Effects of different potassium fertilizers on cadmium uptake by three crops

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 SO₄^2- 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.