This fact sheet provides information on the amount of specific fertilizers (based on percent nitrogen), to mix in one gallon of water, to provide a concentrated solution. This concentrated solution is then used with a fertilizer injector to deliver a a dilute amount of fertilizer.
Fertilizer proportioners or injectors are used in liquid feeding systems to eliminate the need for large volumes of stock solution tanks. They allow for the measured injection of highly concentrated fertilizer solutions. These devices "inject" a small quantity of concentrated fertilizer solution into the irrigation line so that the water leaving the hose (dilute solution) supplies the proper concentration of fertilizer. Most growers apply water-soluble fertilizers at a dilute concentration on a "constant feed" basis, with mostly every watering to insure an adequate supply of the essential elements for plant growth.
Rates of fertilization are often given in parts per million (ppm) of nitrogen (N), which is a way of expressing fertilizer concentration. One ppm is equivalent to 1 milligram/liter (mg/l). An injector setting of 1:100 indicates that 1 gallon of fertilizer concentrate delivers 100 gallons of final solution. This is not an indication that the injector is delivering 100 parts per million nitrogen.