Summary of risks from cadmium in agricultural soils
Chapter 6: Assessment of risk to land use flexibility
There are two main adverse impacts on land use flexibility which could occur from cadmium accumulation:
1) Cadmium accumulation in agricultural soils could affect the future ability to subdivide the land for residential or rural-residential purposes without some form of rehabilitation. In New Zealand, a substantial portion of new residential housing development takes place over agricultural (pastoral and horticultural) land, which is often moderately elevated in cadmium due to use of phosphate fertilisers. While such land is unlikely to pose any human health risks, it may exceed a guideline value for acceptable cadmium levels in soils, depending on the guideline value selected by a council following CLMG#2.
This problem would mostly affect those with land that had received ongoing applications of phosphate fertiliser (e.g. dairy), that was close to the perimeter of an urban area and who wished to subdivide their land into residential blocks.
2) If cadmium in agricultural soils built up to significant levels over time, this could affect the ability of landholders to grow certain types of agricultural products, due to the cadmium levels in these products exceeding food standards, or best-practice requirements set by overseas markets (such as EUREPGAP).
This problem could affect people wishing to convert from a land use which had required ongoing phosphate fertiliser application (e.g. dairy or pastoral) to growing a horticultural crop which was sensitive to cadmium levels in the soil. It could also affect those wishing to switch from growing fruit crops to vegetables, if the land had received significant phosphate application whilst growing fruit.
The two different land-use flexibility issues require different responses. The first type of risk stems from some uncertainty over how regional councils should best assess and approach the issue of cadmium, and other contaminants, in soils. It could be addressed through the development of a National Environmental Standard.
The second type of risk needs to be managed through improved monitoring of cadmium levels, providing information to farmers and growers, ensuring that the standards used to assess safe levels of cadmium in food are interpreted and applied in a consistent and science-based manner, and, where appropriate, on-farm management techniques such as deep-ploughing or liming to manage cadmium levels in soils.
Contact for Enquiries
MAF Information Services
Pastoral House
25 The Terrace
PO Box 2526
Wellington, NEW ZEALAND
Fax: +64 4 894 0721
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