From Soil to Tuber: Cadmium Uptake by Potato Plants and Remediation Mechanisms

Elevated geogenic cadmium (Cd) levels in Irish soils pose a risk of exceeding food safety limits in potatoes. In this thesis, I traced the pathway of Cd from soil to potato tubers to investigate its uptake mechanisms and evaluate the effectiveness of several soil amendments in reducing tuber Cd concentrations, with a primary focus on soil geochemical processes. This was achieved through a combination of laboratory and glasshouse experiments, as well as a geochemical multi-surface modelling (MSM) approach.
Hydroponic experiments showed that Cd uptake by roots is limited by its diffusive transport from the soil solution to the root surface. A pot experiment assessed the effects of lime, zinc (Zn), and spent mushroom compost (SMC) on reducing tuber Cd concentrations. With the help of the MSM, it was demonstrated that soil pH and organic matter are key controls on Cd availability, and that both Cd intensity and replenishment capacity govern plant uptake. Lime reduced Cd availability but unexpectedly increased tuber Cd, likely due to plant physiological responses. Zn had minor effects, whereas SMC most effectively reduced tuber Cd (up to 47%) and increased yield.