Nitrogen isotopic signature of vegetables from the Slovenian market and its suitability as an indicator of organic production

The aim of this study was to obtain preliminary data on δ¹⁵N values in organically and conventionally grown vegetables available on the Slovenian market to determine whether there are any characteristic differences in δ¹⁵N values, which could be used as a marker to differentiate between organically and conventionally grown vegetables, namely vegetables grown with synthetic or organic nitrogen fertilisers. Therefore, 14 different varieties of organically and conventionally grown vegetables were analysed. The results obtained show clear differences in mean δ¹⁵N values between organically and conventionally grown vegetables (up to 6.3\permil). However, due to overlapping results, it was not possible to differentiate between organically and conventionally grown counterparts in eight vegetable varieties, despite the differences in mean δ¹⁵N values. The results obtained indicate that the method has several limitations. Hence, δ¹⁵N could be a reliable indicator for organic production, but nevertheless, the conclusion has to be validated by background information.