Evaluation of infrared canopy temperature data in relation to soil water-based irrigation scheduling in a humid subtropical climate

Authors: LENA, BRUNO - Auburn University; ORTIZ, BRENDA - Auburn University; JIMENEZ-LOPEZ, ANDRES - University Of The Llanos; SANZ-SAEZ, ALVARO - Auburn University; Oshaughnessy, Susan; DURSTOCK, MARY - Auburn University; PATE, GREG - Auburn University

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2020
Publication Date: 9/1/2020
Publication URL: https://handle.nal.usda.gov/10113/7175910
Citation: Lena, B.P., Ortiz, B.V., Jimenez-Lopez, A.F., Sanz-Saez, A.K., O'Shaughnessy, S.A., Durstock, M.K., Pate, G. 2020. Evaluation of infrared canopy temperature data in relation to soil water-based irrigation scheduling in a humid subtropical climate. Transactions of the ASABE. 63(5):1217-1231. https://doi.org/10.13031/trans.13912.
DOI: https://doi.org/10.13031/trans.13912

Interpretive Summary: As water for agriculture in the western semi-arid regions of the US becomes more scarce, irrigated crop production continues to move eastward. Producers in the eastern US could benefit from sensor-based irrigation scheduling methods. However, methods developed for the western US may not be applicable for irrigation scheduling of crops in sub-humid and humid climates and producers in this region are not familiar with canopy temperature methods. In this two-year study, a post-analysis of canopy temperature data from corn irrigated at three different levels was used to determine if the Time Temperature Threshold (TTT) and the Crop Water Stress Index (CWSI) methods would trigger irrigations at the same frequency as the control method of using soil water sensors installed within the rootzone. Results showed that the TTT method would likely result in over-irrigation of corn. However, if a non-stressed baseline is established for humid regions, the CWSI could potentially be used to trigger irrigations at the same frequency as soil water sensors in the rootzone. This finding is important because canopy temperature measurements can be made from moving platforms, including sprinkler irrigation systems, and therefore provide information to producers to make irrigation scheduling decisions at a greater spatial resolution than soil water sensors.

Technical Abstract: Irrigation scheduling based on crop water stress index (CWSI) and temperature-time threshold (TTT) methods is promising. The objective of this study was to investigate the performance of the CWSI and TTT methods as irrigation signaling tools for a humid environment in the Southeastern USA. Corn canopy temperature data was collected in Alabama in 2018 and 2019 using infrared leaf temperature sensors for a fully irrigated treatment and two limited irrigation treatments. A set of three soil-water sensors installed at 0.15, 0.3, and 0.6 m soil depth were used to prescribe irrigation time and amount. CWSI showed to be sensitive to precipitation, irrigation or plant water uptake. No statistical difference of CWSI nor yield among the three irrigation levels were found in 2018. It was explained by the fact that precipitation was well distributed during the season. Contrastingly in 2019, both CWSI and yield differed statistically among the three irrigation levels. In 2019, precipitation events were sparse compared with 2018, and irrigation promoted higher differences in water availability among the treatments. The inconsistencies of the TTT method with or without the inclusion of the limiting relative humidity algorithm show that this method may not be a reliable irrigation signaling tool for humid environments.