Closed-loop programs provide premixed herbicide in returnable, refillable containers, thus eliminating mixing, rinsing, and disposal by applicators. Photos: Dow AgroSciences LLC
Herbicide tanks should be routinely checked and maintained to avoid potential problems at the application site.

Municipalities that apply herbicides as part of their vegetation management activities can contract to receive premixed herbicides in returnable, refillable containers. These closed-loop container management programs are available from contract blending services that custom-mix and deliver herbicides in the required formulations and quantities.

Many public works and transportation departments implement integrated vegetation management programs that combine mechanical removal methods with herbicide applications to improve sightlines along roadsides, decrease erosion, and protect utility lines and rights of way. Procuring premixed herbicides via a closed-loop system offers several benefits:

  • Worker productivity. Applicators do not need to spend time mixing herbicides or triple-rinsing, storing, and disposing of empty containers. These functions take away from the time crews spend spraying. Participants in container management programs have found that using premixed herbicides almost doubles the number of acres workers can treat.
  • Worker safety. The closed-loop aspect of the transferring system reduces the potential for product spillage and worker exposure to chemicals because there is no mixing, triple-rinsing, or disposal of empty containers. By eliminating mixing in the field, container management also can prevent inadvertent mixing errors. Container management systems minimize unauthorized access to container contents since a special coupling system is required.
  • Environmental stewardship. The use of returnable, refillable containers cuts landfill waste, reduces liability for improper container disposal, and decreases chances of spills. This is particularly significant given a new EPA directive that imposes stricter rules on rinsing and recycling used containers. These factors also help reduce public scrutiny and improve public opinion.
  • Inventory management. Herbicide mixing contractors provide just-in-time shipments and prompt container retrieval. For users of these services, this eliminates container storage, reduces inventory costs, facilitates cash flow management, and minimizes theft and fire liability. Some contract mixing services enhance inventory management by using bar coding to track containers and herbicide usage. They provide reports to help users improve efficiencies, particularly when managing chemicals in multiple locations, by enabling functions such as assigning product to specific spray crews. Customers also have online access to tracking information.

    Public works departments that contract out herbicide application can benefit from selecting vegetation management professionals that participate in container management programs. Doing so supports responsible safety and environmental practices, which in turn can generate positive community perception. Because applicators are not opening and handling multiple herbicide containers in the field, the risk of herbicide spills is greatly reduced.

    The most common container sizes are 15 and 30 gallons, but containers can be larger than 300 gallons. These large containers of custom mixes can be shipped directly, which further reduces the number of containers for herbicide applicators to handle. When containers are empty, the containers are picked up or shipped back to the contract mixer, where the drums are inspected and cleaned in preparation for the next order.

    Returnable containers can also be incorporated with customer-owned poly tanks to reduce the risk or severity of accidental spills due to poly tank failure, says Fred Whitford, an extension specialist with Purdue University. Contents of returnable container totes can be mixed with water in a large poly tank. The containers can also be mounted alongside tanks on the truck so the applicator pulls herbicide concentrate from the tote and water from the tank at the same time. With such a setup, if the tank failed, then the spill would only be water. The structural integrity of the returnable container is monitored by the contracted mixing service.


    When purchasing tanks, an important factor to consider is the tank rating: 1.0, 1.5, or 1.9. Tanks rated 1.0 are designed to hold water, which weighs 8 pounds/gallon. “Vegetation management herbicides do not add significant weight and resulting pressure to poly tanks, but a potential spill due to tank failure makes it important to use a poly tank with a higher rating,” Whitford says. “Poly tanks used on vehicles should have the 1.9 rating because vehicle movement causes the liquid to slough back and forth, which puts more pressure on the tank.”

    Tanks with higher ratings cost more, but they provide a greater margin of safety. It is recommended to select tanks with the highest ratings whether they will be used for herbicides or water, and never to purchase used tanks.

    “The life span of poly tanks depends on a number of variables, including what they were designed for and how they are used,” Whitford says. “Some tanks are designed for stationary use, and some for transportation. Tanks that are stored inside have a longer service life than tanks used outside because, over time, sunlight will break down the ultraviolet protection used in the tanks. When that happens, the tank gets brittle and can fail.”

    Failure of poly tanks used with a herbicide tank mixture is the subject of a new Purdue Extension bulletin (“Poly Tanks for Farms and Businesses: Purdue Extension Service Bulletin PPP-77”). The bulletin suggests ways to evaluate tank condition. A water-based black marker can be applied to a small section of the tank and wiped off to see if cracks are visible in the poly. If so, the ultraviolet protection in the poly is breaking down and the tank should be replaced. A bright light also can be used to visually inspect the inside of the tank for cracks.

    — Bill Kline is a field scientist for Dow AgroSciences.

    Web Extra

    For tips on handling herbicides, click here.