Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2010
Publication Date: 11/22/2010
Citation: Evans, R.G., Iversen, W.M., Stevens, W.B., Jabro, J.D. 2010. Development of Combined Site-Specific MESA and LEPA Methods on a Linear Move Sprinkler Irrigation System. Applied Engineering in Agriculture. 26(5):883-895.
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 (Sidney) as it moved down the field. Water application depths were also varied for each crop (Nesson) depending on location as determined by a GPS system at the cart. 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. A total of four site-specific irrigation systems based on the same general controls and equipment designs were operational and being used in the spring of 2009 with a 5th to be added in 2010. However, the same controllers, valves and general software could easily be adapted to field scale, commercial self propelled center pivot irrigation systems. This project shows 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 the 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, total water use may be reduced, 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. Cropping systems that more efficiently utilize soil water have been shown to reduce costs and energy use as well as reduce water quality concerns. There is still ba need to develop more efficient methods of site-specifically applying crop amendments (e.g., nutrients, pesticides) through self-propelled sprinkler irrigation systems to reduce total amounts applied, improve profit margins and reduce adverse environmental impacts.
Technical Abstract: A site-specific controller, hardware and software systems were developed with the capability to switch between either mid-elevation spray application (MESA) or low energy precision application (LEPA) methods. These systems were field tested and used to manage site-specific irrigations under a linear move sprinkler system and simultaneously varied water application depths by plot as the machine traveled back and forth across the field. The controller and modifications to the water application methods utilized off-the-shelf components as much as possible. The linear move system was modified so that every plot could be irrigated using either MESA or LEPA methods. A programmable logic controller (PLC)-based control system was utilized to activate grouped networks of electric over air-activated control valves. Both the depth and method of irrigation were varied depending on the location of each plot in the field as provided by a low cost WAAS enabled GPS system mounted on the machine. When not being used, low-cost pneumatic cylinders lifted the LEPA heads above the MESA heads to avoid spray interference when the MESA were operating over a specified plot width and length. The control system was used on fifty-six 15 m ' 24.4 m (50 ft ' 80 ft) plots as well as several other adjacent research projects in which there were a mix of crops and a prescribed set of management experiments. While this particular application was designed specifically for a large, complex agronomic research project to address artificially imposed spatial variability water management, the same controllers, valves and general software could be easily adapted to field scale commercial irrigation. Keywords: precision irrigation, precision agriculture, spatial variability, variable rate irrigation, pneumatic controls, sugarbeet, barley, GPS