Center-pivot irrigation

Center-pivot irrigation (sometimes called central pivot irrigation), also called water-wheel and circle irrigation, is a method of crop irrigation in which equipment rotates around a pivot and crops are watered with sprinklers. A circular area centered on a pivot is irrigated, often creating a circular pattern in crops when viewed from above (sometimes referred to as crop circles, not to be confused with those formed by circular flattening of a section of a crop in a field). Most center pivots were initially water-powered, however today most are propelled by electric motors.

Center-pivot irrigation systems are beneficial due to their ability to efficiently use water and optimize a farm's yield. The systems are highly effective on large land fields.

On March 23, 1914 James A. Norton of Odebolt, Iowa, filed the patent for the center pivot irrigation system. On August 17, 1915, it was granted as patent #1150144. The patent drawings shows multiple pairs of wheels supporting a pipe that is moved in a circle around a center pivot point. The description is: Watering arrangements making use of movable installations on wheels or the like movable around a pivot centre.

Center-pivot irrigation was invented in 1940 by the farmer Frank Zybach, who lived in Strasburg, Colorado. It is recognized as an effective method to improve water distribution to fields.

In 1952, Zybach went into business with A. E. Trowbridge, a friend, Ethan James Olson, from Columbus, Nebraska. Trowbridge put up $25,000 (equivalent to $296,000 in 2024) and got 49% of the patent rights. Zybach moved back from Colorado to Columbus, opened a shop, hired a few men, moved the height of the pipe up to 1.8 m (6 ft), and went into business. In the first two years of operation, they sold only 19 systems. The early designs were finicky and few farmers understood the systems. Zybach kept improving his designs and focused on making his machines better, rather than attempting to sell systems with problems.

Zybach saw success with modified designs, which improved the systems operational efficiency. In 1954, he licensed his patent to Robert Daugherty and his company, Valley Manufacturing. Daugherty's engineers spent the next decade refining Zybach's innovation, making it sturdier, taller, and more reliable, and converting it from a hydraulic power system to electric drive. Daugherty's company went on to grow into Valmont Industries, with Valley Irrigation being its subsidiary.

Center pivot irrigation is a form of overhead sprinkler irrigation consisting of several segments of pipe (usually galvanized steel or aluminum) with sprinklers positioned along their length, joined together and supported by trusses, and mounted on wheeled towers. The machine moves in a circular pattern and is fed with water from the pivot point at the center of the circle.

For a center pivot to be used, the terrain needs to be reasonably flat; but one major advantage of center pivots over alternative systems that use gravity flow is the ability to function in undulating country. This advantage has resulted in increased irrigated acreage and water use in some areas. The system is used in parts of the United States, Australia, New Zealand, Brazil, and in desert areas such as the Sahara and the Middle East.