I have read in environmental science textbooks that aluminum can acidify soil, whereas metals such as sodium, calcium, magnesium, and potassium can alkalinize soils. I understand that Al3+ can hydrolyze water to form 3H+ and lower pH.
Why are alkali and alkaline earth metals described as alkalinizing soils? I understand that the neutral elemental forms of these metals (alkali, alkaline earth) react with water to form OH-, but the prevailing cation-form is much less reactive, except that it might precipitate with OH- from water self-ionization, and shift the equilibrium towards more H+.
I also know that some of these cations are commonly found in minerals with carbonate and silicate that can lead to OH-, but this seems to driven by the counter-ion, not the metal cation.