rates are easily adjusted by growers and wheat seeding rates have been shown to influence competition by some weeds. Field experiments were initiated in the fall of 1994 and completed in 1996 at Kansas, Nebraska, and Wyoming to determine the effect of wheat seeding rates (ranging from 33 to 101 kg/ha) jointed goatgrass competitiveness.

Winter wheat plant densities 42 days after planting typically increased as the wheat seeding rate increased. The presence of jointed goatgrass did not effect winter wheat plant densities. The effect of wheat seeding rate varied by geographic location. Jointed goatgrass reproductive tiller density at harvest, spikelet production, and biomass were all decreased as seeding rates were increased at the Wyoming location. Wheat seeding rate did not affect jointed goatgrass to reduce winter wheat reproductive tiller density at harvest decreased as wheat seeding rates were increased at Nebraska and Wyoming. The presence or absence of jointed goatgrass also influenced wheat reproductive tiller density. Grain yield of winter wheat was only affected by wheat seeding rate at Wyoming and during 1995 at Nebraska. Winter wheat grain yield either increased or remained the same as wheat seeding rate increased, except when Ike was grown at Kansas in 1995. Jointed goatgrass reduced wheat grain yield at all locations. However, wheat seeding rate and jointed goatgrass did not interact to have an effect on wheat grain yield. Wheat grain yield was least affected by jointed goatgrass interference at Wyoming. Selecting higher wheat seeding rates rarely reduced winter wheat grain yields, but did show promise for reducing jointed goatgrass reproductive success. The cost of wheat seed for potential control is probably less than the cost of controlling jointed goatgrass later. Wheat seeding rates can have a role in integrated jointed goatgrass management systems.