With postemergence herbicide applications in soybeans in full force throughout many parts of the state, a few things need to be considered before making these applications.
Clean Application Equipment
In many cases, equipment that is going to be used for spraying postemergence soybean herbicides has just been used in spraying a postemergence corn herbicide. When making this transition between corn and soybeans, make sure that the application equipment is thoroughly cleaned. Several corn herbicides can leave residues in equipment that may be brought back into solution once the spray tank is filled. These residues can cause damage to soybeans. Labels of many postemergence corn herbicides provide techniques for cleaning application equipment to ensure that these residues aren't left in the spray tank. Remember to thoroughly clean the spray boom, nozzles, and screens as well.
Apply the Appropriate Rate
With the varying sizes in weed growth in relation to soybeans, it is important to apply the appropriate herbicide rate for maximum weed control. This is particularly important in fields that did not receive a burndown herbicide application or where preplant tillage did not fully control the initial weed growth (i.e., common lambsquarters). Weeds in these fields are going to have more growth and be larger and will need higher application rates for effective control. So make sure to adjust the application rate according to the maximum weed size in the field.
Select the Proper Additive
The selection of herbicide additives is often specified on the respective product label, but many postemergence soybean herbicides allow the use of a nonionic surfactant (NIS), a crop oil concentrate (COC), or a methylated seed oil (MSO), with or without a nitrogen fertilizer. For many products, NIS may be the preferred additive, but COC may be used under very dry conditions to enhance weed control. Remember, when using a COC or MSO instead of an NIS, there is an increased chance for crop-injury potential for several postemergence soybean herbicides.--Christy Sprague and Aaron Hager