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Low Energy Precision Application (LEPA) Irrigation Method, a Forty-year Review

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2018 ASABE Annual International Meeting  1801598.(doi:10.13031/aim.201801598)
Authors:   James P. Bordovsky
Keywords:   Basin tillage, Chemigation, Evapotranspiration, Irrigation methods, LEPA, Low energy precision application, Runoff, Spray irrigation, Sprinkler irrigation, Uniformity, Water use efficiency.

Abstract. The low energy precision application (LEPA) irrigation concept was developed forty years ago (ca. 1978) to address the depletion of irrigation water from the Ogallala Aquifer and the sharp increase in energy needed for pumping in the Texas High Plains. The LEPA method applies water to the soil surface at low pressure as the tower / truss irrigation system moves through the field. This method brought changes in irrigation equipment and management that resulted in improvements in water productivity, particularly in semi-arid locations with diminishing water supplies. A review of published information pertaining to LEPA history, evaluation, and usage was performed. On landscapes of less than 1% slope, negative crop yield effects caused by irrigation runoff and start-stop system alignment was overcome with appropriately spaced basins, or furrow checks, and multiple irrigations over the course of the growing season. No consistent yield advantage at any level of irrigation was documented by placing water in every furrow (1-m spacing) compared to alternate furrows (2-m spacing). In irrigation treatments having <=50% of the full irrigation quantity, LEPA resulted in a 16% yield increase over sprinkler methods, although SDI resulted in 14% yield increase over LEPA. At irrigation levels > 50% full irrigation, crop yields of sprinkler treatments were only slightly less than those of LEPA, SDI were 7% greater than LEPA. The LEPA irrigation method was the catalyst for innovations in chemigation, no-till planting, and site-specific irrigation. As irrigation water becomes more limited, use and proper management of optimum irrigation methods will be critical.

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