The injection of chemicals into irrigation systems is discussed in terms of injection systems, concentration injections, bulk injections, quantity of chemicals to be injected, injection system calibration, and injection periods. Sufficient clean-water flush time should be scheduled to purge irrigation lines of injected chemicals unless it is desired to leave that particular chemical in the irrigation system for maintenance purposes. Chemical injection rates vary with desired chemical concentration in the irrigation water, concentration of the stock solution, volume of chemical to be injected, and duration of each injection. All injection systems should be calibrated and maintained in proper working order. This information is presented to assist irrigation system designers and operators with chemigation system design, scheduling, and management.