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Fluid Journal : Early Spring 2013
Table 2. Chemigation uniformity in a drip lateral (500 feet long) with 1-gph drip emitters installed at 5-foot intervals) for various injection times and post-injection clean water irrigations. The water and injected chemical travel time to reach the end of the drip lateral was 25 minutes. Injection time Post-injection irrigation Relative (min) time (min) uniformity (%) 50 50 100 50 25 98 25 25 95 25 50 90 13 25 81 50 0 25 25 0 11 13 0 7 results of some of these evaluations are shown in Table 2. The lateral line evaluated was a 500-foot drip lateral (16 mm polyethylene tubing) with 1-gph pressure-compensating drip emitters installed every 5 feet. It was determined through field evaluation that the travel time for water and injected chemicals passing through the lateral line was 25 minutes. Excellent chemical application uniformity was achieved when: • The injection period was equal to or greater than the water travel time to the end of the drip lateral (25 minutes in the test case) • The post-injection irrigation time was equal to or greater than the lateral line's water travel time. The results in Table 2 also show that there are two injection strategies to avoid. First, avoid injection periods that are less than the microirrigation system's water travel time to the end (hydraulically) of the system. Second, an injection should always be followed by a period of "clean" water irrigation. This post-injection irrigation should be at least as long as the water travel time to the end of the system. The worst chemigation uniformity results from too short of an injection period (less than the end-of-system travel time) followed by immediate microirrigation system shutdown. In fact, field measurements and laboratory studies have shown that clearing injected material from a microirrigation system takes even longer than it does to originally move the injected material through the system. Flow velocities at a pipe or tubing wall are very small (theoretically zero), so some of the injected material "hangs up" on the pipe or tubing walls and takes quite a while to clear from the system. Dr. Schwankl is an Irrigation Specialist with the University of California Cooperative Extension at the UC Kearney Agricultural Center in Parlier, California. The Fluid Fertilizer Foundation ACT NOW! JOIN IN THE SUPPORT OF THIS ORGANIZATION THAT DIRECTLY BENEFITS YOUR BUSINESS! The Fluid Fertilizer Foundation • 2805 Claflin Road, Suite 200, Manhattan, KS 66502 Write, call or e-mail the Fluid Fertilizer Foundation Phone: 785-776-0273 • E-mail: email@example.com Research and education for efficient use of fluids. We need you to join hundreds of other growers, dealers, fertilizer manufacturers and other supporting industries
Late Spring 2013