Components of a localized irrigation system (part I)
Drip irrigation, also called localized irrigation or irrigation drop by drop, is to supply water in the area surrounding the roots of plants. To do this, it is necessary to have an installation that adapts to different factors: land, type of soil, species to cultivate, climate and level of automation that the agricultural exploitation needs.
In response to these factors, the main components with which a drip irrigation facility should be counted are:
- Regulating reservoir
- Irrigation Head
- Irrigation Network
- Control elements
It allows to regulate the water supply to the holding, and to accumulate enough water to guarantee the necessities of the drip irrigation system. In the regulating reservoirs, the correct design of the inlet and outlet of water must be specially cared for, and its aeration to favour the precipitation of the iron compounds and sand.
The largest regulatory reservoirs are usually built to provide service to large cultivation areas, and are managed by the hydrographic confederations and supplied by the water of rivers, transfers or wells.
For calculating the total computation of the water needs of the farm, the evaporation losses, which vary between 6 and 10 of the volume spent in the irrigation campaign, the dimensions of the tank and the established irrigation shift, should be taken into account.
Its function is to control the entire irrigation system. It is located at the beginning of the installation, and includes all the equipment and materials used to control the irrigation system, measure the volume of water coming from the reservoir (counter), filter it, regulate its pressure, dose the fertilizers and program the Irrigation.
The following equipment is required:
It is in charge of supplying sufficient pressure and flow to the water to reach the emitters of the whole operation with the nutrients and programming envisaged.
There are several types of bombs, and your choice will depend on several factors.
1. According to the Power source used the watering pumps can be:
- Electropumps or centrifugal pumps: They use electric power, with a single-phase (230v) or three-phase electric motor (400v).
- Pump or combustion pumps: With combustion engines using liquid fuels such as petrol or diesel, if they are more powerful. They are used when the farm has no power supply or on small farms.
- Other types: Portable pumps, powered by a tractor engine, or solar-powered pumps.
2. Depending on the Suction height, which indicates the level at which the pump is installed above the mouth of the water intake piping, and are:
- Submersible Pumps: They are used when the suction height is high, and they are placed or on the surface of the reservoir using floats, or in an adjoining suction chamber following the principle of the communicating vessels.
- Non-Submersible pumps: Used when the suction height is low or the pump is located below the suction pipe. They are placed directly on the ground.
3. Depending on the position of the drive shaft, they are classified as:
- Horizontal Irrigation Pumps: They are the most frequent and allow to supply high flows and low pressures.
- Vertical Irrigation Pumps: They are used to provide high pressures.
The experts advise to install two pumps in parallel, which ensures the supply of irrigation to the farm, if one of them is damaged, something habitual in intensive exploitations.
Normally, the water that arrives at the regulating reservoir, presents impurities that we must treat before introducing it in our drip irrigation system to avoid problems such as the obstruction of the emitters. The solution is to use different water filtration systems and treatment to avoid or minimize these obstructions.
The contaminants that irrigation water can carry are organic, such as algae, fish, molluscs, insects, seeds, vegetable matter, worms, crustaceans,…, or inorganic, which are mainly silts, clays and sands, with sizes Very variable.
Another factor to consider is the degree of filtration of the device, which informs the filter’s ability to retain the polluting particles. It is measured in Mesh (number of holes in a linear inch) or in microns (size of the hole in the mesh and its degree of filtration). Its equivalences are as follows:
In localized irrigation, the filtration grade values vary from 130 to 80 micron (120 to 200 Mesh). That is, the size of the mesh hole is calculated to be less than 1/8 of the emitter’s maximum passing diameter.
The proper selection and placement of filter systems in different elements of the irrigation head will eliminate the majority of contaminants, avoid the appearance of obstructions and lengthen the life of the installation.
Types of filters
In a drip irrigation facility we can use different types of filters, adapted to the problem we want to treat:
- Hydrocyclone: It is not a filter as such, but a system to separate the sand or particles of higher water density. It is installed at the start of the irrigation head, to prevent the sand from damaging the pumps. It is specially used with the well water, because if the water has been reservoir previously it is not usually necessary.
- Sand Filter: It is the most effective filtering system to clean the reservoir water, and is used to remove organic impurities and small inorganic particles. Several battery filters are usually placed at the start of the irrigation head for optimal results and increase the life of the installation in the long term.
- Ring filters. They are suitable for water with little organic matter, are cheaper than sand and include a self-cleaning system that has made them very popular. The filtering effect is intermediate between mesh and sand filters. As a disadvantage, their water consumption is greater, and they allow to pass a certain amount of organic matter to the installation, which can cause short-term obturation problems.
- Mesh Filters: With its use it obtains a superficial particle retention, and is used to filter inorganic particles of not very dirty waters. They are usually installed in the irrigation head after the injection of fertilizers. They are not suitable for water with algae or organic matter, as they become clogged very quickly.
The correct choice and location of the filtering stations requires a prior knowledge of the polluting charge of the water, analyzing at the time when most irrigation is performed. In this way we can define the filtering capacity of the system to be installed.
Fertigation is to provide irrigation water with fertilizers and nutrients needed by plants, and is one of the actions that are carried out in the irrigation head.
After treating the water with the filters, the fertilizers and treatments located in the Fertilizing tanks are added, injecting directly to the water destined to the irrigation according to the programmed doses. These equipments also consist of agitators, which are used with less soluble fertilizers.