Selecting an irrigation system for a site is not always straightforward and may depend on many factors. Sites may be suited to several methods of irrigation and the final selection is based on aspects such as water supply, soil, topography, climate, crop, labour availability, energy, initial costs, operating costs, adaptability to farming operations, adaptability for other uses, personal preference, reliability of the supplier and after-sales service. 

Whether you are setting up an irrigation system for the first time or considering changing your current irrigation system, there are a number of details to think about when choosing a system. 

Water 

The amount of available water, the quality of the water and its cost may influence the selection of an irrigation system. If the amount of available water is a limiting factor for the area to be irrigated, it might be more profitable to select a micro irrigation system, with high water use efficiency. Where irrigation contains harmful chemical substances that could burn the leaves of the plant or influence the quality of the product, overhead irrigation systems that wet the foliage should be avoided. 

Soil 

For micro irrigation of soils with a very high sand fraction, micro sprayers are preferable to drippers. However, if the soil has a very high clay fraction and low infiltration rate, a dragline system might be more suitable than a centre pivot. 

Topography 

Topography plays an important role where systems such as linear and flood irrigation are concerned and may dictate the choice of a system. 

Climate 

In very hot climatic conditions, water applied by sprinkler irrigation that wets the leaves of plants can burn the leaves. Under such conditions it would be better to use a micro system or a flood irrigation system. 

Energy costs 

Energy requirements, and therefore operating costs, of some systems such as the big gun, travelling gun and the highpressure travelling boom are considerably higher than for low-pressure systems such as drip irrigation, and should therefore be taken into consideration with system selection. 

Crop 

The crop to be irrigated will significantly influence the choice of an irrigation system. It would be ineffective to irrigate wheat with a drip system, which is only suitable for row crops. It would also be difficult to move the portable pipes of a quick coupling system in an orchid house. 

Labour 

A shortage of labour may force the farmer to use self-propelled or permanent systems rather than movable systems. 

Capital cost 

Micro irrigation systems are generally more expensive than portable systems, for example. The farmer may, for economic reasons, select the cheaper portable system, even though it might not be the ideal system for the application. 

Personal considerations 

Although each system has its own field of application, the final choice rests with the system user – the farmer. Each farmer has his or her own personal preferences that are influenced by various factors: whether the system is adaptable to his or her current farming practices, the level of training of labourers, whether the system can be adapted for other uses, and the reliability of the supplier, among others. 

The success or failure of an irrigation system depends to a large extent on careful selection, thorough planning, accurate design, and effective management Felix Reinders, Agricultural Research Council: Irrigation and Drainage Division 

For enquiries, send an email to Felix Reinders at reindersf@arc.agric.za.