PLANT AVAILABILITY OF CADMIUM IN SOILS .1. EXTRACTABLE CADMIUM IN NEWLY AND LONG-TERM CULTIVATED SOILS

Effects of long-term use of phosphate fertilizers on extractable soil Cd in relation to its concentrations in plants were investigated. ''Paired'' soil samples were collected from newly and long-term cultivated fields and analyzed for Cd by extraction with NH4OAc, DTPA, NH4OAc-EDTA, NH4NO3, HCl and CaCl2. Plant samples were also collected and analyzed for Cd. Significant differences in extractable Cd by all the extractants except NH4NO3 were observed between the newly and long-term cultivated soils. The Cd concentrations in plants were not increased by the elevated extractable Cd. Although significant relationships were observed between plant Cd and extractable soil Cd, none of the extractants used alone gave a good assessment of plant-available Cd for all the samples used in this study.