Potential irrigation reductions from increasing precipitation utilization with variable rate irrigation

Much of the previous research quantifying the potential benefits of variable rate irrigation (VRI) consists of case studies with simulations using data from small numbers of intensely sampled fields. In this study, an indicator of the amount of root zone available water capacity that is unutilized by uniform rate irrigation was calculated for 49,224 center pivot irrigated fields in Nebraska using publicly available data exclusively. Based on the values of this indicator, potential seasonal irrigation reductions from increasing precipitation utilization with VRI were estimated to be high for a small fraction of analyzed center pivots but low on a regional scale. At current VRI and energy prices, pumping cost savings alone may fail to justify VRI adoption for most analyzed center pivots. Although the prevalence of center pivots with high indicator values differed among counties and among soil associations, ruling out with reasonable confidence the occurrence of either low or high indicator values in a county or soil association might be difficult. The study hopes to inform producers considering VRI and other entities interested in the potential impact of this particular application of VRI.