From soil to tuber: cadmium uptake by potato plants and remediation mechanisms

High levels of geogenic soil cadmium (Cd) concentration have been reported in certain regions of the world, potentially increasing the risk of Cd concentrations in edible parts of agronomic crops, such as potatoes, exceeding their maximum allowable level of 0.1 mg Cd kg (fresh weight, FW)-1 set by various jurisdictions globally. Ireland has strong historical and cultural ties to potato cultivation, and potato-based foods are a significant dietary preference for its population. Consequently, the elevated Cd concentrations in Irish soils pose a substantial risk of excessive Cd exposure through potato consumption. Due to the geogenic origin of Ireland’s Cd problem, rather than anthropogenic inputs, nationwide research in Ireland has focused on soil amendments and breeding low-Cd potato cultivars. In previous field trials conducted by Teagasc, the agriculture and food development authority of Ireland, various soil organic amendments were selected and tested for their efficacy in reducing Cd content in potatoes and carrots. Results showed that, when applied at their highest rates, spent mushroom compost (SMC), poultry manure, and farmyard manure reduced tuber Cd concentrations by up to 40% relative to tubers grown in unamended soil. However, no single amendment consistently and significantly reduced tuber Cd across all tested soils. Therefore, a systematic understanding of the factors influencing Cd transfer from soil to potato tubers, as well as the mechanisms underlying the ameliorative effects of soil amendments, is essential. In this thesis, I traced the transfer of Cd from soil to potato tubers to study its uptake mechanisms and to evaluate the effectiveness of several soil amendments in reducing tuber Cd concentration, with a primary focus on soil geochemical processes. This thesis consists of four main chapters (Chapters 2-5) and a general discussion (Chapter 6).