International Commission on Irrigation & Drainage Commission Interationale des Irrigation et du Drainage



Centre Pivot Irrigation

Centre pivot irrigation is a form of overhead sprinkler irrigation consisting of several segments of pipe (usually galvanized steel or aluminium) joined together and supported by trusses, mounted on wheeled towers with sprinklers positioned along its length.

 

The machine moves in a circular pattern and is fed with water from the pivot point at the centre of the circle. The outside set of wheels sets the master pace for the rotation (typically once every three days). The inner sets of wheels are mounted at hubs between two segments and use angle sensors to detect when the bend at the joint exceeds a certain threshold, and thus, the wheels should be rotated to keep the segments aligned.

 

Centre pivots are typically less than 1600 feet (500 meters) in length (circle radius) with the most common size being the standard ¼ mile (400 m) machine. To achieve uniform application, centre pivots require an even emitter flow rate across the radius of the machine. Since the outer-most spans (or towers) travel farther in a given time period than the innermost spans, nozzle sizes are smallest at the inner spans and increase with distance from the pivot point.

 

Originally, most centre pivots were water-powered. These were replaced by hydraulic systems and electric motor-driven systems. Most systems today are driven by an electric motor mounted at each tower.

 

For a centre pivot to be used the terrain needs to be reasonably flat; but one major advantage of centre pivots over alternative systems is the ability to function in undulating country. The system is in usein parts of the United StatesAustralia, New ZealandBrazil and also in desert areas such as the Sahara and the Middle East.

Centre pivot irrigation typically uses less water compared to many surface irrigation and furrow irrigation techniques.

 

Centre-pivot irrigation can reduce the amount of soil tillage that occurs and helps to reduce water runoff and soil erosion that can occur with ground irrigation.Less tillage encourages more organic materials and crop residue to decompose back into the soil, and reduces soil compaction.

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Dictionary - Centre Pivot Irrigation Terms

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