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 the pivot is irrigated, often creating a circular pattern in crops when viewed from above (sometimes referred to as crop circles). Most center pivots were initially water-powered, and today most are propelled by electric motors. 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 the pivot is irrigated, often creating a circular pattern in crops when viewed from above (sometimes referred to as crop circles). Most center pivots were initially water-powered, and today most are propelled by electric motors. Center-pivot irrigation was invented in 1940 by 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 from Columbus, Nebraska. Trowbridge put up $25,000 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 six feet, 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 its subsidiary Valley Irrigation continuing his vision for irrigation in the United States, eventually spanning the globe. 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 in use, for example, in parts of the United States, Australia, New Zealand, and Brazil and also in desert areas such as the Sahara and the Middle East. Center pivots are typically less than 1600 feet (500 meters) in length (circle radius) with the most common size being the standard 1/4 mile (400 m) machine. A typical 1/4 mile radius crop circle covers about 125 acres of land Originally, most center 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. 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. When the angle is too large, the wheels rotate to keep the segments aligned.