Objectives
This project was set up at four sites across Saskatchewan to demonstrate the efficacy of zinc and calcium fertilization for reducing cadmium levels in flaxseed. Varying rates of zinc sulphate and gypsum were applied and evaluated for their effect on cadmium accumulation in harvested flaxseed. Toxicity effect on plants during the growing season was also assessed. Lastly, an economic analysis was done to compare the economic feasibility of products.
Project Description
Cadmium (Cd) accumulation in flax is a concern for Saskatchewan producers after the European Union established a limit of 0.5 ppm of Cd for imported flaxseed in 2021. While Cd is naturally present in SK soils, more is added through the application of Monoammonium Phosphate (MAP) fertilizer contaminated with Cd from its parent rock. This demonstration intended to evaluate the efficacy of zinc and calcium fertilization in reducing Cd levels in flax. The demonstration was established at four SK Agri-ARM sites – WARC (Scott), ECRF (Yorkton), IHARF (Indian Head), and SERF (Redvers). Seven treatments were evaluated: 1) Untreated control, 2) Zn at 2.5 kg/ha, 3) Zn at 1.25 kg/ha, 4) Zn at 5 kg/ha, 5) Gypsum at 107 kg/ha, 6) Gypsum at 53.5 kg/ha, and 7) Gypsum at 214 kg/ha. 2023 was the second year of the trial. Flax variety CDC Rowland was used and data on plant density, plant height, and yield were collected. Soil and MAP samples were collected in the beginning of the experiment and sent to the lab for Cd analysis along with harvested flaxseed from the trial. Results showed large variation in MAP Cd levels (ranging from 9-39 ppm), but soil Cd levels were found to be relatively low (<0.1-2 ppm) among all sites. None of the treatments of zinc or gypsum had a significant effect on any of the measured parameters at any site. Since seed Cd level and yield had no apparent improvement upon the application of treatments, they were deemed economically inefficient compared to the untreated control.
Grower Benefits
Despite all locations being drier and warmer than their long-term average, the trial was conducted successfully at all sites.
Soil samples analyzed for cadmium (Cd) content showed low Cd in all 4 sites, ranging from <0.1 ppm to 0.2 ppm. Cd levels were more varied in MAP fertilizer samples collected from each site and ranged from 9.1 ppm at WARC to 39 ppm at IHARF. While a causal relationship could not be established between MAP or soil Cd content and Cd content of harvested flaxseed, the location at Indian Head (IHARF), with the highest seed and MAP Cd content, produced flaxseed with highest Cd levels (averaging 0.7 ppm, 0.2 ppm higher than the MRL of 0.5 ppm set by the EU). Average Cd content of seed harvested at all other sites was within the 0.5 ppm limit.
Individual site analysis showed no significant effect of any of the treatments of zinc or gypsum on plant density, height, yield, or seed Cd content. Treatment of flax with varying rates of zinc and gypsum produced similar results as the untreated control, thus rendering the treatments economically inefficient.
Compared to 2022, flax yield was significantly reduced at all sites in 2023. Cd levels in harvested flaxseed were also lower in 2023 at all sites except IHARF. However, none of the treatments of zinc or calcium in either year at any of the sites led to a significant reduction in seed Cd levels compared to the untreated control. Findings from two years of this project suggest that at the rates and formulations used in this project, the application of neither zinc nor calcium is effective at reducing Cd accumulation in medium-high to high Cd-accumulating flax varieties.
Reduction of Cadmium Uptake in Flax fact sheet
Year 1 – Reduction of Cadmium Uptake in Flax Using Agronomic Strategies – SK Oilseeds
