Timing and Frequency of Between‐Row Mowing and Band‐Applied Herbicide for Annual Weed Control in Soybean

Abstract

Alternative ways are needed to control weeds in field crops that reduce or prevent both herbicide contamination of surface and ground water and soil erosion. A new weed management system, which consisted of band‐applied herbicides over the soybean [Glycine max (L.) Merr., ‘Morsoy 9137’] row and two or more between‐row (BR) mowings, was optimized in a soybean field near Columbia, MO. Between‐row mowing very close to the soil surface twice with a mower killed or suppressed annual grass and broadleaf weeds, chiefly giant foxtail (Setaria faberi R. Herrm.), common ragweed (Ambrosia artemisiifolia L.), and waterhemp species (Amaranthus spp.), when properly timed. When band‐applied herbicide controlled weeds within the crop row, annual weeds between rows could be mowed once when the tallest weeds were 8 to 24 cm tall and again just before crop canopy closure, without yield loss. No more than two BR mowings were needed to control annual weeds. Shading by crop canopy closure contributed to weed suppression in this BR‐mowing weed management system. Soybean yield in the BR‐mowing weed management system could not be statistically distinguished from hoed, weed‐free check plots or broadcast‐herbicide treatments and was greater than the weedy check plots. Herbicide use was reduced 50% by banding because only 50% of the field area was sprayed. The BR‐mowing weed management system may have use in environmentally sensitive areas to help reduce soil erosion and/or water contamination by herbicides.