label specifically states that the product can be applied by the type of irrigation system to be used, the pest to be controlled, and the crop to which it is being applied. Chemigation may therefore be limited in countries where registration for the specific use has not been attained.

• Some chemicals are corrosive to the irrigation equipment.

• Additional components such as injectors, tanks and safety devices are required.

• Chemigation requires a change in management techniques. Operator training is required to ensure that the operator is careful and attentive and understands backflow prevention equipment, injector calibration and the operation of the irrigation system.

• Chemigation cannot be used when soil moisture is already near field capacity and irrigation is not needed.

Laws & Regulations There are many local, municipal, state, provincial and federal laws, regulations and codes that pertain to the use, handling and application of chemicals through an irrigation system. The laws and regulations seek to ensure that the chemical is used for the intended purpose and that proper steps are taken to protect the environment. Local governments often have plumbing codes or other regulations that specify backflow prevention requirements to protect against backsiphonage or backpressure of the chemical into groundwater, surface water or other drinking water supplies.

The rules regarding pesticides are intended to protect workers from exposure; contain the chemical to the target site or pest; avoid uncontrolled or accidental entry of the chemical into the environment, especially drinking water supplies; and ensure that the crops produced are safe for the intended use or human consumption.

Worker protection is addressed by regulations specifying personal protective equipment and safety equipment on the injection system and by restricting entry of workers into the field after chemigation has been completed. In some jurisdictions, certification is required for the application of pesticides through an irrigation system. Field posting is often required to inform the public that the water from the irrigation system is not potable and field entry is not permitted.

For pesticides, the product label is the law, and label application rules must be followed. The label specifies (a) the type of irrigation system that the product can be applied with, (b) the type of injection system to be used, (c) required injection system safety features (e.g., interlocks with the pump), (d) automatic system shutdown precautions should pressures drop to the point where product distribution is adversely affected, and (e) the pest to be controlled and the crop on which the pesticide can be used.

Rules governing fertigation are generally intended to protect the environment and drinking water supplies. There is more flexibility with the type of injector that can legally be used, but similar backflow prevention equipment and other safety equipment such as interlocks with controllers and pumps are still very necessary to protect from backflow risks into the connected irrigation water source.

Robert G. Evans, PhD, is a retired research

leader from the United States Department of Agriculture’s Agricultural Research Service’s Northern Plains Agricultural Research Laboratory in Sidney, Montana.

Ted van der Gulik, CLIA, is the director and president of the Partnership for Water Sustainability in British

Columbia, Canada. In February 2014, he retired from the Ministry of Agriculture after 35 years of service

as the Senior Engineer in the Sustainable Agriculture Management Branch in Abbotsford, Canada. van der Gulik was awarded the Irrigation Association’s Crawford Reid Memorial Award in 2000.

For more information on chemigation and fertigation, see Irrigation, Sixth Edition, the most comprehensive reference book ever published on the evolution of irrigation systems and the many facets of irrigation systems, technologies and practices. Irrigation, Sixth Edition is available atwww.irrigation. org/store. 17

Irrigation Sixth Edition

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