Since the moment I've post my question, I did some research and found some databases that nearly fulfill my needs.
1) European Soil Database (Europe-28 + Turkey + neighborhood countries)
The webpages of the European Soil Data Centre have indeed interesting database, such as the European Soil Database, available here. Understanding the database takes some times: here are my notes for anyone interested for using the database:
- A form must be filled in and the data can then be downloaded after receiving an email. The raw database is contained in a folder (named soilDB_shapefiles_and_attributes). A simplified version, with a shapefile with the joins already performed is available in th e folder ESDB. This shapefile
contains about 40 fields.
- Table 2 of PTRDB_Metadata.doc provides explanations about how some fields were computed using pedotransfert functions)
- SGDBE_attricod.doc provides most of explanations and classes of fields.
- shp_sgdbe_and_ptrdb_attributes.xls provides the names of the fields.
2) FAO Digital Soil World Map (Global)
A zip file was downloaded (from here: http://www.fao.org/geonetwork/srv/en/main.home?uuid=446ed430-8383-11db-b9b2-000d939bc5d8) with a shp of the digital soil map of the world. But the resolution of this vector data is bad, with very smooth polygons. The EU soil map has much more classes and a finer resolution.
3) Harmonized World Soil Database (Global)
4) Lastly, there is this excellent page of David Rossiter that references dozens of soil database across the world: http://www.css.cornell.edu/faculty/dgr2/research/sgdb/sgdb.html + this page that references some other resources: