Federated Farmers: What you should know about cadmium in soils

Testing soil for Cd every five years as part of the soil testing regime for nutrient management is recommended. Photo / Paul Taylor

Understanding what your soil Cd levels are for your farm contributes valuable information that benefits all of New Zealand's primary producers.

Does your farm have a history of long-term phosphate fertiliser application?

If so, Tiered Fertiliser Management System is recommended if you want to understand how to manage soil cadmium (Cd) levels.

Testing soil for Cd every five years as part of the soil testing regime for nutrient management is a great place to start.

Your certified nutrient management adviser has a good understanding of this programme and can help provide advice on:

•The type of phosphate fertiliser used and getting the right application rate to minimise further Cd increases

•Pasture and crop management to minimise the uptake of soil cadmium, including maintaining optimum pH, alleviating crop zinc deficiencies, maintaining organic matter levels in cropping soils, and keeping good pasture covers to minimise soil ingestion by livestock.

Cd is a naturally occurring heavy metal present at trace levels in soils, worldwide.

While sources of cadmium include atmospheric deposition, industrial pollution and volcanic ash, cadmium accumulation in production soils is primarily due to the long-term application of phosphate fertilisers.

Phosphate rock, which is used to manufacture phosphate fertilisers critical to our primary production sectors, contains trace levels at varying amounts of naturally occurring Cd.

If, over a long period of time, Cd intake by animals and humans is high, it may accumulate in organs such as the kidneys and liver and can cause chronic toxicity problems.

Food produced on New Zealand soils meets food standards for cadmium and does not pose a risk of adverse health effects.

As a precaution, however, offal products from ruminants older than 30 months are excluded from human consumption to reduce the risk of exceeding food standards.

New Zealand has great soil resources and we need to ensure they stay that way. The active management of soil Cd levels is a critical part of future-proofing New Zealand's primary sector.

Understanding what your soil Cd levels are for your farm contributes valuable information that benefits all of New Zealand's primary producers.

The New Zealand Dairy Industry Award winners
Sharemilker/Equity Partner of the Year: Justin and Melissa Slattery.
New Zealand Farm Manager of the Year: James Foote.
New Zealand Dairy Trainee of the Year: James Davison.
Federated Farmers Leadership Award: Matt and Tracey Honeysett.

For more results, visit www.dairyindustryawards.co.nz

Ann Thompson is the executive director of the Fertiliser Quality Council.