Thorough sprayer cleaning is necessary for all application equipment, going beyond a simple water rinse to prevent severe issues like crop damage and equipment degradation. Herbicide residue, even in minute concentrations, can cause phytotoxicity when the equipment is later used on sensitive plants or non-target crops. Residues accumulate in the plumbing system, screens, and tank walls. If not removed, they can be stripped out by surfactants in a subsequent spray mix, causing injury to the new crop. A complete decontamination process also safeguards the sprayer’s internal components from corrosion and prevents the environmental release of concentrated chemicals.
Essential Supplies and Safety Measures
Preparation for cleaning requires donning the appropriate Personal Protective Equipment (PPE) to protect against chemical exposure. Mandatory gear includes chemical-resistant gauntlet gloves and a chemical-resistant apron or coverall, such as a Tyvek suit, to prevent skin contact. Eye protection is also required; use chemical-splash goggles or a face shield, as pesticides are readily absorbed through the eyes.
The cleaning process must occur in an outdoor, well-ventilated space or on a designated impervious containment pad to manage spills and rinsate safely. Necessary supplies include a clean water source, calibrated measuring containers for accurate dilution, and basic hand tools for removing filters and nozzles. The specific cleaning agent varies based on the herbicide used, but general supplies include specialized commercial tank cleaners or a non-ionic detergent to emulsify oily residues.
Step-by-Step Sprayer Decontamination Process
The process begins by completely draining the remaining tank mixture through the boom onto a labeled, previously treated site until the system is empty. Immediately after draining, thoroughly rinse the tank interior with clean water, using 10 to 20% of the tank capacity. This first rinse dilutes the bulk of the remaining residue and should be circulated through the pump and boom for several minutes before being sprayed out.
Next, prepare the decontamination solution by adding the chosen cleaning agent to the tank, filling it to 10 to 20% of capacity. This solution must be circulated through the entire system, including bypass lines, for at least 15 minutes to reach all internal surfaces. For stubborn herbicides, allow the cleaning solution to stand in the charged system for an extended period, often eight to 24 hours, to penetrate dried deposits.
Physical cleaning of components that harbor residue is essential, as circulation alone is often insufficient. Filters, screens, and all nozzles, including tips and strainers, must be removed and manually scrubbed in a separate container of the cleaning solution. Once physical cleaning is complete, spray the entire cleaning solution out through the boom. Follow this with a final clean water rinse of the entire system to ensure that the cleaning chemicals themselves are removed, preventing potential damage to the next crop.
Specialized Cleaning for Stubborn Herbicide Classes
Certain herbicide classes require specific chemical agents to fully break down or solubilize their residues, as water and general detergents are ineffective.
Hormone-Type Herbicides (e.g., 2,4-D, Dicamba)
These herbicides are highly prone to absorption into the sprayer’s plastic and rubber components. They require specialized commercial tank cleaners or a household ammonia solution to neutralize and remove the residue. Ammonia is typically mixed at a rate of one gallon per 100 gallons of water. Failure to neutralize the residue allows it to be dissolved by surfactants in subsequent spray loads, leading to severe crop injury.
Sulfonylurea Herbicides
This class is known for its persistence and extreme phytotoxicity at very low concentrations. Cleaning protocols involve agents that increase solubility or promote decomposition. An ammonia solution elevates the pH of the rinsate, significantly increasing the water solubility of sulfonylurea residues, making them easier to flush out. Alternatively, a chlorine bleach solution enhances chemical decomposition, though it is less effective at dissolving residues trapped in crevices. Never mix chlorine bleach and ammonia, as their reaction produces toxic chlorine gas.
Oil-Soluble Formulations (e.g., Emulsifiable Concentrates)
These high-volume formulations require a detergent-based cleaner to effectively emulsify the oily carrier and strip the residue from the tank walls. They leave behind a difficult-to-remove film that requires a commercial tank cleaner formulated with strong surfactants. In some cases, an oil-based solvent may be used first to dissolve the oily residue, but this must be immediately followed by a detergent rinse to remove the solvent itself. Repeated applications of the cleaning solution are often necessary for full elimination.
How to Handle and Dispose of Rinsate
The liquid waste generated from the cleaning process, known as rinsate, contains diluted herbicide and cleaning agents and must be managed according to environmental regulations. Rinsate cannot be dumped on the ground or down a drain, as this violates the product label and risks contaminating groundwater or surface water. The most common method for handling rinsate is to apply it directly back to a site that is labeled for the herbicide that was just applied, ensuring the application rate does not exceed the maximum allowed for that site.
If the rinsate cannot be immediately reapplied, it must be collected and stored in an impervious containment area, such as a designated sump or load-out pad. In agricultural settings, this containment area allows the water to evaporate, concentrating the non-volatile chemical solids for later disposal. When rinsate volumes are large or the residue is particularly toxic, disposal must be arranged through a licensed hazardous waste management facility.