Over the last decade, investigation of within-vineyard variability has benefitted from new tools embracing a new science called “precision farming” (PF). PF is based on the acquisition either of airborne multi-spectral images or data collected by proximal sensors which, once properly pre-processed, can yield vigor maps of the given areas characterized by a variable number of discrete levels of the Normalized Vegetation Index (NDVI).
The seminar has the following goals: a) provide a critical assessment how well-established physiological knowledge can fit and interact with the PF approach; b) evaluate the physiological background and validity of so called “variable rate technologies (VRT) which are, in turn, generated from PF. The correlation between NDVI, ground measured vigor and canopy function parameters will be discussed. A warning is given about the generalized use of the easy-to-measure pruning weight as an index of vine vigor since its correlation with vine capacity (i.e. leaf area) is sometimes loose as well as about the physiological meaning of “high vigor” map classes which, being always expressed on a relative basis, might correspond in reality to absolute low or moderate vigor.
Variable rate technologies work on the very clever principles of adding to the vineyard system input amounts calibrated towards vigor and productivity levels. VRT operations showed are leaf removal, mechanical harvesting, with a specifical emphasis on mineral fertilization. Especially when tackling fertilization, criticism is expressed on experimental layouts which, besides including VRT treatment, should also embrace controls at either no or constant dose of fertilizer. Moreover, in the case of N application, doses should also take into account specific vine needs according to phenological stages as well as yield decrease and quality worsening for luxury availability. VRT applied to mechanical harvesting is indeed fascinating as available solutions include a single harvest with separation in different tanks of grapes picked from low and high vigor zones or picking in two different steps according to the maturity level.
These tools are precious within a scenario where too fast and unbalanced ripening is increasingly frequent and a counteracting strategy depends upon timeliness and selectivity of the harvesting method.