From which soil metal fractions Fe, Mn, Zn and Cu are taken up by olive trees (Olea europaea L., cv. 'Chondrolia Chalkidikis') in organic groves?

Principal component analysis of soil metal fractions in different depths suggested covariations with soil properties in organic olive groves. This graph demonstrates that the accumulation of organic matter in surface soils (0-20 cm) controls the bioavailability of Fe, Mn, Zn and Cu whether estimated on the basis of a single extraction (DTPA) or based on the labile fractions of a sequential extraction scheme.160