Get an early start on weed control in soybeans
* Morningglory. Glyphosate sometimes has trouble controlling morningglory. To help get better control, you can use either Authority-based or Valor-based herbicides preplant or preemergence. Liberty can also provide good morningglory control in Liberty Link soybeans.
* Kochia. Kochia is a major weed problem in western areas and has often been difficult to control with glyphosate, especially as it gets bigger. In addition, glyphosate-resistant kochia is becoming a major problem in western Kansas. Since much of the kochia emerges well before soybean planting, one of the keys to managing kochia in soybeans is to control it early in the spring before soybean planting. Research by K-State the last couple of years indicates that several preemergence herbicides can help provide control of glyphosate-resistant kochia, especially the Authority-based products listed above. Early applications of dicamba can also provide effective control of kochia, but the appropriate precipitation and preplant waiting intervals need to be followed to avoid potential soybean injury and stand loss. The Kixor-containing products Sharpen and OpTill may help with kochia burndown, but the Kixor rates that can be used in soybeans will not provide very much residual control. ALS-inhibiting herbicides may or may not provide kochia control because of the occurrence of ALS-resistant kochia.
* Crabgrass and small-seeded broadleaf weeds. Glyphosate usually gives good control of most grasses, but producers may want to apply a foundation herbicide to control grasses early, followed by a postemergence glyphosate application to clean up any escapes. Prefix, Fierce, Intrro, Dual II Magnum, Outlook, and Prowl H2O can all provide good early-season grass and pigweed control ahead of Roundup Ready soybeans. Of these, Prefix and Fierce generally provide the best pigweed control, and Prowl H20 the least. Several residual herbicides, such as Warrant, Outlook, and metolachlor products can be applied as a postemergence tank-mix with glyphosate to provide extended residual control of grasses and broadleaves later in the season. However, it is important to understand that these products do not have postemergence activity, so they will not control emerged glyphosate-resistant pigweeds.
Liberty Link soybeans are an alternative technology to Roundup Ready, especially in the presence of glyphosate-resistant weeds. Liberty can provide effective postemergence control on a broad spectrum of weeds, but good performance is very dependent on several application factors, such as weed size, spray coverage, and humidity. The most successful Liberty Link weed control programs will utilize a good preemergence herbicide treatment at planting, followed by a timely application of Liberty when the weeds are relatively small using a minimum spray volume of 15 gallons per acre to ensure good spray coverage.