Diurnal and seasonal mapping of water deficit index and evapotranspiration by an unmanned aerial system: A case study for winter wheat in denmark

Vita Antoniuk*, Kiril Manevski, Kirsten Kørup, Rene Larsen, Inge Sandholt, Xiying Zhang, Mathias Neumann Andersen

*Corresponding author for this work

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    Precision irrigation is a promising method to mitigate the impacts of drought stress on crop production with the optimal use of water resources. However, the reliable assessment of plant water status has not been adequately demonstrated, and unmanned aerial systems (UAS) offer great potential for spatiotemporal improvements. This study utilized UAS equipped with multispectral and thermal sensors to detect and quantify drought stress in winter wheat (Triticum aestivum L.) using the Water Deficit Index (WDI). Biennial field experiments were conducted on coarse sand soil in Denmark and analyses were performed at both diurnal and seasonal timescales. The WDI was significantly correlated with leaf stomatal conductance (R2 = 0.61–0.73), and the correlation was weaker with leaf water potential (R2 = 0.39–0.56) and topsoil water status (the highest R2 of 0.68). A semi-physical model depicting the relationship between WDI and fraction of transpirable soil water (FTSW) in the root zone was derived with R2 = 0.74. Moreover, WDI estimates were improved using an energy balance model with an iterative scheme to estimate the net radiation and land surface temperature, as well as the dual crop coefficient. The diurnal variation in WDI revealed a pattern of the ratio of actual to potential evapotranspiration, being higher in the morning, decreasing at noon hours and ‘recovering’ in the afternoon. Future work should investigate the temporal upscaling of evapotranspiration, which may be used to develop methods for site-specific irrigation recommendations.

    Original languageEnglish
    Article number2998
    JournalRemote Sensing
    Issue number15
    Number of pages25
    Publication statusPublished - 2021

    Bibliographical note

    This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).


    • Drought stress
    • Energy balance
    • Fraction of transpirable soil water
    • Temperature trapezoid
    • Thermal imagery
    • Vegetation index


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