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Morning crop water stress index as a sensitive indicator of water status in apple trees

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  2019 ASABE Annual International Meeting  1900577.(doi:10.13031/aim.201900577)
Authors:   Abdelmoneim Zakaria Mohamed, Yasin Osroosh, Troy Robert Peters, Travis Bates, Colin Sanford Campbell, Francesc Ferrer-Alegre
Keywords:   Crop water stress index, soil water deficit, soil matric potential, stem water potential, thermal sensing

Abstract. We compared the theoretical crop water stress index (CWSI) averaged over late morning hours (10:00-11:00 AM), (CWSImo) and over solar noon hours, midday (1:00-3:00 PM), (CWSImd). We assessed their sensitivity to changes in soil water content including soil water deficit, (SWD, %) and soil matric potential, (SMP, kPa) at different root zone depths, and to stem water potential (Ψstem). At the effective root zone depth, the linear relationship between SWD and CWSI averaged over morning hours resulted in a reasonably good correlation (R2 = 0.52, p < 0.001) compared with the traditional CWSI at midday (R2 = 0.45, p < 0.001). Also, SMP and CWSImo were well correlated (R2 = 0.63, P < 0.001), while it was slightly less correlated with CWSImd (R2 = 0.50, P < 0.001). There was a weak correlation between soil water content and both CWSImo and CWSImd at the depths 76 cm and 102 cm of the root zone. There was no statistically significant relationship between ψstem and both CWSImo and CWSImd. The CWSImo showed high sensitivity to soil water content that can be then used as a good indicator of water status in the root zone profile of apple trees.

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