Agronomy

The difference between drift and volatility

Farm equipment spraying herbicide

Jun 30, 2020

Getting the most out of an herbicide application not only includes maximizing efficacy, but also minimizing damage caused by herbicides. Being aware of what can go wrong and how to avoid it can lead to effective, on-target herbicide applications and help growers have a successful growing season – without the distress and loss caused by applications gone awry.

Two threats to herbicide applications are drift and volatilization. While they may seem similar, they are unique and require different attention to ensure that neither occur.

Drift

Drift occurs during the herbicide application. It is the unintentional, off-target application of herbicides. This can lead to damage of surrounding crops, as well as an ineffective herbicide application.

Several factors that can lead to herbicide drift, including:

  • Severe temperatures: Ideal temperatures for herbicide use range from 65 to 85 degrees F.
  • High wind speeds: Herbicide labels specify optimal wind conditions for application. If a grower goes off-label, the risk of drift increases.
  • Small droplet size: Smaller droplets are more likely to be carried by the wind than larger droplets. Herbicide labels specify optimal droplet size to decrease drift.

Herbicides are most effective when applied in high humidity and with wind speeds of about 10 mph or less. Ensure that application nozzles are on the correct setting to produce optimal droplet size to minimize drift. The position and height of the boom are also listed on the herbicide label. With the boom is closer to the crop, the distance herbicide droplets can travel is reduced.

Volatilization

Volatilization is the movement of herbicide vapors through the air following an herbicide application. Similar to evaporation, volatilization occurs when the herbicide residue changes from a solid or liquid to a gas or vapor. Vapors can be carried long distances by the wind, possibly damaging surrounding crops reducing effectiveness ofthe herbicide application.

Volatilization risk increases when:

  • Herbicides are applied to inert, non-absorbent surfaces like rocks or pavement.
  • Temperatures are high.
  • Humidity is severe.
  • Herbicide formulations are potentially volatile.

Reducing the risk of volatilization is vital for a successful herbicide application. Growers should be sure to avoid unfit conditions, including high temperatures and humidity. Identifying when the target has a nonabsorbent surface or herbicide formulations may be volatile can help growers make proactive decisions regarding tank mixers.

Herbicide specs are not one-size-fits-all. When it comes to avoiding drift and volatilization, herbicide labels are king. By following the label closely, growers will be able to maximize their herbicide applications and reduce risk of drift and volatilization. CHS Agronomy offers a variety of herbicide products.