Kochia (Bassia Scoparia) Growth and Fecundity As Influenced By Crop Competition and Weed Density

Kochia [Bassia scoparia (L.) A. J. Scott] represents one the most troublesome weeds in crop production systems in the North American Great Plains. The development of herbicide-resistant B. scoparia populations further exacerbated this problem. More ecologically driven approaches to its control are necessary. This study examined the competitive effects of four crops (sugar beet, soybean, barley, and corn) in combination with B. scoparia densities (3, 13, 24, 47, 94, and 188 plants m-2) on B. scoparia development and seed production across 2 years. Corn and barley had the greatest impact on B. scoparia growth and fecundity. B. scoparia biomass was 87 and 82% lower and seed production was 98 and 96% lower (pB. scoparia biomass and seed production. Barley had greatest effect in delaying B. scoparia flowering which occurred 113 days after B. scoparia emergence (pB. scoparia biomass by 70 and 65% and seed production by 84 and 80% (pB. scoparia densities resulted in reductions in B. scoparia width, number of primary branches, biomass plant-1, and seeds plant-1 but increased B. scoparia height, biomass m-2, and seeds m-2 (pB. scoparia through reduced fecundity and delayed flowering, with the latter providing a window of opportunity for post-harvest control. The effects observed here were isolated from differences in herbicide practices that are associated with each of these crops, differences that have a dramatic effect on B. scoparia in their own right.