u/HiCookieJack

Found here: https://aulascienze.scuola.zanichelli.it/materie-scienze/scienze-della-terra-aule/degrado-suoli/

*edit

Just because I saw some valid arguments about the agricultural output of certain regions. As I understand this map is only relevant for the soil quality, not the productivity. Productivity seems to be influenced by a lot of other factors lots of you pointed out.

For those who want to read more on what these values mean:
https://en.wikipedia.org/wiki/Soil_quality