As organically produced food attains higher prices in the marketplace, there is concern over mislabeling of conventionally grown crops as ‘organic’.

Martina Šturm and co-workers, Jožef Stefan Institute, Slovenia, have shown that application of single treatments of synthetic fertilizer can be traced in lettuces by using elemental analysis and mass spectrometry to measure the nitrogen isotopic fingerprint (δ¹⁵N) values of lettuces.

δ¹⁵N values of plants receiving organic fertilizer were significantly higher compared with the treatments with synthetic N, reflecting the higher δ¹⁵N value of organic fertilizer. If a lettuce was treated with a single application of fertilizer, it was possible to determine whether this was synthetic or organic. If fertilizer is applied in small amounts over a longer time period, it becomes harder to distinguish the source.

• Can δ¹⁵N in lettuce tissues reveal the use of synthetic nitrogen fertiliser in organic production?
  M. Šturm, N. Kacjan-Maršić, S. Lojen,
  J. Sci. Food Agric. 2010, 90.
  DOI: 10.1002/jsfa.4179