Tank Clean-Out
Sprayer tank clean‐out is necessary when changing between crops or between products to avoid crop injury due to contamination. A simple rinse or flush with water works for only a handful of herbicides, primarily glyphosate. The development of herbicide‐resistant weeds now requires the use of tank‐mix partners to attain proper weed control. As such, the addition of a tank‐cleaning agent is necessary to accomplish a thorough clean‐out.
When cleaning a sprayer, the primary concern is to attain three objectives:
- Diluting the active ingredient below damaging concentrations,
- Deactivating the herbicide or
- Removing the herbicide from the sprayer system.
Household ammonia, chlorine bleach, commercial tank cleaners and household detergents are examples of several types of tank‐cleaning agents. Each has a specific purpose or use. Commercial tank cleaners and detergents help remove water and oil‐soluble herbicides. Commercial tank cleaners usually perform better than household detergents; these tank cleaners generally raise the pH, which can deactivate some herbicides in addition to dissolving them. Chlorine bleach lowers the pH of the solution to enhance the degradation of some herbicides, while ammonia increases the pH of the solution to increase the solubility of others.
One note of CAUTION Never mix chlorine bleach with ammonia or chlorine bleach with fertilizers containing ammonia. It will produce a dangerous chlorine gas that irritates the eyes, nose, throat and lungs. Most herbicide labels contain information on sprayer clean‐out following application, as well as a recommended cleaning agent and cleaning procedure.
Taking time at the completion of the spray day to clean the sprayer can help prevent drying and hardening of product residues. This will also reduce the risk of corrosion and damage to sprayer equipment. A sprayer should never be left to sit overnight without cleaning. If the same product mixture is to be used the next day, flushing the sprayer system with water should be sufficient. However, if switching products or crops, a more thorough cleaning is needed. At a very minimum, filling the sprayer with water will prevent dried deposits from forming.
Generally, poly tanks tend to require additional attention when cleaning compared to stainless steel tanks. Pay particular attention to sprayer sumps and pumps, and clean or replace screens and strainers. Inspect the inside of hoses. Checked or cracked hoses can accumulate residues. Make sure to clean irregular surfaces, such as baffles, plumbing fixtures and agitation units. Don’t forget the inside top of the spray tank, as well as the tank cover.
Plant growth regulator herbicides (2,4‐D, Banvel®, Stinger®, etc.) and ALS‐inhibiting herbicides (Pursuit®, Maverick®, FirstRate®, etc.) are most likely to adhere to plastic tanks. Their chemical residues can subsequently be removed by herbicides and adjuvants used in future sprayer loads. One situation to avoid is a plant growth regulator mixture left in a sprayer overnight or for several days. If the next spray mixture has herbicides and adjuvants that act as tank cleaners, and are left in the tank for an extended period of time, the residues may be removed and mix with the current spray mixture. This may be a sufficient amount of residue to cause crop damage or crop loss to a sensitive crop.
When performing sprayer tank clean‐out, care should be taken to avoid contamination of crops, water supplies and streams. Clean in an area inaccessible to children, pets and livestock. The best disposal of rinsate is done by spraying back in the field according to labeled product rates.
Today, most of our herbicides and pesticides are crop specific. When going from one crop to the next, always check to see if your tank clean-out procedure requires more than one step.
In summary, the most important thing you can do for your crop’s health is to follow a proper tank clean-out procedure. Helena’s newest tank cleaner, WipeOut XS®, can help reduce the risk of contamination that can lead to crop damage by cleaning residue from spray tanks and equipment with twice the active ingredient power of conventional tank cleaners. Because the industry has more crop claims due to improper tank clean-out during the growing season, sprayer clean‐out and maintenance are essential for crop safety and should not be neglected.
- David Gehrts, Product Manager