Cadmium contamination of agricultural soils has aroused worldwide concern because of the threats posed to human health through accumulation in food chains. A greenhouse pot experiment was conducted with in situ Cd-contaminated soil to study the influence of different potassium fertilizers (KCl, K2SO4, and KNO3) on Cd accumulation in rice, wheat, and pak choi as well as the NH4NO3-extractable Cd (NEX-Cd) content in soils. In our study, rice and wheat biomass increased in the presence of K fertilizers, whereas pak choi biomass remained stable. Moreover, our experiment demonstrated that Cl- increased Cd uptake by crops more effectively than SO42- or NO3-. The KCl treatments increased the Cd content of all three crops; as the KCl dose was increased, the Cd content of rice grains, wheat grains, and pak choi shoots increased by 10.8-192.8%, 17.1-67.7%, and 15.1-40.4%, respectively. The KNO3 treatment also increased the Cd content of all three crops; however, the K2SO4 treatment only slightly increased the Cd content of wheat and pak choi and greatly decreased the Cd content of rice. In addition, both of the NEX-Cd content of wheat soil and pak choi soil were much higher than that of rice paddy soil. The KCl treatment resulted in a significant increase in the NEX-Cd content of rice paddy soil, but there were no significant differences in the NEX-Cd content of wheat soil or pak choi soil, regardless of which types or doses of K fertilizers were supplied. Based on these results, when K fertilizers are applied to Cd-contaminated soils, both types and doses should be carefully considered to mitigate Cd accumulation in crops, especially the edible part.
Keywords: Anion; Bioavailability; Cadmium; Potassium fertilizers; Soil-plant system.