Agricultural and Biological Systems Engineering, Department of
Department of Agricultural and Biological Systems Engineering: Presentations and White Papers
Date of this Version
11-2016
Document Type
Presentation
Citation
Heeren, D. M., T. Lo, J. D. Luck, J. B. Barker, D. L. Martin, and L. Mateos. November 8, 2016. Variable rate irrigation for mining undepleted soil water. International Committee on Irrigation and Drainage (ICID) World Irrigation Forum, Chiang Mai, Thailand.
Abstract
Variable Rate Irrigation (VRI) offers the potential to improve irrigation efficiency by accounting for spatial variability in soil properties and water-holding capacity. This study explores the hypothesis that under conventional uniform irrigation, portions of fields with higher root zone available water capacity (R) often retain undepleted soil water. By developing prescription maps based on management allowable depletion (MAD), VRI can strategically “mine” this undepleted soil water, thereby reducing pumping requirements without negatively affecting crop performance.
Multiple tools for identifying spatial variability—including yield maps, digital elevation models, apparent electrical conductivity (ECa), soil sampling, remote sensing imagery, and cosmic ray probes—were evaluated for their role in generating VRI prescriptions. A GIS-based analysis of 49,224 center pivots across Nebraska using USDA gSSURGO soil data estimated that mining undepleted soil water could reduce pumping by more than 25 mm on 13% of fields and more than 51 mm on 2% of fields . Field testing demonstrated that root zone water-holding capacity correlated more strongly with elevation than with ECa, and that field-measured data suggested greater pumping reduction potential than soil survey estimates.