Submitted to: Irrigation Business and Technology Magazine
Publication Type: Popular Publication
Publication Acceptance Date: February 19, 1997
Publication Date: N/A
Interpretive Summary: Guidelines for using the LEPA (Low Energy Precision Application) and spray sprinkler methods are not available for growers who irrigate grain crops for high-level yields in the Southern High Plains. In research tests, LEPA irrigation has higher application efficiencies than spray irrigation, but the use of LEPA may not always be justified because it requires higher cost tequipment and more intensive management. In two-year comparisons of LEPA and spray irrigation, grain yields of fully-irrigated corn, grain sorghum and wheat were essentially equal with the two sprinkler methods. The LEPA method was more efficient than the spray method for deficit-irrigation (used by growers with limited irrigation water) of grain sorghum, but for corn and wheat the deficit-irrigated yields with the two sprinkler methods were essentially equal. The higher costs and more intensive management of LEPA irrigation are not justified when irrigating corn, grain sorghum and wheat for maximum grain production. For specific applications, such as deficit irrigation of grain sorghum, the high application efficiencies of LEPA irrigation devices can be effectively utilized for irrigated grain production.
Technical Abstract: LEPA (Low Energy Precision Application) and spray sprinkler methods were used to irrigate corn, grain sorghum and wheat at both full and deficit irrigation levels in the Southern High Plains. Two LEPA methods, bubble and drag sock, and two spray methods, overhead spray and LESA (Low Elevation Spray Application) were used in the sprinkler methods comparison. .Full irrigation was defined as sufficient irrigation to maintain soil wate at a non-yield limiting level for all crops, and deficit irrigations ranged from zero to 75% of the fully-irrigated applications. All crops were irrigated with a lateral move irrigation system, and the row crops were planted on beds with diked furrows while the wheat was flat planted. Cultural practices, fertility amounts and pest control methods were typical of those used for a high-yield irrigated crop production in the area. With full irrigation, average two-year grain yields of all three crops were slightly larger with spray than with LEPA, but the differences were not statistically different. The LEPA and spray fully-irrigated, average yields were 7900 and 8150 lb./ac of grain sorghum, 209 and 221 bu/ac of corn and 67 and 72 bu/ac of wheat. Deficit LEPA irrigation was more efficient than spray irrigation for grain sorghum. For example, at the 50% irrigation amount two-year average grain sorghum yields were 7400 lb./ac with LEPA and 6400 lb./ac with spray. For corn and wheat, there was little difference in yields between the two sprinkler methods when using deficit irrigation.