Automatic management zone delineation for center pivot variable rate irrigation using field data

Authors: NGUYEN, ANH - University Of Missouri; THOMPSON, ALLEN - University Of Missouri; Sudduth, Kenneth - Ken; VORIES, EARL - Retired ARS Employee

Submitted to: Journal of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2023
Publication Date: 12/15/2023
Citation: Nguyen, A., Thompson, A.L., Sudduth, K.A., Vories, E.D. 2023. Automatic management zone delineation for center pivot variable rate irrigation using field data. Journal of the ASABE. 66(6):1527-1545. https://doi.org/10.13031/ja.15528.
DOI: https://doi.org/10.13031/ja.15528

Interpretive Summary: Center pivot-based variable rate irrigation (VRI) allows changing the prescribed amount of water as the irrigation machine moves across a field. As with other variable rate applications such as fertilizer, physical limitations of the machine mean that the actual application rate changes will differ from prescribed rate changes, and that the physical characteristics of the irrigation machine need to be considered in developing an application plan. This study created software to automate creation of such application plans for center pivot systems based on machine characteristics and mapped field data. The MOPivot software requires the user to input specific pivot system information and the desired water application plan. The software can be used on all common types of center pivot VRI systems – those with individual sprinkler control, defined sprinkler zones, or system rotation speed changes. The results from this study will help provide irrigation engineers with a new tool to optimize VRI prescriptions with respect to system operating characteristics.

Technical Abstract: Concerns over water availability and water quality increasingly require more efficient use of water resources in irrigated agriculture. Center pivot (CP) systems designed with variable rate irrigation (VRI) technology have potential to improve application and water-use efficiency while reducing environmental impacts from excess runoff and poor water quality. The objective of this study was to develop a decision support tool (MOPivot software) to create automated irrigation prescriptions based on CP geometry and system characteristics (sprinkler spacing and location, and wetted diameter) defining the minimum unique management area along the lateral during pivot rotation. The minimum management area was further delineated based on site specific soil conditions affecting water storage and runoff. The MOPivot management zones were in close agreement with GIS grid-based input data (82.8% and 93.5% overall accuracy with SSURGO and ECa soil texture, respectively). Validation of CP application uniformity was based on field data collected along the lateral length using catch collectors spaced approximately 3-m apart along thirteen radial lines (RL) (82 m long beginning 68 m from the pivot point and covering 10o of pivot rotation) for both clockwise and counter-clockwise rotation. The VRI application rates were varied from 20% to 100% in 20% increments. Results indicated that the system was capable of achieving a high application uniformity over a range of VRI application depths. A scheduled application rate change within a VRI zone was represented by an approximate linear transition in application depth across the wetted sprinkler diameter along the lateral arc rather than an abrupt change between adjacent zones. The MOPivot program can be used on VRI systems with individual sprinkler control, defined sprinkler zones, or system rotation speed changes.