|Ayars, James - Jim|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 11/11/2002
Publication Date: 10/1/2006
Citation: Ayars, J.E., Phene, C.J. 2006. Automation. Book Chapter. Chapter 7 Microirrigation for Crop Production, pgs 259-284. Interpretive Summary: Microirrigation systems have the potential to significantly improve irrigation efficiency, crop yields, and reduce the impact of irrigation on the environment. However, this potential will not be realized unless the system is automated. Automation will allow water to be applied when and in what quantities needed to maximize yield with minimum impacts on the environment. Since microirrigation systems are pressurized, water will be delivered throughout the field and there is potential for high uniformity of application and low values of deep percolation losses. Additionally fertilizers can be applied to spoon feed the crop. The automation system is designed to respond to various inputs describing changes in soil water content, plant status, and climate. Based on these inputs the system will determine the time and depth of application. This chapter describes the equipment and current state of the art with regard to automation of microirrigation systems.
Technical Abstract: Irrigation is the largest water user throughout the world. As the world population increases, there will be increased demand on irrigated agriculture to give up its water supply to meet the needs of municipal and industrial users and the environment. Microirrigation is one of the most efficient irrigation methods available and has the potential to operate at very high efficiencies. To meet this potential, it will be necessary to automate the system to meet the crop water requirement as closely as possible and control the application of nutrients to maximize the yield potential. This manuscript describes the theory of automated system control and the data and equipment needed to automate and operate a microirrigation system. Automation control requires a decision on when to irrigate and how much to irrigate. These are also the requirements of an irrigation schedule. The control methods described include: soil water potential measured using tensiometers and matric potential sensors, soil water content measured using TDR, FDR and water front advance, plant based methods, i.e., leaf turgor, leaf water potential, canopy temperature, and volume balance calculations that include soil water content, weather data, and measured irrigation application. Automation of microirrigation systems is gaining acceptance as the cost of electronics and the associated equipment is reduced. Other factors, i.e. labor availability, impact of irrigation on the environment, will also contribute to the adoption of automation.