Cadmium content of phosphate fertilizers used for tobacco production

Tobacco ( Nicotiana tabacum L.) leaves may accumulate relatively high levels of cadmium (Cd). The presence of cadmium in soils originates from both natural and anthropogenic sources. In particular, phosphate fertilizers can contain high Cd levels due to the presence of cadmium in the phosphate rock used for their manufacture. In order to investigate the Cd concentration in phosphate fertilizers used for tobacco production, fertilizers were sampled worldwide and analyzed for Cd and phosphorus. Concentrations ranged from 0.08 +/- 0.14 to 97.50 +/- 8.74 g Cd/t P2O5. In some cases, these levels could be explained by the phosphate rock origins. Some of the Cd contained in the fertilizer appeared bioavailable, as determined by diethylenetriaminepentaacetate (DTPA) extraction. Although the bioavailability of the Cd added through these sources to the tobacco plants in the field is not known, the use of fertilizers containing high Cd concentrations should be avoided to protect the soil from gradually accumulating this element and to avoid possible additional Cd presence in crops. Therefore, while several strategies may be followed to reduce the Cd concentration in tobacco leaves, the implementation of new agricultural practices such as the screening of the fertilizer source may also contribute to reducing further soil accumulation of Cd.