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Best Practices

Herbicides pose risks to people, wildlife, and the environment when misused. However, with proper handling and precautions, these risks can be minimized. Responsible herbicide use involves not only following label instructions but also applying them selectively in natural environments. Ensuring equipment is well-maintained is also essential for safe application [1].

How To Maintain Herbicide Application Equipment

Follow the manufacturer’s recommendations for routine maintenance.

Maintenance should include proper lubrication and calibration of equipment, regular inspections of seals, hoses, pumps, and gaskets. Replacing worn or damaged parts, and storing it properly to prevent corrosion or damage [1].

If you use oil-based herbicides (ex: Garlon 4, Element 4, and Tahoe 4) in the sprayers, ensure you are washing and inspecting after each use. This is because the formulations contain petrochemicals which can break down the equipment seals. After spraying water-soluble herbicides, if you cannot clean your sprayers, at a minimum rinse them with clean water to keep the lines and nozzles free of clogs [1].

Squeeze bottles should be emptied at the end of each workday to ensure accurate herbicide use records and to prevent leaks caused by temperature changes. Always keep a safety pin or paper clip nearby to clear clogs in the nozzle tip. Never attempt to unclog a spray tip by blowing through it [1].

How To Calibrate Equipment

Calibration is the process of measuring and adjusting your equipment to ensure it applies the correct amount of pesticide over a specific area. It’s an essential first step to make sure pesticides are distributed evenly and at the proper rate. Remember to always read and follow all of the pesticide label information.

Considerations

Considerations

Calibrate with water first, then mix the pesticide. Repeat calibrations regularly (every season or when any part of the system changes). Factors like herbicide type, vegetation height, wind conditions, and desired spray width should be considered when choosing the appropriate nozzle system and operating procedures. You save money and time by avoiding over and under-application of the pesticide. You also protect the environment by reducing residue in the soil and water.

Equipment Condition

Nozzle Condition: Check for clogs, wear, and uneven spray patterns.
Pressure Consistency: Ensure consistent pressure for uniform application.
Hose Leaks & Connections: Inspect for leaks or damage that affect output.
Tank Agitation: Especially important for liquid suspensions or wettable powders.
Boom Leveling (for boom sprayers): Uneven booms = uneven application.
Spray Width (boomless): Must be measured accurately—can change with wind, pressure, terrain.

Operator Practices

Walking/Driving Speed: Must be consistent. Calibrate your pace or vehicle speed.
Spray Height: Maintain the recommended height for uniform distribution.
Spray Technique: For handheld, ensure overlapping, consistent strokes.
Repeatability: The time you spray over the test area must match your field pace exactly.

Environmental Conditions

Wind: Can drift the spray, especially for fine droplets or boomless sprayers.
Temperature & Humidity: Can affect evaporation and drift.
Terrain: Slopes may affect pace and spray coverage.

Pesticide Properties

Formulation Type: Some products (e.g., ECs vs. WPs) require better agitation.
Label Rate: Follow the product label—it’s the law.
Tank Mix Compatibility: Make sure your mixture won’t clog nozzles or settle.
Target Pest/Crop: Your application volume may vary based on pest pressure or canopy density.

Test Before Field Application

Run water-only calibrations first.
Measure the output before using the pesticide.
Test on dry surfaces to assess spray width and pattern.

Area Measurement Accuracy

Misjudging square footage leads to over- or under-applying.
Use flags or chalk lines to mark test areas accurately.
GPS tools can help with large-area calibration.

Safety First

Wear appropriate PPE Personal Protective Equipment (PPE), a general term for protective clothing, helmets, goggles, or other gear designed to protect the wearer from injury or infection. It’s used in various settings to minimize exposure to hazards. even during water-only calibration (gloves, goggles).
Keep others and animals away from the test and application area.
Properly label and clean any measuring containers used.

1/128 Method (for handheld or backpack sprayers, boom sprayers, and boomless sprayers)

The 1/128th calibration method is a simple way to determine the amount of pesticide to apply per acre by measuring the output from a sprayer over a 1/128th acre area. This method works by relating the number of fluid ounces collected from the sprayer to the number of gallons per acre. It works best for hand-held or backpack sprayers and boom sprayers.

1/128th Acre:
The method focuses on spraying a small area, approximately 340 square feet, which represents 1/128th of an acre.
Fluid Ounces and Gallons:
Since there are 128 fluid ounces in a gallon, the number of ounces of spray collected from the 1/128th acre area directly corresponds to the gallons per acre (GPA) application rate.

Boomless Sprayer

Procedure:

Measure the Area

Determine Spray Width

Operate the sprayer briefly over a dry surface like concrete or cardboard at your normal speed and pressure.
Measure the total visible spray width (from one edge of coverage to the other). (Example: 20 feet)

Calculate the Length of the Test Strip
Use the formula: Length = 340 ÷ Spray Width (Example: 340 ÷ 20 = 17 feet)

Mark Out the Test Strip

Length = calculated value (ex: 17 feet)
Width = your spray width (ex: 20 feet)
This gives you an area of 340 square feet, which equals 1/128 of an acre

Time the Spray

Fill the sprayer tank with clean water.
Spray the marked test area using your normal operating speed and pressure.
Record the time (in seconds) it takes to spray the entire strip.

3. Collect the Spray

With the sprayer stationary, use the same throttle and pressure used in the field.
Spray into a measuring container for the same number of seconds you recorded in the previous step.

If using multiple nozzles, either:

Collect output from all nozzles during that time, or Divide the time between nozzles and add the totals.

Measure the total volume of water collected in fluid ounces.

4. Calculate GPA (Gallons per Acre)

The number of ounces collected equals the gallons per acre (GPA).
Ounces collected = Gallons per Acre (GPA)

Examples

Example 1:
Spray Width = 20 ft
Length = 340 ÷ 20 = 17 ft
Time to spray test area = 15 seconds
Volume collected in 15 seconds = 12 ounces
GPA = 12

Boom Sprayers

Procedure:

Measure the area:

1. Measure total boom width in feet (Example: 20 ft)
  - Boom Width = Number of Nozzles × Nozzle Spacing
  - If you’re not sure of nozzle spacing, some nozzles are shut off or damaged, or the boom doesn’t have even spacing, use a measuring tape.
    - - If you are using a measuring tape:
        
        Lay the boom flat and measure from the first nozzle to the last, measuring only the active spray width.
        
        Only count the width actually being sprayed. If one nozzle is turned off (like for fence-line spraying), don’t include that nozzle in your width.
        
        Always measure nozzle spacing center to center.
2. Calculate the length of the area to spray: Lenght = 340 ÷ Boom Width (Example: 340 ÷ 20 = 17 ft)
3. Mark out a test strip: Length = calculated value (ex: 17 ft), Width = your boom width (ex: 20 ft), (Example: 20 ft wide by 17 ft long = 340 sq ft)

Time the spray:

1. 1. Fill your tank with clean water.
  2. Spray the test area at your normal operating speed and pressure.
  3. Record the time (in seconds) it takes to spray the full test strip.

Collect the spray:

1. With the sprayer stationary, use the same pressure and throttle.
2. Spray into a measuring container for the same number of seconds recorded in step 2.
  - Tip: If you have multiple nozzles, collect from all, or divide time evenly among them, and add the totals.
3. Measure the total volume of water collected in fluid ounces.

Calculate GPA:

The number of ounces collected equals the gallons per acre (GPA).
Ounces collected = Gallons per Acre (GPA)

Example 1:
If you collect 30 ounces of water while spraying 1/128th of an acre, your sprayer is calibrated to apply 30 gallons per acre.

Example 2:

Boom Width = 20 ft
Length = 340 ÷ 20 = 17 ft
Time to spray test area = 15 seconds
Volume collected in 15 seconds = 12 ounces
GPA = 12

Handheld or Backpack Sprayer

Procedure:

Measure the Area:

Determine Spray Width:
- Spray a short test line on dry concrete or cardboard at your normal walking speed and pressure.
- Measure the actual width of the spray pattern (from one edge of visible coverage to the other). (Example: 2.5 feet wide.)
Calculate the Length of Area to Spray:
- - Length = 340 ÷ Spray Width (Example: 340 ÷ 2.5 = 136 ft)
Mark out a Test Strip:
- Length = calculated value (ex: 136 ft).
- Width = your measured spray width (ex: 2.5 ft)
- This gives a total of 340 sq ft, or 1/128 of an acre

Time the Spray:

Fill your tank with clean water.
Spray the test strip at your normal pace and pressure.
Record the time in seconds it takes to walk and spray the entire test area.

Collect the Spray:

With the sprayer stationary, use the same pressure and settings.
Spray into a measuring container for the same number of seconds you recorded when testing it inthe field.
Measure the total volume of water collected in fluid ounces.

Calculate GPA:
Ounces collected = Gallons per Acre (GPA)

Example:

Spray Width = 2.5 ft
Length = 340 ÷ 2.5 = 136 ft
Time to spray test area = 20 seconds
Volume collected in 20 seconds = 15 oz
GPA =15

Air Blast Sprayers

Check speed:
Always check speed in the field as opposed to a gravel road, since the terrain influences speed. There are two ways to assess speed.

Method 1: Manual check
In the field, mark a 100-foot path with two stakes.
Use a stopwatch, and record the time it takes for the front tire of the tractor to pass from one pole to the next.
It’s more accurate to take 2-3 different 100-foot paths, and then take the average of all times, and then calculate miles/hour.

Formula to Use for Dry Formultions

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How To Clean Equipment Safely

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How To Dispose Herbicide Safely

For tanks [3]:

The safest and simplest way to dispose of rinsate Rinsate is a diluted mixture of pesticides with water, solvents, oils, commercial rinsing agents, or other substances.
It’s generated during activities like washing pesticide spray equipment, changing spray mixes, container rinsing, or cleaning out storage tanks. from sprayer tanks is to spray it in the field after pressure or triple rinsing to remove excess chemical residue.
If there is no access to a nearby water source or mobile tank to rinse sprayer tanks away from the farmyard, following the pesticide label directions is best.
A simple rule of thumb: if a product isn’t registered for a crop, don’t spray its rinsate on that crop. Most chemical labels now include company contact details, often with toll-free numbers for technical support during spray season.
When staying within the proper spray window, adjust spraying schedules so that fields needing the same chemical are treated together. This minimizes the number of sprayer tank rinses required. [3]

For equipment [1]:

Minimize the amount of herbicide-contaminated water you have by mixing and washing carefully.
* Remember that water used to rinse out equipment can be used for mixing the next batch of herbicide solution.
Well-diluted rinsate should be disposed of where it is able to bind to mineral soil particles.
*Always decide where your rinsate will be used up or spread before mixing any herbicide.
Consult with your land steward or preserve manager to agree upon where your “waste area” is.
*Consider who will be using the waste area. Will children or pets ever interact with the waste area? [1]

Recordkeeping

Recordkeeping

It is critical and required by NM law to keep records of all plants/areas treated, amounts and types of herbicides used, and dates of applications.

Each state has specific recording requirements. In New Mexico, see the Pesticide Control Act within Chapter 76, Article 4 of the New Mexico Statutes Annotated. A summary of the act can be found here.

Commercial, public, and noncommercial applicators must keep detailed pesticide application records, including the applications made by anyone they supervise. Records must be completed within 24 hours of the pesticide application, kept for at least 2 years, and provided to NMDA or the customer upon written request. Any format is acceptable, as long as all required details are included [2].

The customer’s name;

the date, time, and location of the application;

The name and EPA registration number of the pesticide or pesticides used,

The concentration or rate applied.

The target pest and site (name of crop or specific site);

If the application is made outdoors, the wind direction and speed, and the temperature at the time of the application;

The total volume of mixed pesticide (use-dilution preparation) applied, whenever the pest control category is agricultural, forest, ornamental, aquatic, right-of-way, public health, or wood destroying pest control; and

The name and license number of the individual who applied the pesticide. [2]

Here is an editable Word document you can use.

Citations

[1] J. Hillmer and O. Land, “Upkeep and Maintenance of Herbicide Equipment upkeep and maintenance of herbicide equipment a guide for natural area stewards,” Jun. 2003. Accessed: May 16, 2025. [Online]. Available: https://www.invasive.org/gist/products/library/herbupkeep.pdf

[2] B. Lewis, “New Mexico Pesticide Law Summary,” New Mexico Department of Agriculture. https://nmdeptag.nmsu.edu/pesticides/nm-pesticide-law.html#gsc.tab=0 (accessed May 16, 2025).

[3] Alberta EFP, “How to Dispose of Rinsate from Tanks,” Alberta Environmental Farm Plan, May 30, 2017. https://www.albertaefp.com/blog/beneficial-management-practices-13/how-to-dispose-of-rinsate-from-tanks-54/ (accessed May 21, 2025).

L.L. Berry, Bugwood.org

Fun Facts

Other medicinal uses included relieving ulcers, removing obstructions in the liver and spleen, curing eye discomfort, and relieving various skin ailments such as sores, pimples, “piles,” “scurf wheals,” “ugly sores,” and even leprosy. [8]