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Using Corn Herbicides and Protecting Water Quality

Guidelines for Corn Producers

Using Corn Herbicides and Protecting Water Quality

Best Management Practices for New York Producers

Corn Herbicide

Best Management Practices (BMPs) are a significant part of an agricultural chemical management plan. BMPs are designed to minimize the potential for adverse impacts on the environment while maximizing the beneficial effects of pesticide use. BMPs are economical and environmentally sound measures that, when followed, will aid in the protection of water resources and ensure the continued availability of modern pesticide production tools such as corn herbicides. While the BMPs recommended in this program focus on corn herbicides, they are equally valuable for other pesticides.

Learn All You Can

Attend a corn herbicides Best Management Practices workshop in your area. Know the products you're using or that are being used on your fields. Develop your management plan, taking into account conditions within the fields where corn herbicides will be applied.

Corn Herbicide Product Description

Corn herbicides are herbicides applied for the preemergence and postemergence control of annual grass and broadleaf weeds in corn. A listing of weeds controlled by corn herbicides can be found on the product label.

Corn Use Information

Corn herbicides are herbicides applied for the control of annual grass and broadleaf weeds. Corn herbicides may be preplant surface applied, preplant incorporated, applied as a preemergence treatment in water or liquid fertilizer, impregnated on dry bulk fertilizer or applied as a postemergence application. Corn herbicides control broadleaf weeds during germination or soon after emergence and grass weeds during germination. Susceptible weeds exposed to corn herbicides either die or remain noncompetitive with the crop. Because the herbicidal activity of corn herbicides on broadleaf weeds involves uptake and translocation to weed growing points, adequate soil moisture is necessary for optimal activity. Corn herbicides may provide residual control of susceptible broadleaf weeds which emerge after application.

General Crop Protection Best Management Practices

Know Your Fields and Farm

  1. Conduct your own Farm Site Evaluation. Use the information to develop your Best Management Practices and plan.

  2. Maintain field records:

    1. Scout fields to identify weed species and population levels.
    2. Select herbicides and application rates based on soil type, organic matter content, soil permeability, soil pH and depth to ground water. Also, consider types and populations of weeds present or anticipated.
    3. Record soil test results, crop planted, weed problems, pesticides used (active ingredient, rate), application dates, weather and results.
    4. Identify highly erodible fields and their drainage patterns.

  3. Use the most appropriate tillage and herbicide practices for your crop and field characteristics (soil type, past weed problems, environmentally sensitive areas etc.).

  4. Consider crop rotations, if appropriate, to reduce weed competition and to lessen the chances for resistant weed biotypes to spread.

  5. If you participate in a soil conservation or water quality program, follow prescribed recommendations.

  6. Work with your dealer or applicator and evaluate your fields before the planting season. Additional information may be obtained from the Cooperative Extension Service or the Soil Conservation Service.

Mixing and Loading

  1. Ideally, mix and load agricultural chemicals and rinse equipment on an impervious surface (containment pad).

  2. Mix and load pesticides and rinse equipment in the field if you don't have a containment pad, and vary the location. Stay away from any well (including drainage wells and abandoned wells), stream or sinkhole during mixing and loading operations. Follow any additional state and label requirements.

  3. Do not mix or load agricultural chemicals near public drinking water supply wells unless you're using a containment pad. Follow any additional state requirements.

  4. Clean up chemical spills (even small ones) immediately. Don't let the material soak into the ground. Have spill material (cat litter, sawdust, etc.) available when mixing and loading.

  5. While filling your spray tank, make sure there's a fixed air gap (air break) between the water source and the tank or an antibackflow device on the fill hose. During filling operations, don't allow the water to be back-siphoned. Keep the end of the fill hose above the surface of the water/chemical solution in the tank at all times.

Container and Equipment Cleaning

  1. Minimize container and equipment cleanup needs by mixing only enough product for the job at hand.

  2. Always start with a clean, calibrated sprayer that can provide appropriate agitation.

  3. Clean containers and equipment at the application site if you don't have a mixing and loading pad. Put the rinsate in your spray tank and apply evenly over a field or dispose of as the label specifies.

  4. Rinse product containers immediately. Delays can result in residue drying and becoming much more difficult to remove.

  5. Pressure- or triple-rinse disposable containers immediately after emptying. Be sure to add the rinsate to the spray mix. Puncture the containers before disposing of them.

  6. Participate in container recycling programs for empty disposal containers when offered in your area.

  7. Properly dispose of rinsed pesticide containers that cannot be refilled or recycled. Do not burn pesticide containers.

  8. Stay away from all wells including abandoned wells, drainage wells and sinkholes when mixing, loading, rinsing or washing containers and equipment unless these operations are carried out on an impervious pad. Follow any other applicable state requirements.

Background Information -- Guidelines For Corn Producers Using Corn Herbicides And Protecting Water Quality

The United States Environmental Protection Agency (EPA), under mandates of the Clean Water Act (CWA), is requiring states to develop comprehensive water quality management plans to restore water quality where degradation has taken place, maintain quality and eliminate contamination. EPA has provided a role for states that grants flexibility to fit the solution to the problem and provides funding to assist in development of management programs to address water quality issues.

Components of the CWA management plans address point source pollution, nonpoint source pollution (farming) and dredge and fill operations. The CWA was amended by Congress to address water quality impacts from storage tanks, added wellhead protection, protection of sole-source aquifers and protection of groundwater.

To protect groundwater, states have been asked by EPA to develop a generic management plan that tells how the state will set about the task of implementing a protection program. In New York State, this plan has been developed by the New York State Department of Environmental Conservation's (NYSDEC) Division of Water and is available for review. The next step in the process is for EPA to identify and label agricultural chemicals that have a potential to leach to groundwater. It will become the responsibility of the states to develop and implement chemical-specific management strategies and enforce those strategies. Under EPA's current proposal, if a state fails to develop management plans to protect groundwater, use of those chemicals could be denied. While enforceable requirements are not expected until the 1998 growing season, there is considerable merit to initiate protection initiatives in advance of these new regulations.

The DEC, along with a coalition of New York Corn Growers, New York Farm Bureau, Agriculture and Markets, Cornell University, New York State Agribusiness Association and manufacturers, developed a voluntary management plan that addresses groundwater protection for all corn herbicides registered for use in the state of New York. Management practices utilized for one material are equally appropriate for all products. The emphasis of a voluntary best management plan is on prevention of contamination.

Groundwater protection is your business. As a farmer, you and your family rely on groundwater for drinking. Protection of this resource maintains the value of your farm and will preserve the availability of crop protection chemicals for your use. The coalition has prepared a best management plan that you can follow in selecting and using corn herbicides on your farm. We urge you to adopt this approach in your farm planning practices.

Map of NY Aquifers

Best Management Practices Planning Your Way To Water Quality Protection

Determine if the fields where you intend to use corn herbicides are within the shaded areas. These areas are thought to have highly permeable, coarse soils underlain by ground water that is near the surface. Locations outside the shaded areas indicated on the map also may contain coarse soils and shallow ground water.

Corn Herbicides State-Specific Best Management Practices and Plans

  1. Conduct a Farm Site Evaluation to determine conditions, practices and areas on your farm that may present potential ground water concerns.

  2. If the Farm Site Evaluation reveals soils (classified as sand or loamy sand soil) and the ground water table is shallow, use the lower recommended rates or consider alternative weed control practices.

  3. Read the corn herbicides label thoroughly reviewing, in particular, parts relating to personal protection equipment, rotational crop restrictions, spray drift avoidance practices, pH limitations, and antisiphoning device utilization.

  4. Select appropriate rate and application techniques and, if applicable, tank-mix partner.

  5. Calibrate application equipment prior to use. Use equipment that is capable of continuous and vigorous tank agitation (rippling or rolling action at liquid surface).

  6. Always start with a clean, calibrated sprayer.

  7. Pay particular attention to rotational crop restrictions and precautions.

Pesticide Best Management Practices

Farm Site Evaluation

Here's a list to help you determine if you're using Best Management Practices (BMPs) which help protect ground water and surface water. Please take the time to review the conditions within the corn growing areas on your farm while referring to the list.


  1. Do you always read and follow the appropriate instructions on the pesticide label? Yes No

  2. Do you scout your fields for weeds every year before deciding what herbicide and application rate to use? Yes No

  3. Do you maintain field records of pesticide applications? Yes No

  4. Do you consider alternate means of suppressing hard-to-control weeds (those that may have become resistant to your usual herbicide), rather than simply increasing rates? Yes No

  5. Are you aware of the location of wells, abandoned wells, bodies of water, ponds and streams in your fields? Yes No

  6. Do you know the percentage of the soil surface that is sand or loamy sand in fields where you intend to use corn herbicides? Yes No

  7. Do you know the general depth of the water table (ground water) in the vicinity of the fields? Yes No

  8. Soil pH can have a significant impact on herbicide performance. Do you know the pH in all fields where you intend to use corn herbicides? Yes No

  9. If appropriate, do you maintain grass or other types of buffer strips between the edges of your fields and runoff points that drain into bodies of water or streams? Yes No

  10. If you farm on highly erodible soils, are you following all proper water quality protection measures? Yes No

  11. Do you have a map identifying areas in your county or on your farm that may be vulnerable to water quality concerns? Yes No


  1. Do you follow recommended methods for disposal of pesticide containers? Yes No

  2. Do you have an emergency plan and the necessary equipment to handle an accident (fire or spill) where you have pesticides stored? Yes No

  3. Are your pesticides stored in a locked building, and do you have written records of the products stored? Yes No

  4. Have you taken extra precautions to protect the areas around wells on your farm? Yes No

  5. Do you inspect and maintain your wells and plumbing connections on an annual basis?Yes No

  6. Do you use devices to prevent back siphoning or back flow on fill hoses connected to wells or other water supplies? Yes No


  1. Do you have a containment pad with an impervious surface? Yes No

  2. If you mix and load pesticides in the field, do you vary the location each time? Yes No

  3. Do you follow directions on the product label for proper disposal as soon as containers are emptied? Yes No

  4. Do you clean up small spills as soon as they occur? Yes No

  5. If you clean tanks and spray equipment in the field, do you change the location every time? Yes No

  6. Do you always check to be sure field location where you mix and load pesticides or clean application equipment is away from any well, stream or lake? Yes No

  7. Are all people who handle pesticides on your farm properly trained? Yes No
If you checked (No) to any of the questions, please determine Best Management Practices designed to address the particular point made in the question. Contact your local Cooperative Extension Agent for information on the practices you should be following. The Corn Herbicides Management Plan and training program provide effective examples.

If you use a custom applicator or dealer who offers a full service program, he or she can inform you of steps you can take to protect the water resources on or near your property. You also may contact your state lead pesticide agency or your local Ag chemical representative for more information.