Luca Brillante, W.C. Cheng, M. Andy Walker, Andrew McElrone, and Kaan Kurtural*
*University of California Davis, 1 Shields Avenue, Davis, CA 95616 (skkurtural@ucdavis.edu)

A proximal sensing method was developed as a novel non-invasive method (electrical resistivity tomography, ERT) to compare dynamic changes in root growth and water uptake by rootstocks used in vineyards. An experiment was conducted with three replicates of four plants of 110R and 101-14 MG onto which Chardonnay was grafted, which were not irrigated during the 2017 field season to reach a severe water stress status. Primary metabolism was characterized by predawn, and stem water potentials throughout the day, carbon isotopic discrimination of sugars (dC13), and stomatal conductance and net leaf carbon assimilation were also measured. Plant vigor and nutrition were assessed by pruning weights and mineral nutrient analysis, respectively. During the dormant season, three soil pits were opened in each experimental unit to analyze the soil and install TDR sensors. At the end of season, roots were sampled, separated from the soil and weighed, then ERT in 2D and 3D was performed. ERT was corrected by the temperature and reported to a standard temperature of 25°C, then two different pedoelectrical models were fitted. The Archie model performed better and allowed transformation of electrical resistivity into soil volumetric water with an error of 1.2% volune (R2 = 0.73). The first 3D images of water distribution under grapevine were obtained, and up to one-fold of spatial differences in the quantity of water absorbed between grapevines was measured in the two rootstocks. Spatial distribution of water correlated significantly to predawn water potential in both rootstocks. 110R and 101-14Mg showed contrasting water uptake behavior that was related to greater pruning mass and water stress that were significantly different between rootstocks. Water distribution correlated with the presence of roots and was used to develop the first electrical image of the root distribution of a grapevine in situ.

Funding Support: American Vineyard Foundation