L1 /
9
CH3041
SOIL ACIDITY
Total acidity: titrate
with a base eg. Ca(OH)2. This acidity can be sub-divided into:
Total acidity -
Exchangeable = Non-exchangeable
• Exchangeable
acidity: bound H+ & Al3+
that is displaced into solution by 1.0M KCl.
that is displaced into solution by 1.0M KCl.
strong organic acids, exchangeable Al3+
• Non-exchangeable
acidity: not displaced
weak
organic acids, Al-hydroxy cations.
• The lime requirement is
the amount of CaCO3 needed to reduce the exchangeable plant toxic Al3+ to a safe level.
2-Al3+-clay + 3CaCO3 ® 2Al(OH)3 + 3Ca2+-clay
