Variable Rate Irrigation

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

Other Relevant Products

Links

  • 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