Aluminium and Silica Relationships in Growth Failure Areas

In 1962 an investigation was conducted to measure the reduction in hydrogen ion concentration of a weak acid (0.02N H,SO,) after it had been in contact with different soils. The acid-soil mixture was shaken, filtered and an aliquot titrated against 0.02N NaOH to neutrality. Of some 2,000 soils treated in this way, four were characterised by the formation of a clear gelatinous precipitate (considered to be some con~pound of Al) when the solutions were rendered alkaline. Subsequently they were found to belong to the Inanda soil series, and all were associated with growth failure areas. With the recent extension of cane cultivation into the Natal midlands, the likelihood of cane being grown on soils of the Clovelly series has increased. The fact that these soils are also high in A1 (Skeen and Sumner 1965) increases the urgency of an investigation into the relationship between soil soluble A1 and cane growth.