Silicon Calcium Fertilizer Application and Foliar Spraying with Silicon Fertilizer Decreases Cadmium Uptake and Translocation in Rice Grown in Polluted Soil

Rice cultivated in Cd-polluted acidic paddy soil poses important health risks in China. Decreasing Cd accumulation in rice is important for food safety and human health. Early rice cultivar ZY-819 and late rice cultivar XWX-13 with low Cd-accumulation potentials, and early rice cultivar LY-996 and late rice cultivar YZX with high Cd-accumulation potentials, were grown in mildly polluted double-cropping paddy fields (Cd content 0.3–0.6 mg kg−1). The effects of adding biochar (10 t ha−2), lime (1500 kg ha−2), and silicon–calcium fertilizer (SC; 2250 kg ha−2) and foliar spraying with silicon fertilizer solution (Si; 1500 g ha−2) on Cd uptake and transport in rice, were assessed in plot experiments. The soil amendments and foliar spraying decreased the Cd content of brown rice from the high Cd-accumulation potential cultivars. The soil amendments decreased the Cd content of LY-996 and YZX brown rice by 25.24–32.40% and 32.99–44.16%, respectively, and SC decreased the Cd content most. Foliar spraying with Si decreased the Cd content of LY-996 and YZC brown rice by 23.79% and 26.40%, respectively. When soil amendments and foliar spraying were combined, the Cd content of brown rice was decreased most by the SC–Si treatment. Compared with the control, the SC–Si treatment decreased the Cd content of LY-996, ZY-819, YZX, and XWX-13 brown rice by 45.63%, 35.67%, 52.79%, and 32.03%, respectively. Soil amendments can effectively decrease Cd uptake by rice roots and Cd migration from roots to shoots. Compared with the control, the soil amendments increased the soil pH and decreased Cd availability. The strongest effects were for the lime and SC treatments. Foliar spraying with Si can effectively decrease Cd translocation through stems and leaves to brown rice. Applying SC fertilizer and foliar spraying with Si is the best method for decreasing the Cd content of rice grown in mildly Cd-polluted paddy fields.