Glyphosate is a widely used, non-selective herbicide that controls unwanted vegetation by inhibiting a specific enzyme pathway in plants. It is absorbed through the leaves and translocates throughout the plant, stopping growth and causing the plant to die. Since glyphosate is often sold as a concentrated liquid, it must be accurately diluted with water before application to ensure both effectiveness and safety. Understanding the correct mixing procedure is paramount to achieving successful weed control while protecting the surrounding environment and the applicator.
Essential Safety Precautions
Before opening any container of concentrated glyphosate, personal protective equipment (PPE) must be secured to minimize the risk of chemical exposure. The product label mandates wearing a long-sleeved shirt, long pants, socks, and closed-toe shoes to cover all exposed skin. Chemical-resistant gloves, such as those made from nitrile or butyl rubber, are necessary when handling the concentrate and the mixed solution.
Eye protection, like goggles or a face shield, is required to guard against splashes during pouring and mixing. If the application involves significant spraying or a risk of inhaling fine spray particles, a respirator or mask may be necessary, as specified by the product label. Environmental factors also require consideration before mixing and application. Application should be avoided on windy days, as spray drift can affect desirable plants or contaminate nearby water sources.
Determining the Correct Concentration
The first step in mixing is consulting the product label to determine the concentration of the active ingredient, glyphosate, often listed as a percentage or pounds of acid equivalent per gallon. Concentrate formulations vary widely, meaning a specific mixing ratio for one product may be incorrect for another, potentially leading to poor weed control or product waste. The label provides specific mixing instructions based on the intended target, such as general annual weeds, tough perennial grasses, or woody brush.
For instance, a common 41% glyphosate concentrate might recommend mixing 2 to 4 fluid ounces per gallon of water for general weed control. Tackling more established or difficult weeds, like deep-rooted perennials, requires a stronger concentration, sometimes up to 5 or more fluid ounces per gallon of water. These ratios must be measured to ensure the herbicide is applied at the optimal rate without exceeding the maximum allowable amount. Always calculate the total amount of concentrate needed based on the size of your spray tank and the target weed type to avoid over-mixing and having excess solution.
The Physical Mixing Procedure
The physical process of combining the concentrate and water should always be performed near the application site, not near drains or water sources, to contain any potential spills. Begin by partially filling the clean sprayer tank with clean water, about one-half to three-quarters of the final volume. Use a dedicated measuring cup or device, separate from kitchen tools, to accurately measure the calculated volume of glyphosate concentrate.
Slowly pour the measured concentrate into the partially filled tank, allowing it to mix with the water already present. This initial dilution helps prevent frothing and ensures the concentrate disperses evenly within the water carrier. If the label recommends an adjuvant, such as a non-ionic surfactant or ammonium sulfate (AMS), they should be added after the glyphosate is fully mixed. Adjuvants help the herbicide penetrate the waxy leaf surface or condition the water to improve performance. Finally, add the remaining water to the tank until the desired volume is reached, and then thoroughly agitate the mixture before beginning the application.
Safe Disposal and Equipment Cleanup
Immediately following the application, the sprayer and all measuring tools must be cleaned to prevent corrosion and cross-contamination. The standard cleaning practice is triple-rinsing, which involves three separate rinses of the equipment with clean water. For the first rinse, add a small volume of water—about one-fifth to one-fourth of the tank capacity—to the sprayer, agitate it, and spray the rinse water onto a site labeled for glyphosate use, such as the area you just treated.
Repeat this process two more times to ensure all residual herbicide is removed from the tank, hoses, and nozzle. The rinse water, or rinsate, should never be poured down a drain, into the sewer system, or onto hard surfaces where it could contaminate waterways. Any small amount of unused mixed solution should be applied to a labeled area or given to a neighbor who can use it, as disposing of leftover solution often requires local household hazardous waste collection. Empty concentrate containers must also be triple-rinsed, with the rinsate added to the spray tank, before the container is disposed of according to local regulations.