principle to create a pressure difference between
the fertilizer container and the water supply line,
causing a flow of solution into the irrigation water.
The other system uses a positive displacement
pump, either water-powered or electrical, that
injects fertilizer solution into the irrigation water.
Each system can be adjusted to vary the ratio of
solution to irrigation water. There are a number of
manufacturers of each type of equipment. Figure
6–8 on the opposite page shows a typical pump type
installation.