How a Desiccant Can Aid Harvest and Protect Yield for Soybeans

Wade Givens, Ph.D.

Oct 04, 2019

Soybean harvest might be a bit more challenging for farmers this fall.

For one, record-breaking rainfall and prolonged flooding in the spring kept many farmers out of their fields until much later, leading to a later harvest.

Second, spot planting and planting behind receding flood waters will impact how uniform your soybean plants will drop their leaves and be ready for harvest.

If you’re concerned about timeline and protecting your yield, this might be a good year to use a desiccant to help prep your soybean crop for harvest activities.

Three desiccant options for soybean fields

You have several choices when selecting a desiccant application. Here are some products (and recommended application rates) labeled for use as a harvest aid in your fields:

  • Paraquat (at 0.125-0.25 lb ai/acre)Paraquat activates desiccation of both weeds and soybean plants. The preferred application rate is 0.25 lb ai/acre, and you should include a nonionic surfactant (0.25 percent V/V) with the application. For paraquat, a 15-day preharvest interval is required.

  • Saflufenacil (at 1-2 fl oz/acre)

    Broadleaf weeds and soybean plants will experience desiccation when saflufenacil is applied. The addition of a methylated seed oil (one percent V/V) plus ammonium sulfate (one-two percent W/V) is recommended for optimal desiccation. Application rates of 1.5-2 fl oz/acre are generally required when saflufenacil is applied alone. This product has a three-day preharvest interval.

  • Sodium Chlorate (at 6 lb ai/acre) Sodium chlorate will provide desiccation of weeds and soybean plants, but activity level from this application will depend on environmental conditions. As a true desiccant, sodium chlorate will physically draw moisture out of plant tissue and seed and should be applied 7-10 days before harvest.

You’ll want to factor the specified preharvest interval for the desiccant you select into your timeline. In addition, a greater application volume (20-30 GPA for ground applications and 4-10 GPA for air applications) is recommended when making a harvest aid application in soybean fields, as complete coverage is essential.

Things to consider before applying a desiccant

Before you apply a harvest aid in your fields, check the forecast in your region. Weather may influence the time required for proper desiccation, and wet field conditions can delay harvest activities altogether. 

It’s also important to pay attention to the stage of your soybean crop. The more green material you see, the longer you’ll need to wait for your crop to reach full desiccation and be harvest ready (Pro tip: Focus on the color of the pods rather than the leaf color of your soybean plants for an accurate assessment).

Apply the desiccant when your soybean crop is mature enough so that the seed isn’t affected by premature termination. Your seed pods should be brown in color, or at least turning yellow.

Once the majority of the pods in the field are mature (with the remaining pods having seed completely separated from the pod wall), it is safe to apply a harvest aid.  

With indeterminate soybeans, your plants should be “mature and ready for harvest” according to the sodium chlorate label, or “when 65 percent of pods are mature brown color or when seed moisture is 30 percent or less” per the paraquat label. 

Know the limits of a desiccant

A harvest aid will not change the maturity of the crop, it only enhances dry down in a mostly mature field of soybeans. 

If a desiccant is sprayed when pods are too young (i.e., green pods, seed are not full-sized and are not separating easily from the pod wall), seed will not mature normally and often show up as “butter beans” and damaged seed at harvest.

Looking for a specific soybean desiccant product?

With FBN Direct, you can purchase product online and and get it delivered straight to your farm. 


Wade Givens, Ph.D.

Oct 04, 2019