Chemical Contamination in Agriculture (Part 2)

    From material absorption to backflow, chemical contamination in agricultural applications is a huge challenge, one that can cause thousands of dollars in damage to crops and rob time-strapped producers of their most valuable time. Hose + Coupling World is pleased to present Part Two of our interview Katelyn Duncan, a farmer and policy analyst, and Tom Wolf, Senior Scientist at Agrimetrix Research & Training, about the causes of chemical contamination and what producers can do to minimize risk. Read Part One here.

    By Jody Hewitt, Editor

    The trouble with expansion

    Expansion is another common issue with the hoses in their equipment, according to our experts. At the end of a sprayer pass, the flow will be shut off, closing an internal valve which cuts off the pressure in the boom.

    “You would think that all flow would stop immediately,” says Duncan, “but this is not always the case with some nozzles on some machines that do not have solenoid check valves”. The nozzle

    bodies themselves have a spring-operated check valve that will stop flow and prevent them from dripping when the pressure gets down to about 10 psi — but the typical operating pressure in a spray system is much higher than that and can increase to as much as 80 psi.”

    Because of this sudden burst in pressure, the sprayer hose balloons out, squeezing liquid out of the nozzle for another 5–10 seconds as it loses pressure and returns to its original dimension. Additionally, expansion can also cause hose fatigue and blow-outs.

    “One way to solve this would be to use a solenoid check valve on the nozzle,” says Wolf. “This valve actively shuts off the boom even if the pressure has not come down — instantaneous shut-off. It is not a cheap solution, though, and operators would benefit from a hose made of less expansive material.”

    A moment of inattention, a tank full of contamination

    After a sprayer is emptied in the field, it heads to the edge of the field for a refill. Nurse trucks, which are typically semi-trailers equipped with a water tank, make it possible for applicators to refill the sprayer tank with water via a 20–30-foot-long hose. This is a process that has boosted productivity immensely, but not without risk —specifically, the risk of backflow.

    “Let’s say you have a sprayer tank full of herbicides,” Wolf illustrates. “When you shut off the pump that pushes water into the tank, you must simultaneously shut off the valve. If you don’t shut it off exactly at the right time, the system could — simply by means of pressure — push the herbicide in the sprayer tank back into the feed.”

    While there are valves that can be used to prevent this, even a small oversight can cause a lot of damage, or at the very least, hassle. “This is really two issues,” says Duncan. “There is obviously the risk of contamination in the spray tank, but it is also a potential safety issue. The last thing we want is for the operator to come into contact with the chemical when it is preventable in the first place.”

    Closed transfer systems

    Inevitably, according to our experts, when you disconnect a coupling, especially during the filling process, you end up spilling up to a few liters of solution.

    In Europe, and in some jurisdictions across the United States — for example California — the industry is turning toward closed transfer systems for very hazardous materials. In these jurisdictions, the product is only legally allowed to be handled in a closed transfer system, one in which the chemical — likely in a jug — is connected via a dry coupling and metered into the sprayer directly. “When the jug disconnects,” says Wolf, “even if it is not empty, absolutely no material is present, and the operator is never exposed to a single drop of chemical. This is technology that is evolving within the industry right now.”

    Duncan adds that a closed transfer system for introducing pesticides is ideal, and how most chemicals are mixed on her farm via 450 litre totes or 108 litre drums of product. “It’s particularly helpful during the mixing process, when you’re mixing concentrated product, because that is where the greatest risk to the operator is. When there is water mixed into the solution, the chemical is diluted to a much lower concentration but when you are mixing in the chemical itself, there is the risk of unnecessary exposure to the concentrated product.”

    Would it benefit farm operators in Saskatchewan if the government were to adopt more stringent regulations?

    “In my experience,” responds Wolf, “regulations have never decreased over time, they have only increased. Perhaps because we are relatively remote, compared to other places in the world, we enjoy a bit more autonomy to decide on our own practices. I am very proud of the agricultural community in this region for its focus on proactivity when it comes to this — for example, using low-drift nozzles, not because it is the law, but because it is the right thing to do.

    Likewise, when it comes to safe disposal of waste products, we have to be proactive about following the right processes — processes that are safe and environmentally responsible — or risk being ‘found out’ and regulated, which could infringe on our ability to operate as an industry.”

    “As an industry, we need to handle pesticides responsibly and assume that consumers are always watching what we’re doing,” explains Duncan. “This means proper usage and disposal of products, along with educational efforts about the benefits of pesticides.”

    “I don’t want a carte blanche,” adds Wolf. “I want us to be legitimately safe, but I would rather that the community be in the driver’s seat.”

    Katelyn Duncan is a grain farmer, policy analyst, and blogger from Regina, Saskatchewan. You can find her blog page at

    Tom Wolf is a Senior Scientist, specializing in Spray Application Technology, at Agrimetrix Research & Training. You can access a library of his articles, videos, presentations, and ePubs on his website,