Speciation and distribution of cadmium in soils of the Prairies
Most of the Cd in grain results from plant uptake from soils which could vary in Cd concentrations depending largely on the type of soil parent material. This project will compare paired pedons of cultivated and uncultivated soils in the agricultural regions of the Prairies for their cadmium levels, distribution within soil profiles and the phytoavailability of the Cd in these soils.
IPNI-1993-CAN-MB7
24 May 2001
Justification
- Export markets for Canadian durum, sunflower and edible flaxseed may be at risk due to high cadmium concentrations in the seed. The Canadian Grain Commission indicated that commercial composites of shipments of Canadian durum wheat had Cd levels which were slightly higher than those from Italy, Greece, Argentina and the United States. In 1992, Canadian production of durum wheat was a record high as reflected in our export increase to the United States. While the United States may have protested our marketing prices and practices through the Free Trade Agreement, it is unlikely that our own major markets would suffer drastically given that US durum appears to have similar problems with respect to cadmium in the grain. In fact, it appears likely that Canadian durum can become more competitive if you could hold out the promise that we are improving our breeding efforts and understanding the fertilizer-soil-plant aspects of the cadmium problem. While flax as a food ingredient seem to be limited to niche markets (e.g. German flax bread), this type of use could rapidly diminish if adverse publicity about relatively high levels of cadmium in flax should come about. The same is true for sunflower oil, for which Manitoba accounts for more than ninety percent of the Canadian production.
Most of the Cd in grain results from plant uptake from soils which could vary in Cd concentrations depending largely on the type of soil parent material. Notwithstanding differences in geology, the mobility and phytoavailability of cadmium in the soil largely depends on its chemical speciation which is further mediated by other pedological properties and reactions such as proportion of Cd on exchange sites (textural distribution), adsorption or co-precipitation onto oxides, association with organic macromolecules and chemical equilibrium between solution and solid phases. Thus, the ability of the soil to be a long-term sink may depend on microsite changes occurring in the soil which would vary with the rate and extent of weathering (i.e. soil type) and the management practices imposed on farmed lands. Further information is required on the interaction of availability. No systematic study based on soil genesis, morphology and mineralogical characteristics has been conducted. This project will compare paired pedons of cultivated and uncultivated soils in the agricultural regions of the Prairies for their cadmium levels, distribution within soil profiles and the phytoavailability of the Cd in these soils.