NC State Extension

Responsible Herbicide Use

When used properly, herbicides are environmentally safe. If improperly used, they can enter surface water and groundwater. The practices outlined in the following paragraphs are practical ways to avoid contamination of water supplies with herbicides.

Follow label directions. Most herbicide labels contain specific information related to potential environmental hazards. Read and carefully follow all such precautions.

Do not mix near wells; avoid spills and back-siphoning. The most common causes of groundwater contamination with herbicides are the mixing of herbicides and loading of sprayers near wells, spills, and back-siphoning into wells. To avoid these potential problems, haul water to the field in a nurse tank and then mix and load at the field site. If this is not possible, fill your sprayer at least 50 feet from the well. If filling directly from the well, an antiback- siphoning device should be installed on the hose. Never leave a sprayer unattended while it is being filled. A properly constructed mixing pad to contain any spills is highly recommended.

Calibrate sprayers accurately. Carefully calibrate your sprayer at the beginning of the season and recheck the calibration periodically during the season. Inaccurate calibration can lead to poor weed control if your sprayer applies less than the desired amount of herbicide or it can lead to crop injury if an excess is applied. Applying excess herbicide may also increase the potential for environmental contamination. See your county Extension agent for information on sprayer calibration methods.

Mix the right amount. Before mixing, calculate the amount of spray solution needed and mix only that amount so that you will not have excess to discard. If a small amount of spray solution is left over, dispose of it by spraying it across edges of the field or on the turn rows. Alternatively, if the herbicide is one to which soybeans have good tolerance, dilute the excess spray solution with additional water and spray it out in the treated field. Never dump excess spray solution anywhere.

Rinse in the field. After completing the spraying operation, rinse the sprayer at the field site rather than near your well. Spray the rinse water onto the treated field.

Follow good soil conservation practices. The most common cause of surface water contamination with herbicides is runoff from fields during heavy rains. Good soil conservation practices not only reduce soil erosion and increase availability of water to the crop but also reduce pesticide and nutrient runoff from fields. Avoid spraying when rainstorms are imminent.

Dispose of containers properly. During the mixing operation, triple rinse or pressure rinse empty herbicide containers and pour the rinse water into the sprayer tank. Then punch holes in the bottom and sides of the containers and crush them. Place properly cleaned containers in the county solid waste collection system or take them to the county landfill. As an alternative, if your county has a pesticide container recycling program, take properly rinsed containers to the collection site. Do not burn containers or dump them in unapproved sites.

Use of herbicides in returnable containers or in water-soluble packaging that can be added directly to the spray tank eliminates the problem of container disposal.

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