An autonomous controller for site-specific management of fixed irrigation systems

Abstract

Distributed irrigation control (DIC) for site-specific management and/or operation of fixed irrigation systems is easier to install and maintain as compared to centralized irrigation control (CIC), but requires multiple controllers in the field. The advantages of DIC over CIC systems include: (1) reduced wiring and piping requirements, (2) a lower risk of complete system failure due to mechanical damage or lightening strikes, and (3) more flexibility when modifying or extending the system. In this study, a low cost solar-powered feedback controller for DIC of fixed irrigation systems was developed and tested. The specific tasks included the controller design (hardware and software), performance evaluation, and power optimization. The controller uses soil water potential (SWP) measurements to control the amount of water applied to each specific management area of a field, and measured system hydraulic pressure to communicate with other controllers. Each controller is autonomously powered by a solar panel and battery, eliminating hard-wire connections among control units. The results indicate that the controller was effective in maintaining the SWP in the root zone close to a predetermined management allowed deficit (MAD). The power supply was optimized using simulated and measured solar radiation data from two locations.