A growing practice in many areas of the country is the application of fertilizers through irrigation systems, often termed "chemigation". Although there are systems specifically designed for chemigation, in most cases an existing irrigation system is modified to mix the fertilizer with irrigation water. Fertilizers are generally stored in large tanks located near wells drawing ground water for irrigation. Fertilizers are pumped from the storage tanks into the irrigation water.
Concerns about ground water contamination from this practice arise from the fact that accidental backflow or siphoning of fertilizers into the well can occur when the irrigation pumping system shuts down unexpectedly. Unless the fertilizer user's equipment meets the following conditions set by the EPA, it will be in violation of FIFRA.
Rules For Chemigation Equipment
- The system must contain a functional check valve, vacuum relief valve, and low pressure drain appropriately located on the irrigation pipeline to prevent water source contamination from backflow.
- The fertilizer injection pipeline must contain a functional, automatic, quick-closing check valve to prevent the flow of fluid back toward the injection pump.
- The fertilizer injection pipeline must also contain a functional, normally closed solenoid-operated valve located on the intake side of the injection pipe and connected to the system interlock to prevent fluid from being withdrawn from the supply tank when the irrigation system is either automatically or manually shut down.
- The system must contain functional interlocking controls to automatically shut off the fertilizer injection pump when the water pump motor stops.
- The irrigation line or water pump must include a functional pressure switch, that will stop the water pump motor when the water pressure decreases to the point where fertilizer distribution is adversely affected.