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Irrigation
Afrikaans | Xhosa
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In South Africa, irrigation was practised for the first time at Jan van Riebeeck’s coming to the Cape.
Irrigation can be described as the artificial application of water to the soil by means of an irrigation system, with the purpose of providing plants with the water they require. That is, the correct quantity of water at the right time. Irrigation systems can basically be divided into three types, namely flood-irrigation systems, mobile irrigation systems and static irrigation systems. Let us consider the advantages and disadvantages of each of these separately. |
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Flood-irrigation systems are those systems by which water is flooded over a given surface of ground to water it. Examples are bed, furrow, basin and short-furrow irrigation systems. As indicated by the names, water is diverted into a bed, furrow or basin. The most important advantages are the low energy and capital costs, as well as the fact that the plant itself does not get wet, which reduces the occurrence of leaf and fruit diseases.
However, great water losses can occur if the system is not well designed and maintained. This system is also quite labour intensive. |
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Mobile systems include all systems that move while they apply water to the field surface. Examples of such systems are centre-pivot and travelling-gun spray systems. Although these systems have a low labour need, most of them are expensive. |
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Static systems include all systems that are immobile while water is being applied. Examples of these systems are sprinkler and micro-irrigation systems. |
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Sprinkler systems can be further divided into permanent and movable systems. With permanent systems, the pipes are left in the same position for the entire irrigation season. With movable systems, on the other hand, the pipes or sprayers, such as quick couple piping, draglines and canon sprayers, can be moved.
Although permanent systems are much more expensive than movable systems, the permanent systems are not as sensitive to wind as the movable ones are. Also, the moving of pipes of movable systems damages crops. |
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Micro-irrigation systems can be classified into drip and micro spray systems. These systems differ from sprinkler systems in that the water is regularly applied close to the plant roots in small quantities. Sprinkler systems, on the other hand, spread the water above the ground by means of sprinklers.
With micro-irrigation systems it is essential to install reliable filters to prevent the sprayers from becoming clogged. Although drip systems are not at all sensitive to wind, the good management of these systems is very important since only a part of the irrigation block is watered. The question now, is which system to choose. |
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The choice of an irrigation system for a specific case, is a difficult one because the various systems each have a wide field of application. Many factors play a role, for instance water quality, the type of soil to be irrigated, the slope of the land to be irrigated, the crop to be irrigated, the number of labourers that are available and, of course, the amount of money the farmer is able to spend.
Most important of all, however, is the farmer’s own personal considerations - which system can and do you want to use? You will agree with me that you need to consult an expert in the field of irrigation before you can purchase an irrigation system. |
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When you have decided on a system and bought it, its installation is very important. Underground pipelines must be laid at a sufficient depth for them not to be damaged by soil cultivation practices. It is also very important to lay the pipes according to the plans and specifications of the manufacturers. Drain-cocks must be out of the way and painted in a bright colour so that they will not be run over. It is also advisable to place permanent markers at suitable places on top of the ground to indicate the position of the underground pipeline. |
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The maintenance of an irrigation system is also important because it is designed to last for as long as the crop will be cultivated.
Some of the essential tasks to be carried out are:
The next logical question is: How do I know when and how much to irrigate? |
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The easiest way to determine this is to dig a hole in the land to determine the wetness of the soil. Sensors that measure the soil moisture are also available, but in this case I recommend you consult your local extension officer. |
FH Koegelenberg
ELSENBURG / Agricultural
engineering
