Impacts of a Compound Amendment on Cd Immobilization, Enzyme Activities and Crop Uptake in Acidic Cd-Contaminated Paddy Soils

This study assessed the effectiveness of limestone-montmorillonite-rapeseed residue-Si fertilizer compound amendment on the bioavailability and crop uptake of cadmium (Cd) and enzyme activities in acidic paddy soils. Applying the compound amendment at ratios of 1%–3% increased soil pH by 0.1–1.9 units, decreased leaching ratios of soil Cd 4.0%–22%, and decreased exchangeable and carbonated Cd 42%–55% and 27%–49%, respectively. Organic matter-bound Cd increased 47%–62% (p < 0.05). Cadmium concentrations decreased in the roots, culms, leaves, and grains of rice grown in the Cd-contaminated soils by 37%–81%, 18%–73%, 29%–64% and 27%–63%, respectively, (p < 0.05). Catalase and urease activities increased 2.5%–63% and 3.9%–36%, (p < 0.05), respectively. Applying this compound amendment may significantly mitigate soil acidification and decrease the bioavailability and crop uptake of Cd in acidic Cd-contaminated paddy soils.