Foliar Spraying and Seed Soaking of Zinc Fertilizers Decreased Cadmium Accumulation in Cucumbers Grown in Cd-Contaminated Soils

Abstract

It is important to use proper agronomic management to reduce cadmium (Cd) accumulation in plants, ensuring food safety. To find the most effective agronomic approach, the effect of foliar spraying and seed soaking of zinc (Zn) fertilizers on Cd accumulation in cucumbers (Cucumis sativus L.) grown in two soil Cd levels (2 and 5 mg kg−1 Cd) with and without an immobilizing amendment (red mud, RM) was investigated in the present study. The results showed that the treatment of foliar Zn or seed Zn significantly decreased the Cd concentration in cucumber shoots by about 12–36% in Cd-contaminated soils without amendment. Combined with RM treatment, the foliar Zn treatment further decreased the Cd concentration in cucumber shoots by up to 48–66% in Cd-contaminated soils. There were significant negative correlations between Cd and Zn concentrations in shoots of cucumbers grown in soils treated with RM and foliar Zn. The results revealed that the cucumber seedlings treated with RM and foliar Zn had a higher capacity for limiting the transfer of Cd to aboveground tissues. The results also suggested that increasing seed Zn concentrations sufficiently might act as an efficient, economic, and practical method for decreasing Cd uptake in crops grown in mildly Cd-contaminated and Zn-deficient soils.