1SPRINKLERS, CROP WATER USE, AND IRRIGATION TIME

Sprinkler irrigation has been an important part of Utahs agricultural production since the early 1950s. About 40 % of Utahs 1.3 million irrigated acres are watered with sprinklers, including hand move, wheel move, center pivot and other types. Sprinklers can be a good investment when properly designed, installed, maintained and managed. For every acre-foot of water supplied to an efficient sprinkler system a farmer can expect to harvest about 1 3/4 tons of alfalfa and 46 bushels of wheat. In contrast, the expected harvest with a typical surface irrigation system (flood or furrow) is less than 1 1/4 tons of alfalfa or about 30 bushels of wheat for each acre-foot of water applied. Sprinklers apply water more efficiently and uniformly than typical surface irrigation systems, thus they produce more yield for each acre-foot of water. Not all water applied by an irrigation system is used by the crop. Some water is lost to deep percolation, evaporation, or runoff. Application efficiency (Ea) is a term that tells how much of the water applied by the system is actually stored in the root zone for crop use. In Utah a typical sprinkler system has an Ea of 70 % which means that 70 % of the water applied by the sprinkler heads is actually stored in the soil for crop use. The actual Ea depends upon how evenly the sprinklers distribute water as well as other factors such as operating pressure, nozzle size an