Center pivot systems irrigate large surfaces in a circular manner. They are used in places where water is a strongly limiting factor. Also in fields where it is desired to increase irrigation efficiency, making better use of water and greatly increasing crop yields. The efficiency in pivot irrigation is 85% to 90%.
It is a system that adapts to the undulations of the terrain (this does not need to be flat). Depending on the manufacturer and design of the equipment, they can be used on terrain with up to 30% slope.
The distribution of water throughout the structure is carried out by the manufacturer by selecting the size and spacing of the sprinklers. Sprinklers located near the center of the pivot need to deliver less water than those located toward the end. With new technologies in pivot sprinklers, manufacturers have managed to lower the operating pressure of the sprinklers even further (up to 6-10 psi =0.42-0.7 bar); and with it, the operating pressure of the pivots (and energy consumption).
The largest proportion of the global pivot irrigation market is electrically driven, as there are various manufacturers (Irrifrance, Chamsa, RKD, Valley, Pierce, Rokking, Reinke, Bauer, Ice Innova (Irrigation Components Europe)).
Electrically driven pivots stop their motors hundreds of times each day. The speed of the electric motors is fixed and each of the pivot towers describes a different circumference. For the pivot to move as a whole, the towers that are most advanced must stop and wait for them to be reached by the other towers, and then they are put into operation again.
The hydraulically driven pivots automatically regulate the speed for each of its towers, so they are all moving simultaneously, and at the required speed. As all the towers move constantly, irrigation uniformity is greater.
There are no differences in energy consumption between an electrically driven pivot and a hydraulic one. The sum of the size of the electric motors on the electric drive pivot equals the size of the motor that drives the hydraulic pump on the hydraulic drive pivot. Where there is an electric pivot, this can be replaced with a hydraulic pivot without the need to change the wiring that supplies energy to the pivot.
Electrically driven pivots are more complex. They have control boxes in each of the towers that operate the electric motors. Maintenance is carried out by an electrician with knowledge in the area.
Hydraulically powered pivots have a central hydraulic pump and hydraulic motors on each of their towers (similar to how heavy earth-moving machinery operates). They are simple to operate and maintain.
Crops that are generally irrigated with center pivot systems are corn, soybeans, wheat, cotton, peanuts, potatoes, sunflowers, alfalfa, sorghum, sugar beets, vegetables, natural pastures, etc.
There are also center pivot installations where sprinklers have been replaced with drip lines, allowing drip irrigation of some crops, but at a lower installation cost.
Corrosion causes electrical pivots and their complex drive systems to malfunction after a while. This is accentuated when fertigation is carried out (for example with urea and phosphoric acid).
The pivots can be operated by simple boards or even by complex computerized systems with communication via telephone or radio. In this case, the pivot can for example be put into operation depending on the soil moisture or the weather conditions.