What is the best soil for Sangiovese quality wine?

Sangiovese is one of the main cultivar in the Italian ampelographic outline and it occupies more than 60% of total vineyard surface in the Tuscany region. It is also well known that the environmental variability causes an important influence over the viticultural and oenological results of Sangiovese, which does not have strict genetic control over the vegetal-productive behaviour.
The aim of this work was to single out the best soil characteristics for Sangiovese quality, on the basis of the vine performance of Sangiovese (VPS). For this purpose, a matching table, considering eight viticultural parameters, was utilized. The matching table permitted to classify the selected parameters into three classes of decreasing vine performance. A set of 79 experimental plots, sited on 47 farms, were utilized during a time span varying from two to five years (1989-1992; 1993-1994; 1997-2000; 2002-2007 and 2008-2009). Two datasets were created. One considering all the invariant soil and topography characteristics of the plots. The second, storing the year-depended variables. The data were submitted to principal component analysis (PCA) to highlight those invariant and year-depended climate and pedoclimate variables which were significantly correlated with the average values of the VPS of each vineyard. Discriminant Analysis was employed to identify the most significant variables and their discriminating power on VPS.
The results highlighted that invariant site characteristics are the most discriminant at the province level, while climate and pedoclimate show their influence on VPS at more detailed scales. At the province level, VPS is significantly influenced by rock fragments, stoniness, available water capacity (AWC), and elevation. The ideal soil for Sangiovese in the province of Siena is placed between 315 and 335 m asl, has an AWC ranging from 110 and 120 mm, shows a limited surficial stoniness of about 8-10%, and it is rather skeletal (rock fragments content 12-16%).
These results can be used in land evaluation and vine zoning, in particular, for the selection of the best crus of the province, they may help the choice of land for a new vine planting, but they might be also used in pedotechnique, that is, in the creation of vineyard soils by means of earth movements.