Sulfur fertilization slightly reduced grain cadmium concentration in a high cadmium durum wheat cultivar grown in the field

Cadmium (Cd) is a toxic element naturally present in the soil and high levels of Cd may accumulate in durum wheat grains, thereby threatening food safety. In the literature, sulfur (S) fertilization has been shown to reduce Cd translocation from roots to shoots in polluted soils. Therefore, we tested if S fertilization could also reduce grain Cd in field-grown durum wheat. One high and one low Cd accumulating cultivar of durum wheat were grown in the field in a soil moderately contaminated by Cd and fertilized with 0, 30 or 70 kg SO 3 ha −1 . The effect of N fertilization on plant growth and on grain Cd was also tested in the high Cd cultivar fertilized with 30 kg SO 3 ha −1 . S fertilization reduced the concentration of Cd in the grain of the high Cd cultivar by 18 % with no effect on the Cd extracted from the soil by 1 M NH 4 NO 3 . S neither significantly increased root Cd nor decreased shoot Cd, suggesting there was no effect on the root-to-shoot translocation of Cd. The number of kernels per head, increased by S fertilization, was negatively correlated with grain Cd concentrations, suggesting a dilution effect where Cd allocated to the spike was distributed across a greater number of kernels due to increased floret fertility. N fertilization increased grain Cd, particularly between 11.5 % and 14 % protein, at a linear rate of 0.029 mg Cd kg −1 and per percentage increase in protein. Based on our work, S fertilization is probably not a strong lever to limit the grain contamination in soils containing low concentrations of Cd. By contrast, the number of kernels per head could perhaps be maximized on Cd-contaminated plots. Our results show that limiting grain Cd can be achieved by growing low accumulator cultivars and by paying attention to N fertilization. • S × Cd interaction in durum wheat investigated at field scale. • S fertilization slightly decreased grain Cd concentration in the high Cd cultivar. • S fertilization increased floret fertility and thus Cd dilution in wheat grains. • No evidence of enhanced sequestration of Cd in roots induced by S fertilization. • N fertilization enhanced Cd accumulation in durum wheat grains.