Field heterogeneity of soil texture controls leaf water potential spatial distribution predicted from UAS-based vegetation indices in non-irrigated vineyards

Abstract. Grapevine water status exhibits substantial variability even within a single vineyard. Understanding how edaphic, topographic, and climatic conditions impact grapevine water status heterogeneity at the field scale, in non-irrigated vineyards, is essential for winemakers as it significantly influences wine quality. This study aimed to quantify the spatial distribution of grapevine leaf water potential (Ψleaf) within vineyards and to assess the influence of soil property heterogeneity, topography, and climatic conditions on intra-field variability in two non-irrigated vineyards during two viticultural seasons. By combining multilinear vegetation indices from very-high-spatial-resolution multispectral, thermal, and lidar imageries collected with uncrewed aerial systems (UASs), we efficiently and robustly captured the spatial distribution of Ψleaf across both vineyards on different dates. Our results demonstrated that in non-irrigated vineyards, the spatial distribution of Ψleaf was mainly governed by the within-vineyard soil hydraulic conductivity heterogeneity (R2 up to 0.81) and was particularly marked when the evaporative demand and the soil water deficit increased, since the range of Ψleaf was greater, up to 0.73 MPa, in these conditions. However, topographic attributes (elevation and slope) were less related to grapevine Ψleaf variability. These findings show that the soil property within-field spatial distribution and climatic conditions are the primary factors governing Ψleaf heterogeneity observed in non-irrigated vineyards, and their effects are concomitant.