Effect of Weeds on Soybean Yield and Harvesting Efficiency

A reduction in soybean (Glycine max (L.) Merr.) yield of 25% (1968) to 30% (1969) resulted from one smooth pigweed (Amaranthus hybridus L.) per ft in 30-inch rows. A giant foxtail (Setaria faberii Herrm.) infestation of one plant per ft in 30-inch rows reduced yield 13% in 1969. Harvesting before weeds were desiccated resulted in significant threshing and separating losses as speed was increased from 1 to 2 and 3 mph. Stubble, lodging, and stalk losses were more than double in the pigweed and foxtail plots when compared to the weed-free plots after weeds were desiccated by frost.