Quantifying water stress in vineyards using a smartphone

There is an increasing demand for tools able to optimise water management in cropping systems, especially in cases of dry areas or when water management has a deep effect on both the amount and quality of productions. A method is proposed to estimate grape stomatal conductance (g(s)) from 3D leaf scans obtained using a smartphone. The method is based (i) on the use of the 3D leaf scans to derive the chi parameter of the Campbell's leaf angle distribution (the lower the chi, the larger the leaf tendency to be vertical) and (ii) on the changes in leaf orientation due to decrease in leaf turgor. Experimental data were collected on Vitis vinifera (cv. Malvasia and Chardonnay) in seven experiments carried out in vineyards in Northern Italy during 2021 and 2022. Results revealed significant (p-value < 0.01) linear relationships between g(s) and chi (R-2 >= 0.79 for both cultivars). From the data collected, 13 leaves (90 s to perform measurements) at each point (vine) and seven points ha(-1) was identified as the optimal sample size to capture vineyard heterogeneity. The suitability of the method for use in commercial vineyard conditions opens new opportunities for optimizing water management in vineyards.