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ARS Home » Plains Area » Fort Collins, Colorado » Center for Agricultural Resources Research » Water Management and Systems Research » Research » Publications at this Location » Publication #390858
Research Project: Improving the Sustainability of Irrigated Farming Systems in Semi-Arid Regions

Location: Water Management and Systems Research

Title: Crop water stress index computation approaches and their sensitivity to soil water dynamics

Author
item KATIMBO, ABIA - University Of Nebraska
item RUDNICK, DARAN - University Of Nebraska
item DeJonge, Kendall
item LO, TSZ - Mississippi State University
item QIAO, XIN - University Of Nebraska
item FRANZ, TRENTON - University Of Nebraska
item NAKABUYE, HOPE - University Of Nebraska
item DUAN, JIAMING - University Of Nebraska

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2022
Publication Date: 5/31/2022
Citation: Katimbo, A., Rudnick, D.R., DeJonge, K.C., Lo, T.H., Qiao, X., Franz, T., Nakabuye, H.N., Duan, J. 2022. Crop water stress index computation approaches and their sensitivity to soil water dynamics. Agricultural Water Management. 266. Article e107575. https://doi.org/10.1016/j.agwat.2022.107575.
DOI: https://doi.org/10.1016/j.agwat.2022.107575

Interpretive Summary: There is a growing interest of using canopy temperature (Tc) based methods, including crop water stress index (CWSI), for irrigation management. However, different approaches exist to normalize Tc to microclimatic conditions, which can influence the accuracy and suitability of CWSI for irrigation scheduling. This study evaluated the performance of CWSI computation approaches and their sensitivity to changes in soil water depletion under different water stress levels as well as the uncertainties of each approach under varying weather conditions. Results suggest that careful selection of appropriate computational approaches and irrigation triggering thresholds for CWSI is desired.

Technical Abstract: There is a growing interest of using canopy temperature (Tc) based methods, including crop water stress index (CWSI), for irrigation management. However, different approaches exist to normalize Tc to microclimatic conditions, which can influence the accuracy and suitability of CWSI for irrigation scheduling. This study evaluated the performance of CWSI computation approaches and their sensitivity to changes in soil water depletion under different water stress levels as well as the uncertainties of each approach under varying weather conditions. There were six different approaches – two empirical methods using developed lower baseline (i.e., CWSI-EB1, CWSI-EB2), two empirical methods using either artificial (CWSI-EA) or actual/natural (CWSI-EN) canopy reference surfaces, and two theoretical approaches which differ by how aerodynamic and canopy resistances are determined (CWSI-Th1, CWSI-Th2). Stationary infrared thermometers (IRTs) provided Tc to calculate CWSI-EB, CWSI-Th, and CWSI-EN; whereas mobile IRTs and a thermal camera provided Tc and temperatures of artificial canopy reference surfaces to calculate CWSI-EA. These measurements were collected from full and deficit irrigated and rainfed maize plots in West Central Nebraska. Day-to-day variations within and across CWSI approaches were evident and their sensitivity to soil water depletion varied. High sensitivity to depletion (Dr,i) was observed for CWSI-Th and CWSI-EB under severe stress (i.e., Dr,i between 65 and 75%) with r2 ranging from 0.61 to 0.80 and 0.69 to 0.79, respectively. Additionally, it was observed that CWSI sensitivity was influenced more by the clearness of the sky (i.e., Rs/Rso) than other weather variables. Observed variability and instability of CWSI under fluctuating weather conditions suggest that careful selection of appropriate computation approach and triggering threshold is desired.