Certain jobs on the farm aren’t anybody’s favourites. Repairing a planter in the middle of a soybean field in early June is right up there on that list, and so is picking stones on just about any day. And up there with them is cleaning out the sprayer, which is another of the chores about which no one ever said puts the joy in farming.
The somewhat official line on cleanouts is that they should be performed at the end of a day’s application, and definitely when changing from one treatment to another. But a conventional triple rinse procedure takes anywhere from 20 to 45 minutes (according to an informal survey of Ontario growers) and even under good conditions, there are often gallons of spray mix left in the lines, pump and tank sump.
Left undiluted, the residues can dry on or soak into sprayer parts, and they have the potential to lift and cause crop injury during subsequent application, or to build up until the sprayer is thoroughly cleaned.
Now there’s a system which can perform the task in roughly one-third of the time. At the 2017 edition of Canada’s Outdoor Farm Show, Dr. Jason Deveau and Mike Cowbrough, both specialists with the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), hosted daily demonstrations of a new continuous-rinse system.
The demonstrations included a short tour through plots exhibiting crop injury to small amounts of dicamba, just to show the damage these can cause.
This continuous-rinse design was first constructed and pressed into service in Europe, where pressure has been increasing in countries that take water from ground sources. Since 2006, farmers in France and Belgium have been legislated to perform tank cleanouts, not just at the end of the day, but BEFORE leaving a field.
In fact, the regulations stipulate they can’t leave the field until their spray is down to one to two per cent of the original tank concentration as sampled at the nozzle.
The legislation came after testing revealed unacceptable levels of farm chemicals in drinking water samples in those two countries. Point source contamination occurred from tank fills and cleanouts performed repeatedly in the same spots. The surface run-off leeched chemicals into the water supply.
According to Deveau, other European countries are now discussing similar regulations.
Pump more, or more pumps?
The problem was forcing farmers to take 20 to 45 minutes to rinse the sprayer after every field. European engineers knew that the sprayer’s pump was employed for two different tasks, which could not occur simultaneously: spray from the boom or draw water from the clean water tank.
This is why the triple-rinse method is a tedious back-and-forth dance of drawing clean water into the product tank, then circulating, then spraying out the rinsate. But beyond the time and manual effort required to change valves, the real problem is that there can be five to 15 gallons of spray mix left in the sprayer when “empty.”
“If you introduce one-third of the clean water you’re carrying using the main pump through the rinse-down nozzle, it dilutes the remaining five to 15 gallons and you get slightly less dirty water,” says Deveau, the spray specialist with OMAFRA. “Then you circulate that through the system as best you can, climb back into the cab and spray it out the boom. But again, you’ve left five to 15 gallons of now more-dilute solution behind.”
That step is repeated two more times with the remaining solution becoming more dilute each time. This reality of adding clean water to dirty is also why a single, high-volume flush is not as effective as multiple, lower-volume serial dilutions, but they take a great deal of time, dissuading some operators from the practice.
What if it could be faster?
To help, European engineers added a dedicated low-volume pump for the clean water, creating the continuous-rinse system.
“When the product tank is empty, the operator flips a switch in the cab to start the clean-water pump. It draws from the clean-water tank, rinsing the product tank via the wash-down nozzles from the tank,” says Deveau. “The main pump is free to continually spray while rinsing is happening. This means clean water displaces the dirty water rather than dilutes it. Best of all, you never leave the cab, so operator exposure is nil, and you’ve sprayed that rinsate out over the field where it can break down naturally rather than dumping it in a single location.”
According to Deveau, continuous rinsing is not exactly a new concept. There are still farmers who remember their fathers parking the sprayer, plumbing a water supply hose into the suction line while spraying out the rinsate. However, the sprayer is stationary and the rinsate accumulates in that single location.
During formal testing in the late 1990s, results indicated that continuous cleaning was more efficient than triple rinsing. In Deveau’s and Cowbrough’s demonstrations, continuous rinsing is “as good as” the triple- or quadruple-rinse procedures.
Last year, OMAFRA worked with HJV Equipment to adapt the system to a Rogator, and then worked with Green Lea Fertilizer and Application Equipment to instal a similar design on a Case IH Patriot 4440 for about $3,000 (not including labour). That may sound expensive, but in view of the time savings, the reduction in residue within the sprayer and the subsequent reduced potential for accidentally carrying over sprays into a sensitive crop the team says it pays for itself fairly quickly.
Even without the return on investment, it’s worth considering just for the environmental stewardship benefits alone.
Direct to the lines and boom
There is another modification that Deveau and others are exploring, which would allow the operator to shunt clean water directly from the rinse tank to the lines and boom. Such a configuration already exists as an option on some sprayers, yet it can be added cost-efficiently to a continuous rinse system and initiated from the cab.
“Consider a scenario where the operator is rained out, or perhaps has too much spray mix,” says Deveau. “Their intention is to return later to finish, but they don’t want product to sit in the lines and nozzles where residue can form. So they elect to rinse out the lines and boom using the rinse pump, bypassing the product tank and product pump. It’s a nifty little perk requiring only one more electric solenoid valve, a switch and an additional ‘T’ in the plumbing.”
A couple of other clarifications are helpful. Although the plot demonstrations exhibited low-level crop injury in soybeans, this continuous rinse system is not exclusive to dicamba formulations. Any spray application will benefit from a system like this. Deveau emphasizes that the Outdoor Farm Show represented a very stringent metric to demonstrate that both rinsing protocols are equally effective, but that no rinsing method is as effective as a full sprayer decontamination. That process requires the use of a detergent and soaking time to address all dead-end plumbing issues.
It’s also interesting to note that Monsanto and Syngenta are two companies that are interested in researching a continuous rinse system.
In the field plots – seeing is believing
During the Outdoor Farm Show demonstrations, Cowbrough shared his observations and insights from the plots that provided a visual indication of soybean sensitivity to dicamba.
According to Cowbrough, he had two goals with the demonstration: to see if the continuous rinse process was equivalent to the triple-rinse process (in terms of spray cleanout), and to illustrate how sensitive soybeans are to dicamba.
“We thought the best way to quantify the equivalence between continuous and triple rinse was to spray the rinsate collected over top of a sensitive crop, make visual injury ratings, and take yield,” says Cowbrough. “We have completed harvest at two sites and soybean yield was equivalent using both methods, once you got to the final rinses (third or fourth rinse compared to 75 and 100 per cent water run through using the continuous rinse system).”
In testing for sensitivity in soybeans, Cowbrough refers to the body of research on the topic that shows the impact varies based on application timing, with exposure during the vegetative stage having less impact than at the reproductive stage.
One research paper cited a 10 per cent yield loss in soybean at 0.16 per cent of the labelled rate of dicamba, so the cupping symptoms do show up at lower doses.
“All of this is to say that if one does not do a thorough decontamination of a sprayer — clean the filters, end caps — with certain herbicides like dicamba, there will be issues,” says Cowbrough. “This was also meant to demonstrate that the continuous rinse system cannot replace a thorough decontamination or cleanout procedure, since we collected enough dicamba in the filters after each method of rinsing.”
It’s a quick, efficient method to routinely rinse out the majority of the sprayers so that the decontamination process is easier and more efficient.
Again, Cowbrough’s and Deveau’s comments and the demonstrations they hosted were not an indication of dangers that are unique to dicamba. They apply to all chemistries, even though the crop damage in the soybeans from the dicamba rinsate was rather obvious.
For more information, check “Installing a Continuous Rinse System” and “Continuous rinsing should be considered in North America” on the Sprayers 101 website.
“Even for myself, I knew dicamba was potent,” says Cowbrough. “But it wasn’t until I started to go through the literature and see the cupping from what we collected from the sprayer… the rinsate coming out of the sprayer was looking clean and was odour free, yet we still saw cupping. And that was after four serial rinses.
This article was originally published in the January 2018 issue of the Corn Guide.