Introduction

Sprinkler irrigation in agriculture began with the development of impact sprinklers and lightweight steel pipe with quick couplers. In the 1950s, improved sprinklers, aluminium pipe, and more efficient pumping plants reduced the cost and labor requirements and increased the usefulness of sprinkler irrigation. In the 1960s, the development of moving systems, namely the center pivot, provided for moderate-cost, mechanical, high-frequency irrigation. Additional sprinkler innovations are continually being introduced that reduce labor, increase the efficiency of sprinkling, and adapt the method to a wider range of soils, topographies, and crops. Shortages of labor and water are resulting in more widespread use of mechanization and automation, including self- propelled sprinkler systems, automatic valves, and computer monitoring and control.

There are many types of sprinkler systems, but all have the following basic components:

• The pump draws water from the source, such as a reservoir, borehole, canal, or stream, and delivers it to the irrigation system at the required pressure. It is driven by an internal combustion engine or electric motor. If the water supply is pressurized, the pump may not be needed.

• The mainline is a pipe that delivers water from the pump to the laterals. In some cases the mainline is placed below ground and is permanent. In others, portable mainline laid on the surface can be moved from field to field. Buried mainlines usually are made of coated steel, asbestos-cement, or plastic. Portable pipes usually are made of lightweight aluminium alloy, galvanized steel or plastic. In large fields the mainline supplies one or more submains that deliver the water to the laterals.

• The lateral pipeline delivers water from the mainline to the sprinklers. It can be portable or permanent and may be made of materials similar to those of the mainline, but is usually smaller. In continuous-move systems, the lateral moves while irrigating.

• Sprinklers spray the water across the soil surface with the objective of uniform coverage.

Sprinklers irrigation systems can be divided broadly into set and continuous-move systems. In set systems, the sprinklers remain at a fixed position while irrigating; in continuous-move systems, the sprinklers operate while the lateral is moving in either a circular or a straight path. Set systems include solid set or permanent systems as well as periodic-move systems, which are moved between irrigations, such as hand-move and wheel-line laterals and hose-fed sprinklers. The principal continuous-move systems are center-pivot and linear-move laterals, and traveling raingun sprinklers.

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