Nutsedge is not very competitive with soybeans. Cultivation alone often reduces competition enough to avoid yield reductions. Depending upon what other crops are included in the rotation, however, you may want to follow a good nutsedge control program in soybeans to reduce problems in the rotational crops.
If nutsedge is a problem, it is important to determine whether it is yellow or purple nutsedge because management programs for the two species may differ. Dual or Vernam preplant incorporated is effective on yellow nutsedge. Adequate control of light infestations of yellow nutsedge may be obtained with Dual applied preemergence; however, control is more consistent and better when the Dual is incorporated. Lasso or Partner suppress yellow nutsedge, but control is usually less effective than with Dual.
Turbo is a packaged mixture containing metolachlor and metribuzin (the active ingredients in Dual and Sencor, respectively). High rates of Turbo, 2.4 pints or more per acre preplant incorporated, will control yellow nutsedge. However, these application rates may result in severe soybean injury on lighter soils. Broadstrike plus Dual is a packaged mixture containing metolachlor and flumetsulam. Broadstrike plus Dual at rates of 2 pints or more per acre preplant incorporated will also control yellow nutsedge.
Yellow nutsedge can be controlled postemergence with Basagran or Classic. Apply 1.5 to 2 pints of Basagran plus 2 pints of crop oil concentrate per acre when the yellow nutsedge is 6 to 8 inches tall. If needed, a second application at the same rate can be made 7 to 10 days later. As an alternative, apply 1/2 to 3/4 ounce of Classic per acre with a surfactant when nutsedge is 2 to 4 inches tall.
Vernam or Pursuit preplant incorporated alone or in combination usually provide sufficient control of purple nutsedge to avoid yield reductions. Pursuit is the only option for postemergence control of purple nutsedge. Apply Pursuit 70 DG or Pursuit 2L at 1.4 or 4 ounces per acre, respectively, with surfactant or crop oil when the purple nutsedge is 1 to 3 inches tall.
Pursuit will suppress yellow nutsedge, but it is more effective on purple nutsedge than on a yellow nutsedge.