Does organic farming reduce the content of Cd and certain other trace metals in plant foods ? A pilot study

The effect of organic cultivation systems on the level of Cd in wheat was studied in two consecutive harvests. Additionally, the concentrations of Cd, Pb, Cr and Zn were analysed in single harvests of rye, carrots and potatoes from different farming systems. Wheat and rye were obtained from controlled field trials using several conventional and ecological systems at two separate locations in Sweden. Potatoes and carrots were collected at private farms with conventional or ecological production. These farms were juxtapositioned and had similar soil properties. The levels of Cd in the wheat did not correlate with the cultivation system or the Cd content in the soil. Conventionally grown wheat from one field trial showed a significantly higher Cd level compared with ecologically grown wheat, while in the other field trial significantly lower Cd levels were detected in the conventionally grown wheat. No statistically significant differences in the concentrations of Cd, Pb, Cr or Zn in rye, carrots and potatoes were detected between the cultivation systems. The results indicate that organic farming, at least in the short term, does not necessarily result in reduced levels of Cd and other potentially harmful metals in foods of vegetable origin. Factors other than cultivation system may be of greater importance for the final concentration of Cd and other metals in plant foods.