Chapter 20

Fertigation in Greenhouse Production

Fertilizer Dosing Methods

There are basically two ways to dose fertilizing nutrients to an irrigation system for vineyard production: (1) Dilute tank, batch method and (2) In-line injection, continuous method

Dilute Tank, Batch Method

he batch method of fertigation is a system in which the required amount of fertilizer is pre-mixed to the desired concentration (EC or ppm) in tank(s) before being distributed to the vineyard through the irrigation system. The irrigation water is diverted through the batch tank(s). The tank size should be large enough to contain the chemicals required for at least one fertigation operation. The size of the batch tank can vary from as small as 5 gallons to as large as 2,000 gallons. If more than one stock tank is in use, each tank should be clearly labeled as to the fertilizer it contains. Many batch systems (even manually operated ones) use two or more batch tanks to avoid chemical incompatibilities or to separate nutrients for flexibility.

In-Line Injection, Continuous Method

Most vineyard operations use in-line injection (i.e., injectors) for fertigation. Injectors take a small amount of concentrated chemical solution, such as water-soluble fertilizer dissolved in water in a stock tank, and introduce it into the irrigation line as a dilute solution at the proper concentration for delivery to plants. Injectors are also used to apply pesticides, plant growth regulators, wetting agents, disinfectants, and mineral acids during crop production. In-line injection is generally more popular than dilute tank systems since they do not require large holding tanks and they offer more flexibility. With in-line systems, concentrated stock solutions are continuously injected into the water stream as irrigation events are underway. Mixing usually occurs in the downstream section of the irrigation pipe or in a small mixing tank. Injection volumes are based on system flow rates, pH/EC sensor feedback, or a combination of the two.

In-Line Injection, Continuous Methods

The primary types of in-line injection methods for continuous fertigation are:

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