Sprinkler irrigation is a method of applying irrigation water similar to natural rainfall. Water is usually distributed through a system of pipes with a pump. It is then sprayed into the air through sprinklers so that it breaks up into small water droplets that fall to the ground. The pump supply system, sprinklers and operating conditions must be designed to ensure uniform application of water.
5.1.1 Suitable plants
Sprinkler irrigation is suitable for most row, field and tree crops and water can be applied above or below the crop canopy. However, large sprinklers are not recommended for watering delicate crops such as lettuce, as large water droplets created by sprinklers can damage the crop.
5.1.2 Appropriate slopes
Sprinkler irrigation can be adapted to any arable slope, whether uniform or wave. Lateral pipes supplying water to sprinklers should always be laid along a dry contour whenever possible. This will minimize pressure changes in the sprinklers and ensure uniform irrigation.
5.1.3 Suitable soils
Although sprinklers are adaptable to most soils, they are best suited for sandy soils with high infiltration rates. The average application rate (in mm/h) from sprinklers is always chosen less than the basic soil infiltration rate (see Appendix 2) to avoid surface ponding and runoff.
Sprinklers are not suitable for soils that crust easily. If sprinkler irrigation is the only method, then light fine sprays should be used. Larger sprinklers that produce larger water droplets should be avoided.
5.1.4 Suitable irrigation water
A good clean water supply, free of suspended sediment, is required to avoid problems with sprayer nozzle clogging and crop spoilage by sediment coating.
5.2 Scheme of sprinkler system
A typical sprinkler irrigation system consists of the following components:
Pumping unit
Trunk and sometimes sublines
The sides
Sprinklers
Figure 53 shows the main line in the foreground where the sprinklers and laterals are connected.
The pumping unit is usually a centrifugal pump that takes the water from the source and provides the necessary pressure to enter the piping system.