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., 2018); an evaluation of control scenarios for prescription maps (Miller et al., 2018). 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).
Remote sensing imagery from satellites was used along with the SETMI model in order to quantify spatial variability in ET 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., 2018). VRI based on soil water sensors reduced irrigation by 0.5 inch for soybeans and by 0.1 inch for corn (Barker et al., 2018). 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 for 49,000 fields in Nebraska.
- Bhatti, S., D. M. Heeren, J. B. Barker, C. M. U. Neale, W. E. Woldt, M. S. Maguire, and D. R. Rudnick. 2020. Site-specific irrigation management in a sub-humid climate using a spatial evapotranspiration model with satellite and airborne imagery. Agricultural Water Management 230, doi: 10.1016/j.agwat.2019.105950.
- Barker, J. B., W. E. Woldt, B. D. Wardlow, M. S. Maguire, B. C. Leavitt, C. M. U. Neale, and D. M. Heeren. 2020. Calibration of a common shortwave multispectral camera system for quantitative agricultural applications. Precision Agriculture 21: 922-935, doi: 10.1007/s11119-019-09701-6.
- Barker, J. B., S. Bhatti, D. M. Heeren, C. M. U. Neale, and D. R. Rudnick. 2019. Variable rate irrigation of maize and soybean in West-Central Nebraska under full and deficit irrigation. Frontiers in Big Data 2(34), doi: 10.3389/fdata.2019.00034.
- O’Shaughnessy, S. A., S. R. Evett, P. D. Colaizzi, M. A. Andrade, T. H. Marek, D. M. Heeren, F. R. Lamm, and J. L. LaRue. 2019. Identifying advantages and disadvantages of variable rate irrigation – an updated review. Applied Engineering in Agriculture 35(6): 837-852, doi: 10.13031/aea.13128.
- Barker, J. B., D. M. Heeren, C. M. U. Neale, and D. R. Rudnick. 2018. Evaluation of variable rate irrigation using a remote-sensing-based model. Agricultural Water Management 203: 63-74, doi: 10.1016/j.agwat.2018.02.022.
- Miller, K. A., J. D. Luck, D. M. Heeren, T. Lo, D. L. Martin, and J. B. Barker. 2018. 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.
- Extension NebGuide: Lo, T., D. R. Rudnick, Y. Ge, D. M. Heeren, S. Irmak, J. B. Barker, X. Qiao, T. M. Shaver. 2018. Ground-based thermal sensing of field crops and its relevance to irrigation management.
- 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.