Source: North Dakota State University
By Tom Peters, Extension Agronomist
I walked several fields last week that were damaged by herbicides that were tank contaminants from a previous job, in a previous field. It’s an awful feeling to see crop injury that is often sprayer load dependent and crop injury that changes for the worst from day-to-day. I know growers understand tank contamination as they inform me how many times they rinse the tank as we walk the field. My message today is very simple; it’s not about how much water you push through the equipment to clean residues, it’s about the detail, including identifying places where herbicide residues will collect in spray equipment.
My first recommendation is the most important – spray equipment should never be left to sit overnight without cleaning. Spray herbicide mixtures on fields and be sure to take time at the completion of the spray job to clean the sprayer, preventing drying and hardening of product residues. Flush the sprayer system with water if the same product mixture is to be used the next day. A more thorough cleaning is required if switching herbicides. At minimum, filling the sprayer with water and running water through the boom will prevent dried deposits from forming. I realize there are exceptions that may not be avoidable. However, mostly bad things happen when spray solution rides in the tank overnight.
Some herbicides are more difficult to clean than others. Some believe the liquid and dry flowable and water-dispersible granules are the most difficult to remove from spray equipment. However, herbicides formulated as solutions may also create challenges since they adhere to plastic tanks or hoses. For example, the growth regulator herbicides (2,4‐D, Clarity, Engenia, Stinger) and ALS‐inhibiting herbicides (FirstRate, Harmony, Matrix, Pursuit) attach to plastic tanks and rubber hoses and often are removed / cleaned by herbicides in subsequent loads. Glyphosate acts as a ‘tank-cleaner’s and removes herbicide residues from rubber hoses, strainers or screens that inadvertently causes herbicide damage in future loads.
Review the herbicide label for herbicide specific tank-cleanout procedures and recommended cleaning agents.
The following is a list of considerations one should make depending on spray equipment.
- Poly tanks require more attention when cleaning since herbicide residue can reside in hairline cracks and crevasses in the tank compared to stainless steel tanks. Use a power washer to clean the film that dries and adheres to sidewalls. Don’t forget about product that may solidify and accumulate in the sprayer sump.
- Make sure the sprayer is completely drained of any remaining product. Use the boom cleanout option if your machine is so equipped.
- Clean product line strainers and screens and inspect the inside of hoses, searching for cracks or where herbicide residue can accumulate residues.
- Clean irregular surfaces, such as baffles, plumbing fixtures and agitation units, areas where residues accumulate.
- Remove the end caps from the boom plumbing sections and flush with fresh water. These areas tend to trap products and cleaning them is essential.
- And of course, water is a good cleaner when used in combination with ammonia, tank-cleaner and/or other commercial products. However, water and tank-cleaners are not a replacement for the time and detail necessary to search for residues
There are some good on-line guides to use. For example, Removing Herbicide Residues from Agricultural Application Equipment, developed by Purdue University.