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Fluid Journal : Summer 2014
10 The Fluid Journal Summer 2014 Table 1: Sprinkler water losses and application efficiency for 1-inch water application. Water Loss Component Low-Angle Impact Sprinkler Water Loss Spray Head Water loss LEPA Water Loss Air Evaporation and Drift 0.03 in. 0.01 in. 0.00 in. Net Canopy Evaporation 0.08 in. 0.03 in. 0.00 in. Plant Interception 0.04 in. 0.04 in. 0.00 in. Evaporation From Soil Negligible Negligible 0.02 in. Total Water Loss 0.15 in. 0.08 in. 0.02 in. Application Efficiency 85% 92% 98% Figure 3. Map of the United States (excluding Alaska) showing cumulative grounwater depletion, 1900 through 2008, in 40 assessed aquifer systems or subareas. Index numbers are defined in table 1. Colors are hatched in the Dakota aquifer (area 39) where the aquifer overlaps with other aquifers having different values of depletion. Energy Precision Application (LEPA) system using bubblers located one foot above the ground. Both the water loss and application efficiencies given are based on a daytime irrigation of one inch applied to mature corn under no-wind conditions. Evaporation from the soil during irrigation is assumed to be negligible for the low angle impact sprinkler and spray head, a result of evaporation demands being met by the water evaporating from plant leaves. To realize the full potential of LEPA systems, growers must plant the crop in a pattern matching the irrigation track. Drop tubes must be placed at a height of 12 to 18 inches between every other crop row. Water must be discharged in the bubble mode or through socks to avoid wetting plant leaves. The surface storage must be created to prevent any runoff and maintain infiltration uniformity. On-farm efficiency is lower than that reported by research institutions. USDA/ARS publications suggest that efficiencies of 95 to 98 percent of the sprinkler water being available for crop use are attainable by growers. Drip irrigation Perhaps the most efficient method of irrigation is drip irrigation or subsurface drip irrigation (SDI). Drip irrigation delivers water through the use of pressurized polyethylene tubing, also known as drip line, and drippers that run close to the plants and can be placed either on the soil service or below ground. Generally, only the immediate root zone is wetted and the system allows precise application of water soluble fertilizers and other agricultural chemicals. Growers can achieve yield