Chapter 18

Fertigation Systems for Vineyards

Positive Displacement Pump Fertigation Injectors

ositive displacement pumps, such as piston and diaphragm pumps, are commonly used for fertigation and chemigation because they deliver a precise and consistent flow of chemicals into an irrigation system. These pumps are crucial for accurately applying fertilizers and other chemicals, ensuring that plants receive the correct nutrients and that the chemicals are evenly distributed with the irrigation water. Positive displacement pumps can be powered electrically, pneumatically, or hydraulically (water). Water-driven pumps can be installed in locations that lack power. Positive displacement injectors provide consistent injector ratios for their designed flow rates over wide variations in water pressure. Simple in design, the water enters one side of the unit, forcing up a piston. This action draws in the stock solution from a stock tank under the unit and into the chamber of water. The force of the water then pushes the piston back down, expelling the mixture of water and fertilizer out the other side, always in proportion to water flow. In most cases, the limiting factor with these injectors is the minimum and maximum water flow rates permissible.

Diaphragm Pumps

Diaphragm pumps are typically powered by electric motors but may also be belt-driven or powered by small gasoline engines. They have traditionally had the distinct advantage over piston pumps in that the flow rate is easy to adjust manually while the pump is operating. In addition, electric units can also be equipped with a VFD to control the speed of the pumping.

Piston Pumps

Piston pumps have the same characteristics as diaphragm pumps, in terms of power supply and maintenance. An advantage of piston pumps is that as positive displacement pumps, the discharge flow rate will not change as the irrigation pipeline pressure varies. Their big disadvantage is that flow rates cannot be adjusted while the pump is operating, unless a VFD is used. Therefore, one must measure the flow rate, shut the unit off, adjust the piston stroke, measure the flow rate, and repeat the process until the desired discharge is obtained.

Advantages/Disadvantages of Positive Displacement Pumps 

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