In acid soils of a more tropical environment containing smectites, as well as in highly buffered subtropical soils containing Al hydroxide interlayered smectite (HIS) or vermiculite (HIV), the values of exchangeable Al, extracted by KCl solution (Al-KCl), may be exceptionally high, but not always toxic to the crops. This “exchangeable” Al does not come solely from electrostatic sites. This study aimed to evaluate the relationship between the Al extracted from the soil by KCl and ammonium oxalate solutions, and clay […]