A phone call from a Saskatchewan farmer helps underline the importance of research into the cadmium content of grains and oilseeds.
The farmer has called a research scientist at Brandon, Man., to ask about cadmium content in flax. He wants to export the crop to Europe.
Cynthia Grant, a scientist at Agriculture Canada’s Brandon Research Centre, refers the query to someone who knows the issue.
Grant is among those leading the effort to reduce the cadmium content of Canadian crops. She’s passionate about that effort, concerned that cadmium levels could one day jeopardize Canadian grain exports.
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Cadmium, a heavy metal that can prove toxic if consumed in high doses, occurs naturally in the soil. It can also be added to the soil through fertilizer, manure and sewage sludge.
The international community has not yet set a global standard for acceptable cadmium levels in crops such as durum and flax destined for human consumption. However, the topic has been under review.
Rather than waiting for an international standard to be set, Canada has begun studying cadmium levels in its crops and exploring ways to curb those levels, if necessary.
The Canadian Wheat Board has not turned a blind eye to the issue. One of the crops that accumulates cadmium in its seed more readily than others is durum wheat. Canada and the United States produce more than 90 percent of the durum traded globally.
“Internationally, there is some concern, so therefore we need to be concerned too,” said Graham Worden, the CWB’s senior manager of technical services, market development department. “We’re not taking it lightly by any means.”
The Canadian Grain Commission said the presence of cadmium in crops such as durum is not a major trade issue now. However, there is some pressure on flax exports destined for food use, said the commission’s Tom Nowicki.
“We see a lot of customers coming forward with demands for safety assurance with regards to cadmium and flax.”
In Canada, the Canadian Food Inspection Agency oversees standards for contaminant metals, including cadmium. Those standards spell out acceptable limits for cumulative metal additions to the soil, said Linda Webster of the agency’s fertilizer section. One of the concerns is limiting the amount of heavy metals that accumulate in the soil over decades and centuries.
“Right now, we don’t have any evidence to suggest that our standards aren’t strict enough,” Webster said.
Through many years of research, Canada has learned much about what adds to cadmium levels in crops. Grant said there are several things farmers can do if concerned about cadmium in crops such as durum, flax and sunflowers.
Site selection is important, she said. If a field is known to have high levels of available cadmium, avoid seeding a crop destined for human consumption and is known for its uptake of cadmium into the edible parts.
As well, saline soils tend to enhance the uptake of cadmium, especially in areas of chloride-based salinity.
Grant cautions against overfertilizing, since some fertilizers, including nitrogen, tend to increase cadmium concentrations in cereal crops. Phosphorus does not appear to have significant effect on cadmium uptake, while zinc applications can either increase or decrease cadmium levels in crops.
Grant encourages farmers to set target yields and to fertilize accordingly. Low-cadmium cultivars are also being developed in Canada. Some of those varieties are already available.
Further research will help define what conditions add to the cadmium uptake of crops. Grant listed some factors that warrant a closer look: How soil types influence cadmium levels in crops; what tillage practices can lessen the amount of cadmium uptake; what role crop rotations play in the equation; and more review of fertilizing practices.
Research will also be done on the weather and how it affects cadmium uptake, Grant said.
“We’re looking at water in particular because water is life on the Prairies.”
