Chemigation
Chemigation is the application of agricultural chemicals, such as pesticides, through an irrigation system. When the chemical is a fertilizer, the practice is usually called fertigation. Chemigation requires label approval and specific safety equipment to protect water supplies.
What is chemigation?
Chemigation uses an irrigation system as the application equipment. A chemical is injected into the irrigation water and delivered with it to the crop or soil. Center pivots and drip systems are the most common. Chemigation can save labor and trips across the field, and it can place a product exactly where irrigation water goes.
When the product is a fertilizer, the practice is called fertigation.
Requirements
- The label must allow it. A pesticide may be applied through irrigation only if its label includes chemigation directions.
- Safety equipment. Systems must be equipped to keep chemicals out of the water source, typically including check valves, vacuum relief valves, low-pressure drains, and interlocks that stop chemical injection if the irrigation pump stops.
- State rules. Many states require permits, inspections or applicator training for chemigation.
Why the safeguards matter
If an irrigation pump shuts down while an injection pump keeps running, chemicals can flow back into a well or surface water source, or be concentrated in the lines. The required equipment is designed to prevent that backflow and overdosing.
Practical considerations
- Irrigation must distribute water uniformly, or the chemical will be applied unevenly.
- Products must be compatible with the water and with anything else being injected.
- Application timing and water volume affect where the product ends up, on foliage or in the soil.
Frequently asked questions
Fertigation applies fertilizers through irrigation. Chemigation is the broader term and usually refers to pesticides and other chemicals, which carry additional label and safety requirements.
No. Only products whose labels specifically allow chemigation may be applied that way.
Sources
- Chemigation label requirements, U.S. Environmental Protection Agency
- Chemigation safety and certification, Land-grant university extension (e.g. University of Nebraska-Lincoln)