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) is a toxic, heavy metal naturally found in Saskatchewan soils. Cd accumulation in flax is a major issue deemed to affect flax markets after the European Union in 2021 imposed a new maximum Cd limit of 0.5 parts per million (ppm) for imported linseed. This project evaluated the efficacy of zinc and gypsum application at seeding in reducing Cd accumulation in harvested flaxseed. A high Cd-accumulating variety, Prairie Thunder, was used. The experiment was set up as randomized complete block design at four sites – Indian Head, Yorkton, Scott, and Redvers. Untreated control was compared with treatments of zinc and gypsum each at 1X, 0.5X, and 2X rate. Soil and MAP fertilizer samples were collected prior to seeding to establish a baseline level of Cd at each site. During the growing season, data were collected on plant emergence and height to evaluate toxicity effects of treatments, and harvested seed was weighed and analyzed for seed Cd content. Soil and MAP Cd levels varied considerably between sites, and the amount of Cd inadvertently added with MAP application varied from 0.003 lb/ac at Yorkton and Scott to 0.006 lb/ac at Indian Head. Soil Cd levels varied from negligible (<0.1 ppm) at Redvers to 0.5 ppm at Yorkton. In evaluation of plant traits, none of the treatments were found to have toxicity effects on flax as emergence, height, and yield did not vary significantly between treatments at any of the sites. In comparing the effects of treatments on Cd accumulation in harvested flaxseed, Redvers was the only site that had seed Cd levels for all treatments under the MRL of 0.5 ppm. Significant differences between treatments were only observed at Yorkton, where zinc applied at 2X rate resulted in a significantly reduced seed Cd content compared to zinc applied at 1X rate and gypsum applied at 2X rate. None of the other treatments generated statistically significant results, and none of the treatments at any site led to a significant reduction in seed Cd level compared to untreated control, even at ECRF where treatment effects were detected for this variable. So far, the efficacy of these treatments was questionable and there is need to test in another field season.
Grower Benefits
Soil and MAP fertilizer samples analyzed for cadmium content confirmed that cadmium levels vary drastically across Saskatchewan soils and in different samples of MAP. These differences in cadmium levels in soil and MAP fertilizer were reflected in how cadmium accumulated in harvested flaxseed at different sites, several of which had flax Cd levels higher than the MRL of 0.5 ppm set by the EU.
Treatment of flax with varying rates of zinc and gypsum showed no statistically significant difference on plant establishment and plant height between treatments at any site. Treatment effect on yield was also not statistically significant. Thus, none of the treatments in this trial led to toxicity effects in plants or significant reduction in yield during the growing season.
The effect of treatments on cadmium content in harvested flaxseed was mixed and statistically insignificant at all sites except ECRF. ECRF had some indication of treatment responses, and three treatments − zinc applied at 0.5X and 2X rate, and gypsum applied at 1X rate – had cadmium levels under the MRL of 0.5 ppm set by the EU. None of the treatments, however, had Cd levels that were significantly lower than the control at this site. SERF was the only site that had cadmium levels below 0.5 ppm for all treatments. None of the treatments at any site were effective at significantly reducing seed cadmium content compared to untreated control, thus making the treatments less economically worthwhile.
Reduction of Cadmium Uptake in Flax Using Agronomic Strategies (Year 2) – SK Oilseeds
