Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
through the system. Injectors (chemical, fertilizer, or pesticides) and other automatic operating
equipment shall be located adjacent to the pump and power unit, placed in accordance with
manufacturer's recommendation and include integrated back flow prevention protection.
Fertigation/ nutrigation/ Chemigation shall be accomplished in the minimum length of time needed
to deliver the chemicals and flush the pipelines. Application amounts shall be limited to the
minimum amount necessary, as recommended by the chemical label.
Design Considerations: Fertigation is the application of fertilizer through an irrigation system.
Although used extensively in agriculture for decades, it has been less embraced in the landscape
irrigation industry. But today, the increase in environmental, legal, and maintenance cost concerns,
coupled with the demonstrated advantages for improved plant growth and health, make a
compelling case for fertigation. A properly designed fertigation system must consider all applicable
laws, plant material and fertilizer types, proper irrigation design, and the necessary
components/methods available, while weighing the cost/benefit concerns of the project.
Component/methods: The last major step is determining the injection method and materials of
the fertigation system. The preceding steps will have already determined some of the injection
systems requirements. In irrigation system, there are two primary means of injection. One is using
a venturi-type system. The other is a positive displacement, usually electrically driven, pump.
Advantages of the venturi system are its relative ease of operation, non-reliance on electrical
power, reliable operation, and accurate dosing. The disadvantages include smaller degree of
adjustability, larger pressure losses in the system, and susceptibility to clogging/flow restriction for
proper calibration and operation.
The advantages and disadvantages of the positive displacement pump are more or less
the opposite of the venturi system with one primary exception. If properly designed, installed, and
used, their accuracy can equal or even exceed that of the venturi system. The next consideration
involves material components. The selection of plastics, brass, stainless steel, etc. is determined
by the chemicals used, anticipated contact time, costs, and durability issues. Plastic components
are usually unaffected by most chemicals but are less durable than stainless steel. Stainless steel,
while probably the most durable of the three, is also the most expensive. Most components of the
average fertigation system will be made of plastic. Lastly is backflow prevention. While backflow is
a must when any potable water supply is used, it may also be required when using lakes and
wells.
The irrigation tank itself or separate tank may be used as fertigation system in the gravity
fed irrigation. The required concentration of nutrient solution are prepared in the tank and delivered
through the system network to the plant root zone. Some time, the suction line of the pumping unit
may also be utilized for the fertigation.
Fertilizer applicators: A number of different techniques are used to introduce the fertilizers into
the irrigation system Generally, fertilizers are injected into irrigation systems by three principal
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