1952

Center-Pivot Irrigation

Frank Zybach (1894–1980)

The standard way to efficiently irrigate an agricultural field is to lay horizontal pipe in parallel down the field, say at 40-foot intervals. Each horizontal pipe has vertical pipes, also at 40-foot intervals, and on top of each vertical pipe is a big sprinkler head. All of the pipes connect together back to a big pump that supplies the whole system with water.

This approach certainly works, but it is not very efficient. A square 9-acre (3.65 hectares) field takes something like 10,000 feet (3050 meters) of horizontal pipe and more than 200 sprinkler heads. Center-pivot irrigation was originally patented in 1952 by farmer Frank Zybach. In subsequent years, engineers perfected the original system to radically reduce the amount of pipe and the number of sprinkler heads needed to irrigate a field.

To get an idea of how this new system works, let’s imagine a 9-acre field is represented by a 700-foot (213 meter) diameter circle. At the center of the circle is the source of water from a pump. It connects into a riser and from there to a single horizontal pipe that is 350 feet (107 meters) long. The amount of pipe has been reduced by a factor of 30 in return for a longer irrigation time for the field.

The most ingenious part of this approach is the way that the horizontal pipe moves. The pipe is supported in the air by triangular towers on wheels. The towers are spaced every 100 feet, say, with one segment of pipe between each pair of towers. The wheels move very slowly via electric or water-powered motors.

Not only does this system save a lot of pipe, it also saves a lot of water. Sprinkler heads point straight down from the elevated horizontal pipe, reducing evaporation and wind loss.

By completely reconceptualizing the way they irrigate, engineers lowered cost and improved efficiency. The next time you fly over the midwestern states, look down and notice the impact of this reconceptualization. Further innovations like subsurface drip irrigation have proven even more useful in recent years.

SEE ALSO Green Revolution (1961), Drip Irrigation (1964).

An early morning view of a center-pivot sprinkler system in a farm field.