|Wall, R - UNIVERSITY OF IDAHO|
|Karsky, T - UNIVERSITY OF IDAHO|
Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 29, 2009
Publication Date: February 1, 2009
Citation: King, B.A., Wall, R.W., Karsky, T.F. 2009. Center-pivot irrigation system for independent site-specific management of water and chemical application. Applied Engineering in Agriculture. 25(2):187-198. Interpretive Summary: The application of chemicals through an irrigation system along with water is a common economical and effective practice in sprinkler irrigated crop production systems. The addition of a chemical application system independent of the normal water flow path on a center pivot irrigation system provides an opportunity to enhance system effectiveness, especially if the both water application and the chemical application systems are equipped for variable rate application. This would allow for independent site-specific water and chemical management to be based on site-specific crop requirements to increase water and chemical use efficiency. An independent chemical application system capable of variable rate application was installed and tested on a 4-span center pivot irrigation system equipped for variable rate water application. The chemical application system was assembled using mini-sprinklers and common commercial irrigation system components. Field testing demonstrated that the independent chemical application systems provided chemical application uniformity comparable or better than conventional application practice.
Technical Abstract: The development of lateral-move and center-pivot irrigation systems equipped for spatially variable water application and those equipped with an independent chemical application system have largely evolved independently. Integration of independent site-specific water and chemical application with lateral-move and center-pivot irrigation systems has received little attention. Increasing the utility of site-specific management technologies added to automated irrigation systems will increase their cost effectiveness and commercial potential. An independent chemical application system capable of variable rate application was installed and tested on a 4-span center pivot irrigation system equipped for variable rate water application. The chemical application system was assembled using mini-sprinklers and common commercial irrigation system components. For uniform chemical application, the coefficient of uniformity (CU) values ranged from 84 to 90 providing acceptable application uniformity. For variable rate chemical application, CU values ranged from 79 to 93 and measured mean area-weighted relative application values were well correlated with target relative application values with R squared of 0.9 or higher. Field testing of the chemical application system demonstrated that it can be used to effectively apply spatially variable chemical application concurrent and independent of spatially variable water application.