|Evett, Steven - Steve|
Submitted to: Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 8/1/2008
Publication Date: 10/20/2008
Citation: Evett, S.R., Howell, T.A. 2008. Role of irrigation and irrigation automation in improving crop water use efficiency [abstract]. In: Proceedings of International Symposium on Water in Agriculture and Forestry: Challenges, Technological Solutions and Innovations, October 21-23, 2008, Beijing, China. p.16.
Technical Abstract: In arid climates, irrigation is required for significant agricultural production. In subhumid and semiarid climates, supplemental irrigation is recognized as both economically necessary (prevention of crop losses in periodic droughts) and as a means to improve overall crop water use efficiency (WUE); and for these reasons irrigation is increasing in subhumid and even humid climates. It has long been recognized that irrigation management affects crop water use efficiency; for example, FAO Irrigation and Drainage Paper 33, Yield Response to Water (1979). Perhaps overlooked is the fact that irrigation generally improves overall WUE to as much as double that which can be obtained when production relies on precipitation alone. We discuss data from winter wheat studies underscoring this point. More recently, the severe water shortages in the face of increasing demands for food experienced in much of the world have led to renewed interest in controlled deficit irrigation as a means to improve WUE, e.g., FAO Water Report 22, Deficit Irrigation Practices (2002). Currently, we are cooperating with the FAO Land and Water Division in development of the AquaCrop model of crop yield and water use. AquaCrop, which is being tested and parameterized with more recent data, is intended to be a more robust approach than the more empirical one in FAO 33 to provide a more mechanistic method for determining how irrigation management may be modified to improve WUE. However, the irrigation scheduling methods used to develop the accurate data in publications such as FAO 33, 22 and the AquaCrop model, are often not useable outside research environments. For example, irrigating to replenish soil water to the field capacity level or some fraction thereof, using the neutron moisture meter to measure water content, is infeasible for most irrigators. We show that other, more automated soil water measurement methods have been found to be too inaccurate for accurate irrigation scheduling. We present an irrigation automation method that has been used with both drip and sprinkler irrigation systems and which is based on canopy temperature measurements and a feedback loop for stability. Particularly for C4 crops, control parameters for this automation method may be set to improve water use efficiency while maintaining yield at reasonable levels.