ARSPivot, A Sensor-Based Decision Support Software for Variable-Rate Irrigation Center Pivot Systems: Part B. Application

The ARSPivot software was developed for the seamless operation of a complex network consisting of a variablerate irrigation (VRI) center pivot system and an Irrigation Scheduling Supervisory Control and Data Acquisition (ISSCADA) system that interfaces with weather, plant, and soil water sensing systems. ARSPivot's graphical user interface (GUI) incorporates a built-in geographic information system (GIS) that maps a center pivot system and facilitates the analysis of data relevant to its operation. The GIS was developed following a minimalistic approach with the objective of making its geospatial data analysis tools accessible to a wide range of users (farmers, irrigation consultants, and researchers). The post-harvest analyses of two experiments carried out in the Texas High Plains during the summers of 2016 and 2017 using a three-span VRI center pivot are presented to illustrate the advantages of using ARSPivot as a decision support tool and how its GIS tools help its users make better informed decisions regarding irrigation management. In these experiments, the north-northwest (NNW) portion of a field planted with corn (Zea mays L.) was irrigated using VRI zone control, and the south-southeast (SSE) portion was irrigated using VRI speed control. Experimental plots in the NNW portion were assigned one of three irrigation levels (80%, 50%, or 30% replenishment of soil water depletion to field capacity in the top 1.5 m), and their irrigation was scheduled using either a plant stress-based algorithm implemented in the ARSPivot software or manual weekly neutron probe (NP) readings. Plots in the SSE portion were assigned a single irrigation level of 80%, and their irrigation was scheduled using either the plant stress method or a two-step hybrid approach in which soil water sensing was combined with the plant stress method to determine irrigation depths. Soil water sensing data for the ISSCADA system were provided by NP readings during the 2016 season and by sets of time-domain reflectometers (TDRs) installed at depths of 15, 30, and 45 cm during the 2017 season. No significant differences were found during either season in terms of mean dry grain yield and crop water productivity (CWP) obtained from plots irrigated at the 80% level in both sides of the field, regardless of the irrigation scheduling method or the type of VRI application method used for irrigation. No significant differences were found during either season between mean dry grain yield and CWP of plots in the NNW portion irrigated using the plant stress-based method and NP readings at the 80% irrigation level. The lack of significant differences documented the potential of the ARSPivot system as a plant and soil water sensing-based decision support software for sitespecific irrigation management of corn using a VRI center pivot system.