|Garvey, Peter - PASS, INC.|
Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 1, 1997
Publication Date: N/A
Interpretive Summary: Applying pesticides by center pivot irrigation systems in irrigation water (chemigation) or by pivot attached sprayer systems (PASS) reduces pesticide application costs below what is needed with conventional application methods. However, many agrichemicals are not successfully applied by chemigation in a large volume of water by some irrigation systems. PASS constructed with conventional sprayer nozzles and sprayer components are costly and difficult to install. Therefore, low cost PASS were designed and installed on a single-tower and a four-tower center pivot irrigation system that uses micro-sprinklers and drip irrigation components to distribute agrichemicals along the pivot length. The low cost PASS has a coefficient of uniformity of 87 to 95 with sprinklers spaced 3 to 3.7 m (10 to 12 ft) apart and costs about 1/3 as much as PASS constructed with conventional sprayer components. The new design shows promise as a low cost PASS that uniformly applies a wide range of agrichemicals that will help bridge the gap between conventional sprayers and chemigation.
Technical Abstract: Center pivot attached sprayer systems (PASS) were designed and installed on a four-tower and a single-tower center pivot irrigation system. The PASS designs used micro-irrigation components and had a water application system with coefficient of uniformity (CU) values of 87 to 95. A computer model and an aircraft spray pattern sampling analysis system were effective methods for determining the water distribution uniformity of PASS. Sprinklers positioned 2 m (6 ft) above the ground had higher CU than when positioned 1 m (3 ft) above the ground. Plots of water distribution along the pivot length for variable and equal spaced sprinklers appeared to be different; however, their CU values were not different. Therefore, pivot towers that are connected and have the same traveling velocity can be designed with similar sprinkler flows and spacing without a loss in application uniformity. The micro-irrigation sprinkler and components were easy to assemble and low volume sprinklers provided good water application uniformity at a spacing of 3 to 3.7 m (10 to 12 ft).