Soil – farming system – food – health: Effect of conventional and organic fertilizers on heavy metal (Cd, Cr, Cu, Ni, Pb, Zn) content in semolina samples

Durum wheat (Triticum turgidum L. var. durum) is an important cereal crop extensively cultivated in Mediterranean areas, whose grain is predominantly used for pasta making.Ten durum wheat cultivars were cultivated during two consecutive years in the same area following both conventional and organic farming systems (CFS and OFS, respectively). The content of six heavy metals (i.e., Cd, Cr, Cu, Ni, Pb, and Zn) in soil and semolina samples from 10 different wheat cultivars was assessed, and the effect of conventional and organic fertilizers on these heavy metal contents evaluated. Although significantly higher heavy metal input to soil was provided by adding the organic fertilizer, semolina samples obtained from the cultivars grown in CFS were richer in Cd (82 μg kg−1vs. 18 μg kg−1), Cr (182 μg kg−1vs. 50 μg kg−1), and Cu (6.6 μg kg−1vs. 5.8 μg kg−1), thus suggesting a potential for the organic system to reduce the amount of these elements in the soil solution, to limit their availability and uptake by plants, and to influence their translocation processes to grains. On the other hand, semolina samples obtained from OFS showed higher concentrations of Ni (295 μg kg−1vs. 166 μg kg−1), Pb (94 μg kg−1vs. 82 μg kg−1), and Zn (13.6 mg kg−1vs. 10.8 mg kg−1) with respect to those obtained from CFS. These differences in heavy metal content among semolina samples obtained from OFS and CFS were also clearly highlighted by the Principal Component Analysis that showed, according to bulk results, the opportunity of encouraging/discouraging some cultivars in relation to the adopted farming system and to the kind of metals to be preferentially accumulated or depleted.