As we roll into and quickly through August, I usually cycle this topic back to the top with any updates as consider that the time for making the desiccation decision is quickly approaching.
Planting date, maturity group, stress, and in-season management practices will influence how healthy or “alive” a plant is when the pods hit physiological maturity (R6.5). A well-timed harvest aid application can put a combine in the field quicker, increase harvest efficiency, and decrease environmental impacts from inclement weather conditions during this part of the season.
Soybeans are annual plants – they grow, mature, senesce, and die all in a single season and all on their own. Therefore, they do not require harvest aids in order to harvest. However, that doesn’t mean you shouldn’t consider utilizing harvest aids to your benefit on your soybean acres. As the proportion of soybean planted early (a relative term) in Tennessee increases, you may notice that some fields, particularly those under irrigation or in years with consistent rainfall, with optimum fertility/high management scenarios, etc.. stay green(er) into physiological maturity (R6.5), which is when the soybean within the pod separates from the pod wall membrane.
In these scenarios and at this time, the application of a harvest will put a combine in the field sooner than allowing the plants to dry down on their own. However, delaying harvest aids until after R7 will most-likely delay harvest operations. With a single exception, all harvest aid products have a labeled pre-harvest interval (PHI) that must be followed post-application. Defol 5 (sodium chlorate) has a suggested range of harvest dates post-application. However, since it is a true desiccant (not a herbicide), there is no strict PHI.
I frequently use Sharpen, Defol 5, and Gramoxone each year in various trials and situations. They all can and do work well in certain scenarios. However, if I had to pick just one to cover all plant and environmental conditions, it continues to be Gramoxone.
Defol 5 works well, but needs a full 14 days post-application.
Sharpen also does an excellent job if partial defoliation has already occurred. However, if the plant canopy is dense with minimal defoliation prior to application, I usually see Gramoxone do a quicker job.
