Soil electrical resistivity measurement: from terroir characterization to within-field crop inputs management

Pinking describes the appearance of a salmon-red blush in white bottled wines produced exclusively from white grape varieties. It is understood as an undesirable chromatic phenomenon by both wine consumers and the industry. Nowadays, there are no treatments to fully reverse pinking once it occurs. Partial reversion has been shown after exposure of pinked wine to ultraviolet (UV) light.

Tannins are a heterogenous class of polymeric phenolics found in grapes, oak barrels and wine. In red wine tannins are primarily responsible for astringency, though they also have an important role in reacting with and stabilizing pigments. There are numerous sub-classes of tannins found in wine but they all share structural heterogeneity within each sub-class, with varied polymer composition, configuration and length.

Numerous methodologies exist for the quantification of tannins, however, protein precipitation using bovine serum albumin has proved itself useful due to its strong correlation to the sensory perception of astringency and the basic instruments required for the method. Though the method can yield valuable insights into tannin composition, it cannot be automated easily and necessitates well-trained personnel.

The study aims to address the issue of resilience to climate change in viticulture through the adoption of the expert knowledge elicitation (EKE) approach.

Purpose of this research is to quantitatively assess the mineral component of vineyard soils, with particular attention to the mineralogical analysis of clays, which represent an element of high importance in the vineyard culture as well as in general agriculture. An X-ray diffraction (XRD) / thermogravimetric (TG) multi-technique analytical approach was developed, tested on soil samples taken from vineyards around the world. This codified analytical procedure was necessary to obtain precise qualitative and quantitative mineralogical data, globally comparable to distinguish the geopedological identity of the vineyards. Soil samples from vineyards of various locations were analysed, in very different geological conditions. The bulk-rock quantitative phase analysis (QPA) was obtained by the Rietveld method while the detailed composition of the clay-sized fraction was determined by modelling of the oriented X-ray diffraction patterns. The research provided a precise classification of the mineral component of soils, distinguishing the mineral phases of the clays and the so-called mixed-layer clay minerals. We found that the content in mixed layers can be directly correlated with the water retention and the cation exchange capacity ​​of the soil, while the presence of other clayey minerals and phyllosilicates in this research did not affect this CEC parameter, which codes the fertility level of the soils. The study demonstrates that terroir, in particular soils formed in complex or very different geological conditions, can only be effectively interpreted by properly analysing its mineral phases, in particular the mixed-layer clay component. These are characteristic abiotic ecological indicators, which may have specific eco-physiological influences on the plant.

The designations of origin of the Loire Valley wine have been recognized according to customs and notoriety established over the centuries since the Middle Ages. There are four main production basins going up the Loire, from Nantes to the Sancerrois region: Nantes, Anjou-Saumur, Touraine and the vineyards of the Centre. In each of these basins, there is a wide range of appellations of origin which has been established according to a logic which may not seem obvious to the uninformed.