Drip irrigation is a relatively new type of irrigation system that reduces the amount of water used. In traditional agriculture, large quantities of water is supplied to the plants, most of which is lost to evaporation and not absorbed by plants. Water is supplied to a large basin or furrows which then spreads across the entire agricultural plot by way of gravity. This type of irrigation is the most common and has been practised in many parts of the world for thousands of years.
In recent years, sprinkler systems have gained popularity, they’re relatively easier to install and the irrigation is much more uniform. But drip irrigation brings a whole new level of sophistication to irrigation. As the name suggests, in drip irrigation, the idea is to provide water to the roots of plants in the form of drips. In this way the exact amount of water required for the plant is provided and wastage by evaporation is reduced.
How does drip irrigation work?
Drip irrigation collects water from a water source, treats it, passes it through a series of tubings and pipings until it goes through the emitters at which point the water is emitted at the roots of the plants. Water treatment depends on the water source. Impurities must be removed to avoid clogging.
Parts of a drip irrigation system
A typical drip irrigation systems consist of
- A water source
- Pumping system/station
- Filtration system
- Water meters
- Dosing system
- Distribution lines
The design of most other irrigation systems aren’t significantly affected by the water source, unless the water is severely contaminated or something. In case of drip irrigation, water source plays a huge role. Impurities in water can clog the drippers or emitters. Even chemical contaminants in water source can cause growth of bacteria or algae which can lead to clogging.
A pumping system or pumping station is necessary to maintain sufficient pressure throughout the system. Sometimes if the water source is at a very high level compared to the drippers or the if the water source is a municipal line, sufficient pressure may be available. But a low pressure will significantly affect the efficiency of the system,
As mentioned above, water quality is essential for the proper functioning of a drip irrigation system, and filtration systems play an important role in here. The filtration system must be capable of removing physical impurities like sand and clay, chemical contaminants, as well as organic matter. A water quality analysis is carried out before choosing the filtration systems and the systems could be media filters, disk filters, etc.
From the filtration system, the water goes to the distribution lines. But before that, a pressure gauge and a valve are installed. The pressure gauge is used to ensure proper pressure across the system. A difference in pressure can indicate a block or a clog. And most municipal codes dictate installing a backflow preventer to ensure that the water supply is not contaminated by – well you guessed it – water flowing back.
Water meters are essential not just to monitor your water consumption or to control the amount of water supplied. They’re essential to detect any blocks in the dripper systems. Some water meters record the total water consumption, while some indicate instantaneous water flow, which can be helpful for this.
While dosing systems are optional, applying fertilisers and pesticides through the drip irrigation system is highly efficient. Referred to as fertigation, such systems deliver fertiliser evenly across the entire field and improve fertilisation efficiency by up to 95%. And supplying pesticides the same way(referred to as chemigation) helps remove any organisms that may be growing within the drip system that can cause a blockage.
The pipe that carries water from the source is referred to as the mainline. These are then connected to sub main lines which connected to the dripper lines or lateral lines, or simply laterals. The lateral lines are laid along the rows of crops and have drippers or emitters attached to them. While choosing the distribution lines, it is important to ensure that they are rated to withstand the pressure demanded by the system. It is also important to make sure that pipes will not degrade or get damaged in the conditions in which they’re used.
Drippers deliver water to the roots of the crops. While designing a drip irrigation system, the spacing between the dripper lines and the spacing between drippers themselves are important. In a typical system, there could be hundreds or even thousands of drippers, and it is important that these drippers emit water at the same rate, the same amount of water, and that they’re resistant to clogging.
Drippers are mainly of two types: pressure compensated and non pressure compensated. The non-pressure compensated drippers deliver water at a rate determined by the working pressure of the system. The flow rate changes when the pressure changes. The pressure compensated drippers emit the same amount of water, maintain the same flow rate despite changes in the working pressure. They’ve got a diaphragm inside that adjusts to keep the flow rate constant dispute the pressure. The diaphragm also responds to clogs and flushes them out, so less maintenance is required for them.
Advantages of drip irrigation
- Highly efficient and precise, and therefore conserves water
- Unlike traditional irrigation, drip irrigation doesn’t cause runoff of soil nutrients
- By incorporating fertigation, up to 95% reduction in fertiliser usage is achieved.
- Soil erosion is reduced
- Non-uniform terrain or fields can be irrigated without any levelling
Disadvantages of drip irrigation
- The initial cost can be higher than other systems
- Clogging can cause problems
- Degradation of plastic lines used can reduce the life span of the system and affect the soil