Exchangeable Aluminium as a Basis for Lime Requirement Determinations in Acid Forest Soils

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Abstract
Samples from the B horizon of 23 podzolic forest soils were incubated with CaCO3 in amounts corresponding to aluminium extractable in 1 M KCl (readily available aluminium, AlKCl) and aluminium extractable in 0.5 M CuCl2 (readily plus nonreadily available aluminium, AlCuCl2 ) pH and the concentration of aluminium and calcium were determined in H2O extracts. The average initial pH value, aluminium concentration and molar Ca/Al ratio were 4.2±0.2 (X±SD), 55.9±32.9 micromole·liter-1 and 0.9±1.6 respectively. After the lime treatment pH increased to 5.5±0.3 (liming corresponding to AlKCl), and 6.4±0.5 (liming corresponding to AlCuCl2 ). The aluminium concentration was 25.5±11.6 micromole·liter-1 and 22.4±10.9 micromole·liter-1 respectively. The corresponding Ca/Al ratio was 4.8±3.4 and 30±34. It was concluded that the aluminium toxicity, if any, would be completely eliminated after a lime treatment corresponding to AlKCl. Furthermore pH 5.5 is within the pH range aimed at in ongoing forest liming experiments.
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