Fertilizer application methods
There are three main application methods for liquid fertilizers:
1. Direct soil application, mechanical spread by broadcasting or deep soil placement by injection.
2. Fertigation: Injecting the fertilizer solution with the irrigation water.
3. Foliar spray application
Principles of Fertigation
This is the most common method for the application of liquid fertilizer solutions and disolved solid water soluble fertilizers. The concentrated fertilizer solution is injected into the irrigation water, mixes with it and enters the soil during irrigation. This is the most efficient method for the fertilization of irrigated crops, specially for those irrigated with drippers, micro- jets and micro- sprinklers. A range of injection accessories is available for fertigation.
How to prepare a fertilizer solution from a solid, water soluble fertilizer
Gatit fertilizers should be dissolved in three volumes of water according to the following procedure.
For example: Fill some 50 liters of clean water into a 200 liter tank. Slowly add 50 kg fertilizer while stiring the solution and add water until you have 150 liter of completely dissolved fertilizer in your tank.
Don’t mix Gatit with other fertilizers, such as Calcium Nitrate without prior consultation. Mixing different fertilizers may cause a settling out, which may clog the irrigation system.
The By-pass fertilizer tank
This is the simplest and most widely used fertigation applicator. A measured amount of soluble or liquid fertilizer is introduced into the tank. The epoxy coated, pressure resistant, metal tank is connected to the main pipeline at two points: Pressurised irrigation water enters the tank at its bottom, and a diluted solution leaves through the exit at its top. A pressure- reducing valve separates both connections, creating a pressure differential between both connections. Some of the irrigation water is by-passed from the main pipeline into the tank containing the concentrated fertilizer solution. The fertilizer solution is diluted with the water entering the tank, and leaves by the exit. The concentration of fertilizer in the tank must be 0. At least five tank-volumes must flow through the tank. The The by-pass tank delivers the fertilizer from the tank as a “batch” to the irrigated field.
The Venturi injector
A Venturi injector is installed, or on the main pipeline, or on a by-pass. The Venturi consists of a conical reduction that increases flow velocity and creates a vacuum that suctions the fertilizer solution from an open container.
The venturi injector creates a loss of pressure in the irrigation system in the order of 30%. Therefore the by-pass installation requires a chocking valve on the main pipeline, or, alternatively, a booster pump that increase the pressure on the by-pass. A Venturi injector may be used both for “proportional” or “batch” injection of a measured volume of fertilizer solution into the irrigation system.
Fertilizer injection pumps
The fertilizer solution is injected into the irrigation system at a pressure that exceeds that of the system. Any kind of pump designed for this purpose may be employed. Fertilizer injection pumps allow injecting a constant concentration of fertilizer solution into the irrigation water (“proportional” injection). These pumps are classified according to the source of energy employed into the following three categories:
Energized by the water pressure of the irrigation system. The injector suctions the fertilizer solution from an open container and injects it at a pressure above that of the irrigation system. Used mostly in the open field where no alternative energy source is available. Allows for “batch” and “proportional” fertilizer application.
Pumps activated by a combustion motor
Fertilizer injection pumps connected to a combustion motor or the P.T.O. of a tractor. Commonly used for sporadic applications of fertilizers where high mobility is required at the field level. The pumps injection rate is easily adjusted by the user and suction the fertilizer from an open container.
Pumps energized by an electric motor
These pumps also inject the fertilizer solution from an open container into the irrigation system at high pressure. Since electricity is required for their operation they are commonly installed at the pumping station and the main control head. May be used for both “batch” and “propotional” fertilizer applications.
Important!! Suctioning the fertilizer from an open container implies that this system does not require a pressurised tank (as with the By-pass fertilizer tank). However the container should have a cover to prevent debris contaminating the fertilizer solution and maintain it clean.