2 Aluminum activation in soil Exchangeable Hydrogen is the main source of H+ at ph 6 and above Below ph 6 Aluminum is the main source of H+ due to dissociation of Al from clay minerals. Aluminum becomes more soluble at lower pH's A|3++H20---A(OH)++H Al(OH)+++H2O--->Al(OH)2++H+ Al(OH)++H20---> Al(OH)3+H+Exchangeable Hydrogen is the main source of H+ at pH 6 and above. Below pH 6 Aluminum is the main source of H+ due to dissociation of Al from clay minerals. Aluminum becomes more soluble at lower pH’s Al3+ + H20 ----> Al(OH)++ + H+ Al(OH)++ + H2O ---> Al(OH)2 + + H+ Al(OH)2 + + H20 ---> Al(OH)3 + H+ 2. Aluminum activation in soil