Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2011
Publication Date: 7/2/2012
Citation: Evans, R.G., Iversen, W.M., Kim, Y. 2012. Integrated decision support, sensor networks and adaptive control for wireless site-specific sprinkler irrigation. Applied Engineering in Agriculture. 28(3):377-387.
Interpretive Summary: A site-specific irrigation system has been designed, installed and successfully tested on a linear move sprinkler irrigation system. The PLC-based system has worked well for a 5-year period (2004-2008). The system successfully switches between MESA and LEPA irrigation methods as it moves down the field. This equipment greatly increased our research flexibility and allowed researchers to address multiple experiments under the same linear move system, greatly maximizing results and utility of these expensive machines. This is one of the first projects to successfully develop and field test a management program that integrates the specific irrigation system, wireless in-field sensor networks and decision support for site-specific sprinkler irrigation. This project illustrates it is possible to effectively install and operate precision site-specific irrigation systems on self-propelled linear move and center pivot systems. The knowledge of soil variability within a field is fundamental to the development of site-specific management areas since different soils have different water holding capacities. The ability to vary water application along the main lateral of the linear move based on position in the field allows researchers as well as producers to address specific soil, crop and/or special research conditions/treatments. By aligning irrigation water applications with variable water requirements in the field, it is assumed that total water use may be reduced thereby decreasing deep percolation and surface run off. Reducing excess water applications will decrease the potential to move nutrients past the plant root zone and fungal disease pressure should also decrease. Integration of the decision making process with the controls is a viable option for determining when and where to irrigate, and how much water to apply. Distributed in-field sensors offer a major advantage in supporting site-specific irrigation management that allows producers to maximize water productivity while enhancing net profitability. Site-specific irrigation decisions should be based on feedback of real time soil water and environmental conditions from distributed in-field sensor stations. Optimal use of available precipitation will obviously be required. The maximum benefits will be derived from a decision support system when soil water levels in selected areas of a field are monitored by some means to improve model simulation’s output and irrigation scheduling accuracy. Results of geo-referenced grid sampling of soils, yield maps and other precision agriculture technologies can also be major components of these management systems. Monitoring systems can be field-based measurements or remotely sensed or an integrated mix of both types. Remote, real-time monitoring and/or control of important farming operations that add value through improved efficiency and efficacy of targeted, site-specific management practices (precision agriculture) are now available, but are not generally being applied for a number of reasons. This is particularly true for self-propelled, site-specific sprinkler irrigation systems, which is primarily due to a lack of scientifically demonstrated benefits in terms of water and production cost savings by researchers and industry. There is little question that site-specific sprinkler irrigation systems like the one described in this paper are wonderful research tools. However, almost all of the research done to date has been directed towards development and improvement of hardware and control software. Little research has been done on the management of these systems for greatest agronomic benefit, and that has been directed towards meeting full crop ET and maximizing yields per unit area. Existing decision support systems are simplistic and directed towards maximizing yield per unit area. However, decision support programs need to move to
Technical Abstract: The development of site-specific sprinkler irrigation water management systems will be a major factor in future efforts to improve the various efficiencies of water-use and to support a sustainable irrigated environment. The challenge is to develop fully integrated management systems with supporting elements that accurately and inexpensively sense within-field variability and then optimally control variable-rate water application systems in ways that account for the spatial variability affecting water use. Recent advances in sensor and wireless radio frequency (RF) technologies have enabled the development of distributed in-field sensor-based irrigation systems to support site-specific irrigation management. Thus, integration of a decision making process with a distributed wireless sensor network (WSN) and providing real time input to site-specific controls is a viable option. This presentation reviews research on the implementation of an in-field micrometeorological information that was fed from the distributed WSN and displayed on a geo-referenced field map in a computer base station. Low-cost Bluetooth wireless RF communications from both a distributed WSN and the machine controls monitoring of sprinkler status and GPS location were interfaced with a computer base station for processing by a decision support program, which updated the instructions to the variable rate irrigation controller for real-time site-specific control. The decision support was optimized to adapt changes of crop design, irrigation pattern, and field location for instructions for individual sprinkler heads on how much water to apply and where. A graphical user interface (GUI) with a simple click-and-play menu was used, which also allowed growers to remotely access field conditions and irrigation status at the home or office via the wireless RF communications. This is one of the first projects to develop and field test an integrated management program for site-specific sprinkler irrigation. Keywords. Decision support, adaptive control systems, irrigation controls, sprinkler irrigation, wireless networks, sensors, automation, water management, measurement