Harvest Aid Herbicide Options in Soybean

Harvest Aid Herbicide Options in Soybean

REVISED: Aug. 19, 2022 (originally published Sept. 17, 2020)

As we get close to soybean harvest, some herbicides can be applied as harvest aids (desiccant) to desiccate weeds and improve harvest operation. Glyphosate-resistant waterhemp and Palmer amaranth are widespread and if they were not controlled early in the season, they can interfere with soybean harvest (Figure 1).

While weeds can interfere with harvest equipment, some producers see the benefit of a harvest aid in creating a more rapid and efficient harvest. Soybean can reach physiological maturity but may have an excess of green stems and leaves. Additionally, a harvest aid may allow a producer to get into the field a few days earlier than allowing the plant to senesce naturally. A few factors need to be considered when deciding on a harvest aid, including application timing, avoiding grain loss due to shattering or seed quality decline, pre-harvest interval associated with herbicide application and harvestability due to green stem.

Harvest Aid Herbicide Options in Soybean

Aim (Carfentrazone-ethyl): Apply 1.0 to 1.5 fl oz/acre of Aim 2EC as a harvest aid to desiccate certain broadleaf weeds. It should be applied when soybean is matured, and the grain has begun to dry down. Pre-harvest interval is 3 days. Do not feed treated soybean forage or hay to livestock.

Glyphosate: Glyphosate can be applied to Roundup Ready and conventional soybean after 80% leaf drop. Glyphosate will not be effective for drying out Roundup Ready or Roundup Ready 2 Xtend soybean because they are resistant to glyphosate. Additionally, glyphosate will not be effective on glyphosate-resistant weeds. Apply up to 0.75 lb ae/acre (32 fl oz/acre of a 3 lb ae/gal formulation) in 20 gallons of water/acre to dry out weeds that may interfere with harvest. Allow a minimum of 7 days between application and harvest. Use of a non-ionic surfactant (NIS) plus ammonium sulfate (AMS) in the spray solution to improve control. Do not graze or harvest the treated crop for livestock feed within 25 days of application. Do not use on soybean grown for seed.

Gramoxone SL (Paraquat): Gramoxone is a contact herbicide and should be applied at 1 pint/acre plus nonionic surfactant (1 qt/100 gallons of spray) to soybean that is mature (65% or more of the seed pods have reached mature brown color or seed moisture is 30% or less. A pre-harvest interval of 15 days should be maintained. Do not graze or harvest for forage or hay. Special training is required to apply this herbicide.

Sharpen (Saflufenacil): Sharpen is a broadleaf weed herbicide. Apply sharpen at 1 to 2 fl oz/acre after soybean physiological maturity when greater than 50% leaf drop has occurred and remaining leaves are yellow. Pre harvest interval of 3 days should be maintained. Include MSO plus AMS for better efficacy of Sharpen. Sharpen will not have effect on grass weeds.

Uncontrolled palmer amaranth
Figure 1. Uncontrolled palmer amaranth can interfere with soybean grain harvest. Harvest aid herbicides such as Aim, Glyphosate, Gramoxon, or Sharpen are available to desiccate weeds for smooth harvest. (Photo by Amit Jhala).

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