Effects of sulfur application on cadmium accumulation in brown rice under wheat-rice rotation

• Published in: Environmental pollution (1987) Vol. 287; p. 117601
• Main Authors: Huang, Lijuan, Hansen, Hans Chr Bruun, Yang, Xiaosong, Mu, Jing, Xie, Zijian, Li, Songyan, Wu, Guangmei, Hu, Zhengyi
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 15.10.2021
• Subjects: Cadmium; Cadmium - analysis; Crop Production; Oryza; Rice (Oryza sativa L.); Soil; Soil Pollutants - analysis; Soil pore water; Sulfur; Triticum; Wheat-rice rotation; Rice (Oryza sativa L.); Soil pore water; Cadmium; Wheat-rice rotation; Sulfur
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2021.117601

We investigated how sulfur (S) application prior to wheat cultivation under wheat-rice rotation influences the uptake of cadmium (Cd) in rice grown in low- and high-Cd soils. A pot experiment was conducted with four S levels (0, 30, 60, 120 mg S kg−1) and two Cd rates (low and high, 0.35 and 10.35 mg Cd kg−1) supplied to wheat. Part of the wheat straw was returned to the soil before planting rice, which was cultivated for 132 days. To explore the key mechanisms by which S application controlled Cd accumulation in brown rice, (1) soil pore water at the key growth stages was sampled, and dissolved Cd and S species concentrations were determined; (2) rice plant tissues (including iron plaque on the root surface) were sampled at maturity for Cd and S analysis. With increasing S level, Cd accumulation in brown rice peaked at 60 mg S kg−1, irrespective of soil Cd levels. For high-Cd soils, concentrations of Cd in brown rice increased by 57%, 228%, and 100% at 30, 60, and 120 mg S kg−1, respectively, compared with no S treatment. The increase in brown rice Cd by low S levels (0–60 mg kg−1) could be attributed to (1) the S-induced increase in soil pore water sulfate increasing the Cd influx into rice roots and (2) the S-induced increase in leaf S promoting Cd translocation into brown rice. However, brown rice Cd decreased at 120 mg S kg−1 due to (1) low Cd solubility at 120 mg S kg−1 and (2) root and leaf S uptake, which inhibited Cd uptake. Sulfur application to wheat crop increased the risk of Cd accumulation in brown rice. Thus, applying S-containing fertilizers to Cd-contaminated paddy soils is not recommended. [Display omitted] •Cadmium in brown rice is increased by sulfate application to cadmium contaminated soils.•Cadmium uptake is stimulated by sulfate in soil pore water while root iron plaque has no effect.•Sulfate application enhances cadmium translocation from leafs to brown rice.•Soil cadmium immobilization under anoxic conditions do not hinder increased cadmium uptake.