There is increasing pressure on our water resources, which prompts us to manage our water more precisely. With an increasing demand for food production, variable rate irrigation (VRI) is a technology that may improve irrigation water productivity (yield produced per unit of water diverted for irrigation). While VRI is not likely to reduce the consumptive use of water (i.e. evapotranspiration), VRI may reduce pumping for irrigation, resulting in energy savings and reduced deep percolation of water below the root zone. Reduced leaching of nitrates from the soil would improve water quality in aquifers. VRI has many potential applications, and the specific benefits of each application should be quantified in order to inform producers who are considering whether to invest in VRI technology. Research is also needed to develop a decision support system that would automate the process of making dynamic irrigation prescription maps for VRI management.
Past research includes a method for field characterization of root zone available water capacity (Lo et al., 2017); a method for making irrigation prescription maps based on soil properties (Miller et al., 2017); an evaluation of control scenarios for prescription maps (Miller et al., 2017); and an analysis of the number of soil water monitoring locations required for VRI management zones (Barker et al., 2017a). A statewide analysis of potential pumping reductions from VRI estimated that pumping reductions would exceed two inches per year for 2% of the fields and would exceed one inch per year for 13% of the fields in Nebraska (Lo et al., 2016). An economic framework for decisions about whether to invest in VRI indicated that use of VRI to improve yield may have the greatest potential to economically justify an investment in a VRI system (chapter 1 of Lo, 2015).
Remote sensing imagery from satellites was used along with the SETMI model in order to quantify spatial variability in ET (Barker et al., 2017b) and to develop VRI prescription maps. Field implementation of prescription maps demonstrated that effective management of VRI will likely require a combination of both remote sensing and soil water monitoring (Barker et al. 2017a; Barker et al., 2017c). VRI based on soil water sensors reduced irrigation by 0.5 in for soybeans and by 0.1 in for corn (Barker et al., 2017c). Ongoing research is utilizing imagery from unmanned aircraft and is continuing to develop SETMI as a decision support tool for VRI management.
Map for VRI Pumping Reduction
This map tool provides an estimate of pumping reduction from using VRI to mine undepleted soil water.
Refereed Journal Articles
- Barker, J. B., D. M. Heeren, C. M. U. Neale, and D. R. Rudnick. 2017c. Response of maize and soybean to variable rate irrigation using soil water content monitoring and a remote-sensing-based water balance model. Agricultural Water Management (aceepted).
- Barker, J. B., C. M. U. Neale, D. M. Heeren, and A. E. Suyker. 2017b. Evaluation of a hybrid reflectance-based crop coefficient and energy balance evapotranspiration model for irrigation management. Transactions of the ASABE (in press).
- Barker, J. B., T. E. Franz, D. M. Heeren, C. M. U. Neale, and J. D. Luck. 2017a. Soil water content monitoring for irrigation management: A geostatistical analysis. Agricultural Water Management 188: 36-49, doi: 10.1016/j.agwat.2017.03.024.
- Miller, K. A., J. D. Luck, D. M. Heeren, T. Lo, D. L. Martin, and J. B. Barker. 2017. A geospatial variable rate irrigation control scenario evaluation methodology based on mining root zone available water capacity. Precision Agriculture, doi: 10.1007/s11119-017-9548-z.
- Lo, T., D. M. Heeren, L. Mateos, J. D. Luck, D. L. Martin, K. A. Miller, J. B. Barker, and T. M. Shaver. 2017. Field characterization of field capacity and root zone available water capacity for variable rate irrigation. Applied Engineering in Agriculture 33(4): 559-572, doi: 10.13031/aea.11963.
- Lo, T., D. M. Heeren, D. L. Martin, L. Mateos, J. D. Luck, and D. E. Eisenhauer. 2016. Pumpage reduction by using variable rate irrigation to mine undepleted soil water. Transactions of the ASABE 59(5): 1285-1298, doi: 10.13031/trans.59.11773.
- Finkenbiner, C. E., T. E. Franz, J. Gibson, D. M. Heeren, and J. D. Luck. Integration of hydrogeophysical datasets for improved water resource management in irrigated systems. Precision Agriculture (in review).
Other Relevant Products
- Extension Article: Heeren, D. M., J. B. Barker, T. Lo, S. R. Melvin, D. L. Martin, and J. D. Luck. 2017. Considerations in adopting variable rate irrigation. UNL Water website.
- Invited Presentation: 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.
- Extension Conference Paper: Barker, J. B., D. M. Heeren, and C. M. U. Neale. 2016. Perspectives on VRI prescription map development with satellite imagery.
- Extension Conference Paper: Lo, T., D. M. Heeren, and J. D. Luck. 2016. Spatial mapping of root zone water holding capacity for site-specific management.
- Conference Proceedings: Barker, J. B., C. M. U. Neale, and D. M. Heeren. November 10-12, 2015. Evaluation of a hybrid remote sensing evapotranspiration model for variable rate irrigation management. Joint ASABE and Irrigation Association (IA) Irrigation Symposium, Paper No. 2147813, Long Beach, Calif.
- Lecture: Heeren, D. M., J. D. Luck, T. Lo, and J. B. Barker. 2015. Variable rate irrigation (VRI): Principles and lab setup. MSYM 452 Irrigation Systems Management.
- Dissertation: Barker, J. B. 2017. Spatial irrigation management using remote sensing water balance modeling and soil water content monitoring.
- Thesis: Lo, T. 2015. Quantification of variable rate irrigation benefits and spatial variability in root zone water holding capacity.
- News video: USDA grant funds research in VRI management using unmanned aircraft systems
- News video: Burdette Barker receives University of Nebraska Presidential Fellowship for VRI research
- Extension publication on VRI