Center-Pivot Irrigation System for Independent Site-Specific Management of Water and Chemical Application

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 R2 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.