Herbicide application in western Canada is complex with many different factors that need to be considered. And with more diverse crop rotations, it is more important than ever to do a good job of sprayer tank cleanout.

Most herbicides used in western Canada have many great attributes, including good performance, concentrated formulations, tank mix options, and are easy and convenient to apply. With higher concentration comes higher risk of contamination on subsequent crops if spraying equipment, including tanks, filters, booms and nozzles, are not properly cleaned out.

Therefore, proper sprayer cleaning is a critical component of sprayer maintenance as it will reduce contamination risks and potential crop injury from equipment contamination.
Herbicide residue can stick to tank walls and crevices and may be brought into solution by a subsequent herbicide or a particularly effective spray adjuvant acting as a solvent. Plastic or polyethylene tanks and hoses tend to require more extensive cleaning than stainless steel tanks. Post-emergent application sprayed directly on crop foliage will have a greater potential for crop injury than soil-applied herbicides. Crop injury from sprayer contamination can occur even several months after using the sprayer without proper cleanup, and injury can occur even following several subsequent applications.

All herbicides have some risk of contamination if proper tank cleanout is not done. Many group 2 herbicides are considered higher risk due to high concentration of active ingredient in most formulations combined with very high activity on common western Canadian crops, especially canola.

What can growers do to ensure a successful tank cleanout?

1. Understand your risk. Different crops have different sensitivities depending on the herbicide used. If you are changing crops, the risk will be elevated. Concentrated group 2 products can cause injury even at very low use rates, so consider these factors and be prepared to spend extra time on tank cleanout if either of these apply to your situation. Keep good records for backup.
2. Know your sprayer. With many different manufacturers and models available, it pays to know where the problem areas might be, such as boom ends, elbows, valves, hoses, screens, and nozzle bodies. Ball valves or cam lever end caps are cheap insurance to make cleanout easier and keeping the operator’s manual with the sprayer is a good idea as well.
3. Empty the tank. Completely empty the spray tank thoroughly after use by spraying out the entire tank prior to clean out. Mix only the amount that is required – if a field is 200 acres, only add enough product to apply for 200 acres. Avoid leaving spray mixture in the tank overnight as some products become inactivated or the risk of contamination increases. Doing this will save money as well as cleanout time and will reduce risk of contamination of subsequent crops.
4. Do not wait to clean your sprayer. Clean out the spray tank as soon as possible after use. Dried pesticide residues are much more difficult to clean out than products in solution. Do this by thoroughly rinsing the spray tank with water, circulate the water through the sprayer system, and if possible, apply the rinsate to the treated field. Do not clean the sprayer near creeks, dugouts, sloughs, wells, or any other water source, and ensure that the wash water does not met any desirable vegetation or its roots. This includes crops but also trees, lawns and gardens commonly found in or near a farmyard.
5. Rinse #1: Spray down the inside of the spray tank with water and add water to the tank to fill to minimum of 10% of the tank volume, then agitate for 15 minutes. After agitation, flush out the sprayer through the filters, booms and nozzles, and open the ends of each boom and flush out the entire tank contents through the open booms.
6. Rinse #2: Fill the tank with water and add a tank cleaner such as All Clear® or 1% Ammonia at 1% v/v. Agitate for 5 minutes and flush the booms and nozzles again, then remove the nozzles and screens and clean thoroughly with detergent or tank cleaner before replacing. Pay particular attention to end boom caps as pesticides can settle in this area and become difficult to clean out. This is a critical step in the cleanout process, as some group 2 products can become trapped on tank walls when mixed with EC products and a tank cleaner is a must to properly clean the tank.
7. Rinse #3: Do a final rinse with water by filling the spray tank 1/10 full and agitate, then thoroughly flush out booms and re-install nozzles, screens and endcaps before resuming application.

If in doubt, always refer to the product label for full details, or contact AgraCity to discuss best practices for tank cleanout.

For further information on sprayers and application in general, go to www.sprayers101.com for great information about sprayers and application.

*Information for this article taken from the Alberta Crop Protection Guide 2019 and “Sprayer Tank Clean Out: Issues In the Field” presentation made by Keith Gabert of the Canola Council of Canada, Agronomy Update, Alberta, January 2016.