Automatic Management Zone Delineation For Center Pivot Variable Rate Irrigation Using Field Data

Abstract

Highlights A computer model (MOPivot) was developed to determine unique management areas. MOPivot can delineate management zone maps for center pivot (CP) variable rate irrigation (VRI) systems. The CP system achieved high application uniformity over a range of VRI application depths. MOPivot management zone maps were evaluated using soil survey geographic database (SSURGO) and soil apparent electrical conductivity (ECa) data. 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 the 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 computer model (MOPivot) to automate management zone delineation for irrigation scheduling based on the minimum area that can be controlled by the CP system (based on sprinkler spacing and location, and wetted diameter) matched to VRI capabilities and GIS site-specific grid-based field data affecting water storage and runoff. To ensure that the CP was capable of meeting scheduled VRI prescriptions, application uniformity was validated along the lateral length for sprinkler pulse percentages of 20 to 100 percent using catch collectors spaced 3-m apart along thirteen radial lines (82 m long, beginning 68 m from the pivot point and covering 10° of pivot rotation) for both clockwise and counter-clockwise rotation. Results indicated that the system achieved high application uniformity over a range of VRI application depths. The MOPivot management zones were in close agreement with GIS grid-based soil survey geographic database (SSURGO) and soil apparent electrical conductivity (ECa) derived soil texture input data (82.8% and 93.5% overall accuracy, respectively). The model successfully established the minimum azimuthal angle and sector length for VRI zone-control VRI and automatically delineated management zones useful in developing Keywords: Center pivot, Irrigation prescription, Sprinkler zone, Variable rate irrigation.