Accumulation of cadmium and selected elements in flax seed grown on a calcareous soil

Seed of flax (Linum usitatissimum L.) grown on calcareous and neutral soils sometimes accumulates relatively high concentrations of Cd. The influence of a post-flowering application of NH₄NO₃ (115 mg N kg^-1), CdSO₄ (1 mg Cd kg^-1), FeEDDHA (2 mg Fe kg^-1), NaH₂PO₄ (120 mg P kg^-1) and ZnSO₄ (8 mg Zn kg^-1) on seed accumulation of Cd, Fe, N, Mn, P and Zn by flax grown on a Calciaquoll was studied in two experiments under greenhouse conditions. Seed yields were increased by the N and Zn treatments, and the N×Zn interaction was positive. Zinc deficiency delayed flowering and boll formation by up to 20 days and reduced seed size. In the absence of added Cd, seed accumulated up to 0.33 mg Cd kg^-1. This Cd accumulation was reduced by approximately 50 and 17% by added Zn and Fe, respectively, but was little affected by P fertilizer and post-flowering N stress. In the presence of added Cd, seed Cd exceeded 3.3 mg Cd kg^-1, and the antagonistic effects of Fe and Zn on seed Cd were absent. Seed N, P, Fe and Zn concentrations were increased on average by 10, 45, 31 and 97% by the N, P, Fe and Zn fertilizer treatments, respectively. FeEDDHA reduced seed Mn concentration by approximately 58%. However, seed Mn concentration was much less than that found in vegetative tissue at flowering. Soil-applied Zn may reduce seed Cd concentration in flax under field conditions, and may increase marketability of flax for food use.