Increase of herbicide-resistant weeds has led to a renewed emphasis on preemergence herbicides applied within a few days of soybean plantings. The availability of many products and combination products has increased concerns about
crop safety. In addition, soybean planting dates have occurred earlier for many operations that further increase the likelihood of soybean injury from preemergence herbicides.
UD Weed Science Program has not looked at crop injury in a systematic method in the past ten years; nor has any of the regional universities. Information from other regions is not appropriate for Delaware due to our soil type and production practices. There is a need for this type of research.
Many of our trials are planted in mid- to late-May to maximize weed pressure and better evaluate weed control. Ratings and notes on soybean injury from preemergence herbicides are taken in all of our trials; but with the later planting dates that we use the potential for herbicide injury is reduced. When we do observe injury, often times there is a limited number of herbicides in the trial and it is difficult to draw conclusions across a range of active ingredients.
Information on soybean sensitivity to herbicides is lacking. For instance, Pioneer® Seed is one of the few companies that makes this information available in their agronomic tech sheets. It is much more common for corn hybrids to supply this
information than for soybeans. As a result, there is little information that soybean farmers and consultants can rely upon to make decisions on herbicide selection.
It is also challenging when trying to design this type of experiment. A comparison of more than one soybean variety is critical to determine the consistency of results across a range of genetics. However, when changing a variety to develop a
range of varietal sensitivity, it is not possible to keep other variables consistent. As a result, this type of research often sacrifices other agronomic attributes to achieve a range of herbicide sensitivities. As a result, information needs to be compared on a relative basis, which herbicides are most likely to cause crop injury. To determine sensitivity of individual soybean varieties to such a range of herbicides is beyond the scope of this project.
This proposal was developed based on the priorities outlined by the Delaware Soybean Board in their request for proposals as well as conversations with soybean farmers and ag businesses. This research will benefit Delaware’s soybean growers and the soybean industry by knowing potential for crop injury when using preemergence herbicides. In addition, this project was designed to address weed control in terms of effectiveness, adaptability to Delaware’s specific needs, as well as herbicide-resistance management.