Heavy metal accumulation in a sandy soil and in pepper fruit following long-term application of organic amendments

Heavy metals are toxic and persistent pollutants that may be present in organic waste materials used as soil amendments. Following accumulation in amended soil, crop plants could assimilate these pollutants in sufficient concentrations to pose a threat to humans consumers. The Federal Clean Water Act and additional state regulations set minimum standards for heavy metals in organic amendments. Cumulative amounts of heavy metal pollutants that may be added to soils through amendments are regulated through national and state environmental protection agencies and the Federal Food and Drug Administration regulate maximum tolerances of heavy metal contaminants in food. The objective of the research was to study the effects of long-term organic amendment application on the accumulation of heavy metal pollutants in soil and subsequent contamination in pepper fruits. Organic amendments were applied yearly to replicate large plots during 1996 to 2000. Controls received no amendments. Different organic amendments were applied every year to simulate grower organic amendment availability throughout long-term application. Although higher levels of extractable Cd, Cu, Ni, Pb, and Zn were observed from amended soils during 1996 to 2000, all were within acceptable levels. Furthermore, no accumulation of Cd, Cu, Pb, and Ni was observed in pepper fruit. Therefore, long-term application of organic amendments made from waste materials with pollutant content below maximum acceptable levels under state and federal regulations should be suitable for vegetable production.