Mapping Grapevine ( Vitis vinifera L.) Water Status during the Season Using Carbon Isotope Ratio (δ 13 C) as Ancillary Data

Abstract

Vine water status is a major parameter for vine management because it affects both wine quality and yield. In order to optimize vineyard management and harvesting practices, it is necessary to characterize vineyard water status spatial variability. This work aims at establishing an empirical spatial model for stem water potential (Ψ_Stem) with ancillary data based on vine water status. Carbon isotope ratio (δ¹³C) measured at harvest was selected as ancillary data because it reflects only the effect of vine water status variations integrated over the season and is not impacted by other factors such as vine nitrogen status. The proposed model was applied at the intrablock level. It is based on the spatial extrapolation of a Ψ_Stem value measured at a reference site using δ¹³C values collected over the block. Measurements of Ψ_Stem and δ¹³C were carried out over three consecutive years on 96 locations within the block. Ψ_Stem values obtained with a spatial model were more accurate than Ψ_Stem values obtained with a nonspatial model, indicating the relevancy of δ¹³C values to account for spatial variability of vine water status. Results show that operational maps of vine water status can be obtained by means of a spatial model, in which δ¹³C values from a previous season are used as ancillary data. Maps can be updated at any given time during the season by carrying out a limited number of Ψ_Stem measurements in selected locations. This model offers a tool to monitor vine water status and to implement management practices while considering vine water status intrablock variability.