Submitted to: Encyclopedia of Water Science
Publication Type: Book / Chapter
Publication Acceptance Date: June 1, 2003
Publication Date: January 1, 2004
Citation: Kincaid, D.C., Buchleiter, G.W. 2004. Irrigation: site-specific. In: Howell, T.A., editor. Encyclopedia of Water Science. New York, NY: Marcel Dekker, Inc. p. 1-4. Interpretive Summary: Center pivot irrigation systems and traveling laterals are used on about 1/4 of the 50 million irrigated acres in the U. S. They provide an ideal platform for site specific (precision variable) irrigation of large areas with rolling topography, variable soil type, or other special water management needs. New technologies have made site-specific water application technically feasible. Many different scenarios of variable soils, different crops, limited water supplies and environmental concerns may make site-specific irrigation desirable. Because of the cost and complexity of these systems, economic feasibility will be highly case dependent.
Technical Abstract: Irrigation systems have evolved from flood systems to pressurized systems which enable one person to irrigate large areas with little labor. Center pivots are the most popular systems due to their ease of automation and control. Recent development of computerized controls, GPS guidance and mapping systems have extended the range of applicability of these systems. Water and chemical application can be tailored to smaller areas if and when it is desirable to do so. Reasons for site specific irrigation include avoiding watering of non-productive areas, tailoring fertilizer application to crop needs, and controlling timing and amount of water application on steep slopes and variable soil types. Application amounts under traveling laterals can be varied by using variable-flow sprinklers, or on-off valves on individual sprinklers or groups of sprinklers.