Lepa irrigation developments

摘要

Advances in LEPA irrigation during the 1990's were primarily in equipment development, surface storage measurement, runoff control, and guidelines for LEPA irrigation of specific crops. LEPA application efficiencies in the 95 to 98 percent range areattainable when surface runoff and deep percolation are negligible. Uniformity coefficients along the irrigation system mainline can exceed 0.95 and, in the direction of travel, can exceed 0.80 with furrow dikes spaced about 2.0 m apart. Surface runoffhas the largest detrimental effect on LEPA application efficiency and uniformity. Without tillage to control runoff, runoff fractions exceeding 50 percent of the LEPA irrigation have been measured. The two primary methods for controlling runoff are basinand implanted reservoir tillage. With alternate furrow irrigation, they provide surface storage depths on a field basis of 25 mm or more and 12 mm or more, respectively. Bubblers and socks or sleeves have become the two most commonly used LEPA application devices. Bubblers are available in multi-function application devices that also include flat spray and chemigation modes. Single-ended and double-ended socks are usually attached to a spray application device for controlling the discharge rate. LEPA irrigation guidelines have been developed for corn, cotton, grain sorghum, wheat, and some minor crops. With full irrigation, crop yields and water use efficiencies are similar to those of other highly efficient irrigation methods such as spray and subsurface drip. With deficit irrigation, the runoff potential decreases, and LEPA tends to be more efficient than spray for drought tolerant row crops such as cotton and grain sorghum.