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Pre-Harvest Grain Sorghum Weed Control Application

Posted 7/21/2017
Why Use a Pre-Harvest Application of a Roundup® Brand Agricultural Herbicide?

Why Use a Pre-Harvest Application of a Roundup® Brand Agricultural Herbicide?

  • Roundup® brand agricultural herbicides (Roundup PowerMAX®, Roundup PowerMAX® II, and Roundup WeatherMAX®) are registered for pre-harvest use to kill weeds and terminate grain sorghum plants.
  • Killing foliage can allow for earlier harvest.
  • Grain moisture at harvest may be reduced.
  • Less green matter can help increase harvest efficiency.
  • Late-season weed control can help reduce late-season weed seed production.
  • Late-season water uptake from the sorghum and weeds may be reduced, resulting in the potential for more soil moisture for the next crop.

Roundup Brand Agricultural Herbicides Pre-Harvest Application Recommendations for Grain Sorghum

When–Apply a Roundup brand agricultural herbicide when grain sorghum is at 30% moisture or less. Physiological maturity occurs when a “black layer” forms at the base of grain berries. Tiller heads may mature later than primary heads.

Rate–Apply 22 to 32 fl oz/acre. Do not apply more than 44 fl oz/acre.
By ground application equipment at 5 to 10 gal/acre.
By aerial application at 3 to 5 gal/acre.
Add ammonium sulfate (AMS) at 8.5 to 17 lbs per 100 gal of spray solution.

Restrictions–Allow a minimum of 7 days between application and harvest of grain sorghum.

Application Restrictions

Roundup brand agricultural herbicides should not be used pre-harvest on sorghum grown for seed as a reduction in germination or vigor may occur. After an application of a Roundup brand agricultural herbicide, sorghum should not be harvested for a minimum of 7 days and it may take from 2 to 3 weeks for the herbicide to completely kill the sorghum plant. Making a pre-harvest application too early may reduce grain quality and yield potential.

When applying a Roundup brand agricultural herbicide pre-harvest, if grain sorghum is drought-stressed, diseased, or lush due to irrigation, it is recommended to increase the application towards the higher end of the labeled herbicide rate and add a full rate of AMS (17 lbs/100 gal of spray solution). Avoid a pre-harvest application of a Roundup brand agricultural herbicide if sorghum is infected with charcoal rot as lodging may occur.

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