IRRIGATION MANAGEMENT USING AN EXPERT SYSTEM, SOIL WATER POTENTIALS, AND VEGETATIVE INDICES FOR SPATIAL APPLICATIONS

Variable-rate irrigation (VRI) systems are irrigation systems that are capable of applying different water depths both in the direction of travel and along the length of the irrigation system. However, when compared to traditional irrigation systems, VRI systems require a higher level of management. In this research, our objective was to evaluate and compare three irrigation management methods for their potential in managing VRI systems. The three irrigation management methods were the Irrigator Pro for Corn expert system, measured soil water potential (SWP), and remotely sensed crop vegetative indices (NDVI) to estimate crop coefficients. These irrigation treatments were implemented over six soil types under a VRI system for three years. Corn yields differed among years; average yields were 15.6 Mg ha(-1) in 2012, 10.5 Mg ha(-1) in 2013, and 13.5 Mg ha(-1) in 2014. However, corn yields for the three irrigation treatments were not significantly different for any one year. The mean yearly irrigation applied in 2012, 2013, and 2014 was 57, 7, and 156 mm, respectively. The mean water use efficiency (WUE) over the three years was significantly different, with values of 29.8, 16.8, and 23.8 kg grain ha(-1) mm(-1) for 2012, 2013, and 2014, respectively. For each individual year, the WUE among irrigation treatments was not significantly different. For the six soils types, there were no significant differences for corn yield or WUE. The Irrigator Pro for Corn and NDVI treatments managed irrigations as well as the traditional SWP-based treatment under the VRI system from 2012 to 2014. Each of these irrigation treatments was able to adequately manage irrigation spatially and produce adequate crop yields for the region. Each of these irrigation management treatments could be used effectively to manage irrigations under a VRI system with different management zones.