A variable-rate irrigation decision support system for corn in the U.S. Eastern Coastal Plain

Authors: Stone, Kenneth - Ken; BAUER, PHILIP - Retired ARS Employee; O`Shaughnessy, Susan; ANDRADE-RODRIGUEZ, ALEJANDRO - University Of Nevada; Evett, Steven - Steve

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2020
Publication Date: 10/14/2020
Citation: Stone, K.C., Bauer, P.J., Oshaughnessy, S.A., Andrade-Rodriguez, A., Evett, S.R. 2020. A variable-rate irrigation decision support system for corn in the U.S. Eastern Coastal Plain. Transactions of the ASABE. 63(5):1295-1303. https://doi.org/10.13031/trans.13965.
DOI: https://doi.org/10.13031/trans.13965

Interpretive Summary: Variable rate irrigation (VRI) systems water at different depths both in the direction of travel and along the length of the irrigation system and are capable of improving crop water management and efficiency. VRI technology has had limited adoption due to additional management required. To address this, a decision support system that utilizes remote sensing plant, soil, and microclimate to schedule VRI irrigations was developed by USDA-ARS. In our research, we evaluated the use of the USDA-ARS Irrigation Scheduling and Supervisory Control and Data Acquisition System (ISSCADA) for spatially managing corn irrigation with a VRI irrigation system in the US Eastern Coastal Plain. The ISSCADA system consists of center pivot mounted infrared thermometers to measure crop canopy temperatures and field soil moisture sensors. The ISSCADA system collects spatial crop temperature, calculates crop water stress, and provides a spatial irrigation recommendation that can be downloaded to the VRI system. We compared the ISSCADA system with a popular irrigation scheduling method using measured soil water potentials for four years. In the first two years of the study, there was adequate rainfall and little irrigation was required. In these first two years the corn yields and water use efficiency were not significant different between the irrigation treatments. In the last two years of the study, midseason drought conditions and sporadic rainfall patterns required frequent irrigations. In the last two years, the irrigation treatment corn yields were not significantly different from each other but were much greater than the rainfed yields. In the last two years of the study, a modified ISSCADA treatment was used that produced higher corn yields and required less irrigation than the standard ISSCADA treatment. Results from this experiment will help to evaluate and refine the ISSCADA system to provide a tool for growers to use in managing spatial irrigation with variable rate irrigation systems.

Technical Abstract: Variable rate irrigation (VRI) systems are capable of applying different water depths both in the direction of travel and along the length of the irrigation system. These VRI systems maybe useful for improving crop water management and efficiency. Although VRI technology is available and has high grower interest, it has had limited adoption. To address this, researchers have developed a decision support system that utilizes remote sensing plant, soil, and microclimate to schedule VRI irrigations. In this research, we evaluated the use of the USDA-ARS Irrigation Scheduling and Supervisory Control and Data Acquisition System (ISSCADA) for spatially managing corn irrigation in the US Eastern Coastal Plain. The ISSCADA system consists of center pivot mounted infrared thermometers to measure crop canopy temperatures and field soil moisture sensors. An integrated crop water stress index (iCWSI) was calculated from the canopy temperatures. The ISSCADA system analyzes the iCWSI and soil moisture measurements to provide an irrigation recommendation. The ISSCADA system was evaluated using 1) only the iCWSI and 2) with a Hybrid-ISSCADA system using both iCWSI and soil moisture depletion criteria. These ISSCADA treatments were compared to traditional irrigation management using measured soil water potentials. The ISSCADAS System was evaluated for 4-years. In 2016 and 2017, corn yields and water use efficiency were not significant different between the irrigation treatments due to adequate rainfall during the growing season. In 2018 and 2019, mid-season drought conditions and sporadic rainfall patterns required frequent irrigations. In both years, the irrigation treatment corn yields were not significantly different from each other but were greater than the rainfed yields. In 2018, the irrigation treatments produce corn yields of 10.7, 10.4, 10.1 Mg ha-1, for the Hybrid, ISSCADA, and SWP treatments, respectively. Over the four-year study, the water use efficiencies of the irrigation treatments were not significantly different from each other or the rainfed treatment and ranged from 16.6 to 22.7 kg ha-1 mm-1. In the two years that the Hybrid-ISSCADA was used for managing irrigations, it produced higher corn yields and required less irrigation than the standard ISSCADA treatments. Results from this experiment will help to evaluate and refine the ISSCADA system to provide a tool for growers to use in managing spatial irrigation with variable rate irrigation systems.