How irrigation works

Drip Irrigation

There are four types of irrigation, surface irrigation, overhead irrigation, trickle or drip irrigation or sub-surface irrigation and plastic mulch. Each type is different in the way it allows water to reach the crops that require watering.

Surface irrigation is irrigation such as basin irrigation, border irrigation, furrow irrigation, and other forms of irrigation that use flooding. Surface irrigation is the simplest and easiest form of irrigation.

With this type of irrigation technique, fields are allowed to flood naturally, so this technique is totally dependent upon a suitable water source. This irrigation technique is best for fields used for grazing or recreation.

Basin irrigation, although more refined variation than surface irrigation, still relies heavily on plenty of water. Closely spaced crops with deep roots such as rice crops are particularly suited for this method. A bank or dike encloses these fields and holds the water on the field. The water for these fields can either be brought directly into the field using various channels and pipelines or manually.

With this irrigation technique, moving water to the channels where it floods the field causes a deep layer of mud to form at the bottom of the basin. Border irrigation, even though similar to basin irrigation, allows the water to drain from one end of the field to the other end without totally enclosing the field with dikes. This technique works best with sloping land as well as furrow irrigation.

More control of the water is determined with furrow irrigation by using channels in the field itself. Directing water along these channels allows the farmer to control the amount of water in different portions of the field surface by controlling the flow of water into each channel.

Overhead irrigation is very similar to an ordinary lawn sprinkler. This irrigation technique is very useful when covering a large area of land by pumping water in under pressure and sprayed down onto plants from flat spray nozzles mounted on an overhead network of aluminum pipes or even simply mounted on the top of a stake.

With this type of irrigation technique, it can be difficult to produce even coverage. More expensive systems are available that use a moving overhead boom. This mechanism moves across the length of the whole crop and can disperse the water in an evener manner. Another overhead technique is a water gun, which shoots water into the air and out over a field.

A large water gun can cover several acres of land without moving it. Overhead irrigation systems require a plentiful supply of water at relatively high pressure. These systems vary greatly in complexity and cost, depending on the acreage needing to be covered. Another downfall to this system is that the foliage of the crop will get wet which can lead to fungi and bacterial disease.

Trickle or drip irrigation is another technique that is used. This technique, which slowly provides water to a very specific area close to the roots of the plants by a network of drip emitters, allows the farmer more control than surface irrigation techniques.

Drip emitters are tiny nozzles laid along the ground to provide a slow and steady flow of water by linking them to an appropriate water supply. The advantages of using drip irrigation are precision and economics due to the amount of control that the farmer has. The flow of water provided by this type of irrigation is easily absorbed into the ground with little run off and waste.

Sub-surface irrigation, although initially expensive and not suitable for all areas can be an economical addition to drip irrigation. This technique requires irrigation tubing placed about 5 inches below the surface where the water gets where is it needed the most, at the roots of the plants. Reducing evaporation and no great opportunity for runoff are distinct advantages of this technique.

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