Cadmium: The Chatham Rise rock phosphate has been tested as having low rates of cadmium, which makes the product attractive from an environmental management perspective:
Cadmium Management Strategy for New Zealand
Ministry of Forestry and Agriculture has recently announced a strategy to manage cadmium levels in New Zealand soils.
Cadmium is a naturally occurring heavy metal that has been accumulating through the use of fertilisers derived from phosphate rock.
At current levels, cadmium does not pose any threat to human or animal health, but there are future risks if cadmium levels continue to rise.
The natural levels of cadmium in the soil range from 0 to 0.77mg/kg averaging 0.35mg/kg of soil.
The increase in soil cadmium levels in the last 10 years has been 5 micrograms /kg of soil
This is despite the industry voluntary cadmium limitation scheme audited by Fertmark.
The objective of the voluntary cadmium management strategy is to ensure that cadmium in rural production poses minimal risks to health, trade, land use flexibility and the environment over the next 100 years.
Four soil cadmium trigger values have been set. "a" 0 - 0.6mg/kg; "b" 1.0mg/kg; "c" 1.4mg/kg; "d" 1.8mg/kg.
Different cadmium soil management strategies have been developed including; using sources of P that do not contain cadmium; raising soil Ph; maintaining high soil organic levels; alleviating any soil zinc deficiencies; avoid acidifying fertilisers like CAN; avoid fertiliser blends that have high levels of chloride and using crop varieties with a lower cadmium uptake.
For more information contact Kevin Geddes, Executive Director, Fertiliser Quality Council. kgeddes@fedfarm.org.nz