Exploratory study on vineyards soil mapping by visible/near-infrared spectroscopy of grapevine leaves

This work demonstrates the possibility of discriminating vineyard soils through the non-destructive and in-situ visible/near infrared monitoring of leaves. A portable Vis/NIR spectrometer was applied for monitoring in-situ Vitis vinifera leaves in vineyards of two wine regions in Portugal in the maturation period. Leaves reflectance spectra of different grapevine varieties planted in different vineyard locations (distinct soil taxonomic types) were analyzed by principal component analysis and partial least squares discriminant analysis. Soil discriminant models based on leaves Vis/NIR spectra yielded for both vineyards approximately 95% correct soil taxonomic predictions. This methodology was then applied to monitor all plants within a 0.3 ha vineyard block in the Dão vineyard resulting in a highly detailed soil taxonomic map built exclusively from leaves Vis/NIR spectra. A comparison with the existing soil map proved that the NIR spectroscopy based estimation was very similar. Even though further studies are needed, namely in different maturation stages and other geographical regions, to ensure reliability of this technique, results in this work showed that it can be used as an additional auxiliary tool for obtaining vineyard soil maps. Its main advantages over pedological reference procedures are speed and cost efficiency analysis.