Does sulfate addition to soil increase the solubilisation and the availability of cadmium for durum wheat?
Résumé
Cadmium (Cd) is a trace metal toxic to humans that naturally occurs in agricultural soils. Durum wheat naturally
accumulates more Cd in grains than other cereals, and can reach concentrations close to the regulatory limit of 0.18 mg
kg-1 set by European Union (EC 1323/2021). In literature, the addition of large amounts of sulfates (S-SO4) to soil was
shown to enhance the solubilisation and the availability of Cd for plants, due to the formation of Cd-SO4 complexes.
The main objective of our study was to assess if the availability of Cd for durum wheat was changed by S fertilization
of cereals, and, if yes, if it was due to sulfates or to the associated counter ions.
Two agricultural soils naturally contaminated with Cd were collected in the field: a clay limestone soil and a non-
calcareous loamy soil. The effect of two forms of S-SO4 commonly used as S fertilizers (K2SO4 and (NH4)2SO4), and
of their respective control (KNO3 and NH4NO3) were applied to soils samples in controlled conditions at agronomic
rates. After 1 and 21 days of incubation, total soluble Cd and its free ionic fraction in 0.005 M KNO 3 extract were
determined along with the pH and the concentration of soluble carbon and other main chemical elements.
In the non-calcareous soil, the solubility of Cd increased both with the S fertilizers and in the controls, suggesting that
it was not due to the formation of CdSO4 complexes but to ion exchange between Cd sorbed onto the solid phase and
the counter ions (NH4+ and K+) supplied with S fertilizers. In the limestone soil, the solubility of Cd was selectively
increased in the (NH4)2SO4 treatment for reasons yet to be determined. A modeling approach using the ORCHESTRA
model is underway to highlight the mechanisms of Cd solubilisation in both soils.
Domaines
AgronomieOrigine | Fichiers produits par l'(les) auteur(s) |
---|