2007 Annual Report
1a.Objectives (from AD-416)
Summarize literature on potential risk to consumers of cadmium applied to land as part of phosphate fertilizers. Includes availability to plants over time, transfer to edible plant parts over time, and bioavailability to animals of Cd in crops grown on fertilized soils, and the exclusion of cadmium from livestock products. Consider wide literature on cadmium in the agricultural environment, and nature of phosphate products in the marketplace. Characterize levels of Cd or Cd:Zn which provide protection against adverse effects of cadmium in fertilizers. Interpret information in relation to proposed limits on cadmium in fertilizer products in the EU to support needs of The Fertilizer Institute.
1b.Approach (from AD-416)
Conduct literature review to identify appropriate and inappropriate methods to assess potential food-chain transfer and risk from cadmium in phosphate fertilizer products. Studies which tested cadmium salts are likely to over-predict risk because phosphate reactions with iron in soils increases specific adsorption of cadmium, and zinc which accompanies cadmium in phosphate fertilizers can inhibit cadmium uptake and bioavailability. Interpret potential risks from cadmium in phosphates with respect to new paradigm for cadmium risk due to zinc, iron and calcium deficiency in subsistence rice consumers. Contrast soil cadmium potential risks from different cadmium sources including fertilizers, cadmium aerosol emissions, manures, biosolids, limestone, etc. Evaluate proposed scientific basis for EU limits on cadmium in phosphates and the database for the draft regulations. Summarize information which could improve the EU risk assessment.
3.Progress Report
This report documents research conducted under a reimbursable agreement between ARS and The Fertilizer Institute. Additional details of research can be found in the report for the parent project 1265-12000-037-00D, Risk Assessment and Remediation of Soil and Amendment Trace Elements. Progress was made on publishing three manuscripts reporting parts of the work, and a detailed review paper is still being prepared for a peer-reviewed journal to summarize the process of risk assessment for Cd in fertilizer products, and alternatives for reducing potential risks. A test of using crumb rubber as a byproduct Zn fertilizer for growth of spinach and lettuce on Lockwood soil showed that addition of Zn sulfate could reduce Cd accumulation by 40% at 200 kg Zn/ha, but that the Zn in rubber was only slowly released and had no immediate effect on crop accumulation of Cd. Improved understanding of the many protections against transfer of excessive bioavailable Cd into diets is critical to evaluation of allowable Cd levels in all soil amendments, including phosphate fertilizers.
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