ABSTRACT
Aluminum (Al) is the most common metal in the Earth’s crust (8.2% by weight), the main Al-containing primary minerals being feldspars and micas, with a median Al concentration in soils of 7.2% (0.07%–30%) (Sparks, 2003). Only two elements, both nonmetals, have higher median concentrations in soils, O (46%) and Si (28%). By way of contrast, the median concentrations of the major basic metals are much lower-with 4.2% Ca, 2.3% Mg, 2.1% K, and 2.4% Na (Lide, 2007). The four major basic cations are essential for plant growth, and some studies have shown Al to promote plant growth. However, no benecial actions of Al in plant metabolism have been demonstrated.
