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The Right Time for Harvest Aids

As soybean harvest gets into full swing, harvest aids can serve multiple purposes. In some instances, harvest aids are used to dry the green tissue in pods, leaves and stems on mature soybean plants to create a more rapid and efficient harvest. 

They can also be used to manage emerged weeds that may interfere with harvest. However, the weed-control benefits are highly dependent on the herbicide used, weed size and application timing. 

Timing is crucial when it comes to applying a harvest aid to a crop. If a desiccant is applied too soon, it can reduce overall yield because pods may not have enough time to mature fully. Yield may also be adversely affected if a harvest aid is applied too late, as mature pods can shatter.

If applied to late, there will not be enough time to account for the required preharvest interval (PHI) that may be designated on the label for some desiccants.

There are two acceptable methods to time application of harvest desiccants: 

Method 1: According to the labels of commonly used harvest-aid products, harvest desiccants should be applied to indeterminate varieties when 65 percent of the pods have reached a mature color or when seed moisture is 30 percent or less. For determinate varieties, apply when plants are mature or when beans are fully developed, 50 percent of the leaves have dropped and remaining leaves are yellowing. 

Method 2: Desiccants can also be applied when the average seed-moisture content is 40 percent or lower, roughly at the R6.5 growth stage. According to research conducted at the Louisiana State University (LSU) Ag Center, applying the harvest aid at 40 percent seed-moisture content will result in earlier harvest and will not reduce yield. This may be outside what is recommended on common labels, but LSU research determined that waiting until seeds are drier than 40 percent moisture content will not allow the necessary time between its application and the earliest time harvest can occur.