Geostatistical analysis of the vineyards in the canton of Geneva in relation to soil and climate

Soil and climate maps at the 1:10000 scales exist for more than 12’000 ha of Swiss vineyards. The use of these maps as consulting tools for growers remains difficult due to the complexity of the relationship between terroir and the large number of grape varieties planted. The current distribution of varieties and rootstocks is the result of a long optimization process. This study aims at analyzing the relationships between grape varieties, soil characteristics and climatic conditions.
The study was performed on the 1365 ha of Geneva’s vineyards with 3885 digitalized parcels. The 19 grape varieties planted on at least 5 ha were matched with the soil and potential radiation maps. The surface of each variety-soil combination and the mean radiation were calculated for each parcel.

The analysis showed that grape varieties were primarily planted according to meso-climatic conditions. Late ripening varieties, like Syrah or Merlot, were always planted on parcels receiving higher amounts of radiation than those planted with Pinot noir or Gamaret. Minimum radiation was calculated for each variety. Traditional grape varieties (e.g. Gamay or Chasselas) were planted in all meso-climates, indicating that the warmest plots were not judged to be too warm for early varieties. Regarding soil characteristics, early varieties were more present on BRUNISOL, which mainly represented flatter areas of the vineyards (10 % mean slope) and late varieties on steeper areas (mainly CALCOSOL with 16 % mean slope).
The present study revealed actual practices and criterions used by growers to make planting decisions. It might indicate minimum climatic and soil requirements for a given variety in the canton of Geneva. Continued monitoring may show the adjustments made by the growers to correct unsuccessful planting decisions. The analysis of these adjustments provides useful information for vineyard consultants.