Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 8/22/2012
Publication Date: 4/2/2013
Citation: Wang, D., Oshaughnessy, S.A., King, B.A. 2013. Automated irrigation management with soil and canopy sensing. In Q. Zhang and F.J. Pierce (eds.) Agricultural Automation - Fundamentals and Practices. Boca Raton, FL: CRC Press. pp. 295-321. Interpretive Summary: Automation in irrigation water management requires a systems approach with real time or near real time assessment of soil water status, crop water status, and an automated water delivery system, controlled with programmable electronics, either over an entire crop field as a whole or capable of applying variable rates to meet site-specific water needs. Irrigation scheduling decisions have often relied on direct or indirect measurement of soil water content or water potential. Any deployment or selection of soil sensors should take into consideration of crop type (rooting depth), soil type (sand versus clay), soil variability, and the mechanism of the sensors (contact - based or volume – based measurements). Techniques for assessment of plant water status for irrigation management have been developed and tested more recently. Spectral and thermal ground-based remote sensors mounted on self-propelled irrigation systems are capable of providing information to farmers in a timelier manner than aircraft or satellite sources. Infrared thermocouple thermometers mounted on a moving center pivot lateral can provide radiometric temperature measurements of in-field crop canopy. Software to control drip and moving sprinkler systems has been integrated with plant-feedback information and IRT measurements made from a moving sprinkler can then be used to provide spatial and temporal temperature maps that correspond to in-field water stress levels of crops. Automation in site-specific irrigation are mostly designed for center pivot and laetral move sprinkler irrigation systems. Recent advances and cost reduction in electronics (programmable logic controllers) and sensor technology (GPS and wireless sensors) and increased knowledge through research and development have resulted in commercially available irrigation systems fitted for variable rate or site-specific water applications. Fertilizer and pesticide injection into an irrigation stream can also be more site – specific as an added benefit. These developments not only help conserve water but also have the potential for reducing possible chemical loss to the environment. Future applications in irrigation automation will likely involve the integration of multiple sensor network systems for determining when to irrigate, where to irrigate, and how much to apply. The commercialization of sensors and sensor systems for irrigation automation in production agriculture will require reliable and economical wireless sensor network systems for ease of deployment and minimal maintenance. Such systems are already emerging as a result of the availability of affordable radio frequency modules, and wireless communication protocols.
Technical Abstract: Automated irrigation management provides for real time feedback between crop water needs and the delivery of specific amount of irrigation water to specific locations on demand. In addition to the basic components of any irrigation system, e.g. pumps, filters, valves, pipes and tubing, sprinkler heads or drip emitters, an automated system typically consists of a centralized electronic controller, soil and/or plant sensors, and/or GPS capabilities for inputing environmental measurements for making irrigation decisons. Sensors for measuring soil water status that are most suited for irrigation automation need to be able to generate electronic signals which are proportional to soil water content or soil water potential. Sensors for assessing in-field plant water status are mostly infrared thermometers (IRTs) mounted on a moving platform to provide radiometric canopy temperature measurements. For large scale center pivot and lateral move sprinkler systems, automation for site-specific irrigation application has been developed. Equipment and irrigation systems are commercially available for variable rate or site-specific water and chemical applications. Automation in irrigation management can save labor costs, improve water use efficiency, reduce energy consumption, reduce potential environmental impact, and help to make irrigated agriculture more sustainable.