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New fertilizer SRM can help control heavy metal content

October 13, 2006

A new reference material developed by the National Institute of Standards and Technology (NIST) can help the agriculture industry and state regulators monitor the concentrations of several potentially hazardous heavy metal contaminants in fertilizers.

Modern multi-nutrient fertilizers produced for home and agricultural use are formulated from multiple sources to provide significant amount of nitrogen, phosphorus and potassium, the major plant nutrients, and lesser or even trace amounts of other nutrients needed by different crops, such as boron, calcium, iron and zinc.

Until relatively recently, fertilizers were tested and certified for their nutrient content, but little attention was paid to the possibility of heavy metal contaminants introduced by the mineral sources used to prepare the fertilizer. However, in response to incidents of heavy metal contamination of cropland, several states have enacted regulations in the past seven years that limit the amounts of some potentially hazardous non-nutritive elements in fertilizers. Several countries, including Japan, China, and Australia, and the European Union, also limit the amount of selected elements in fertilizers.

While fertilizer manufacturers and state regulatory authorities have needed to develop analytical methods to implement these regulations, until now there have been no certified reference materials available that they could use to validate the accuracy of their measurements. It can be difficult to measure accurately trace levels of some metals in a chemically complex mixture like fertilizer.

NIST's Standard Reference Material, SRM 695, "Trace Elements in Multi-Nutrient Fertilizer," was developed in collaboration with members of the Association of American Plant Food Control Officials (AAPFCO) and The Fertilizer Institute (TFI) to help meet this need. SRM 695 is a typical multi-nutrient fertilizer certified for the content of both major elements and trace elements, including calcium, iron, magnesium, manganese, sodium, potassium, zinc, arsenic cadmium, chromium, cobalt, copper, mercury, molybdenum, nickel, lead and vanadium. Additional reference values are provided for aluminum, boron, nitrogen, phosphorous and selenium.

National Institute of Standards and Technology (NIST)