Table 1.

Iron content (g kg⁻¹ soil) of studied soils.

Analysis	Granitic	Methamorphic	Volcanic–allophanic
Total Fea	10.4 ± 0.3	11.8 ± 0.5	8.4 ± 0.5
Fe2+	2.3 ± 0.5	5.8 ± 0.4	3.2 ± 0.2
Fe3+	8.1 ± 0.3	6.0 ± 0.5	5.2 ± 0.3
Fedb	8.2 ± 0.1	3.1 ± 0.0	1.2 ± 0.1
Feoc	6.1 ± 0.2	2.3 ± 0.3	1.4 ± 0.1
Fepd	0.7 ± 0.02	0.9 ± 0.04	0.7 ± 0.1
Fece	2.0 ± 0.2	3.7 ± 0.2	3.8 ± 0.2

^aSum of Fe²⁺ and Fe³⁺

^bDithionite extractable iron.

^cOxalate extractable iron.

^dPyrophosphate extractable iron.

^eCrystalline iron Fe³⁺ minus Fe_o.