Grapevine, Berry and Soil Indicators to Manage Minimal Irrigation Strategy in Semi-Arid Conditions: Example of Grenache Noir (Vitis vinifera L.)

The combination of low rainfall, high evapotranspiration and low water availability under semi-arid conditions necessitates rethinking cultural practices including the use of irrigation. This article aims to present necessary soil-climate and vegetative-berry development variables to be considered to manage a minimal irrigation for ensuring yield consistency and avoiding potential inhibition of berry development and maturation. A two-year study (2022-2023) was conducted on 'Grenache N'. (Vitis vinifera L.) grafted onto 110R in commercial vineyards located in the wine region of Pyrénées-Orientales (PO), South of France. One drip-irrigated and one rainfed treatment were compared. Among the main findings of this study, the relationship between soil water content and predawn leaf water potential differed for irrigated treatment compared to the rainfed treatment. This highlights the need for a proper calibration curve between these two variables when considering drip irrigation. In addition, the monitoring of the evolutions of berry sugar and organic acids, in parallel with the evolution of berry volume (or fresh mass), permitted to evaluate the impact of water supply on vine water and carbon functioning and achieve minimal irrigation. When local water availability for irrigation is limited (less than 500 m³ per hectare per year), such soil, plant and berry measurements at key stages can make the difference and help surpass physiological limits. This study ultimately proposes an easy-to-conduct field method to help winegrowers achieve predefined yield and wine quality targets while minimizing their water footprint.