Plant Sr Isotope Ratios As Affected by the Sr Isotope Ratio of the Soil and of the External Sr Inputs.

The 87 Sr/86 Sr ratio of a produce is generally linked with the soil geological features of the growing areas. This study aimed at assessing to which extent the addition of external Sr by agricultural practices, like irrigation and mineral nutrient supply, influences this relationship. In a first experiment, oat plants in two soils reflected the 87 Sr/86 Sr of the soil. However, this link was significantly altered at increasing levels of external Sr soil supplies. In a second experiment, apple trees transplanted in pots modified their original 87 Sr/86 Sr, which became progressively closer to the soil Sr isotope ratio. The addition of tap water and fertilizers, with different Sr isotopic signatures, slightly affected plant 87 Sr/86 Sr. Results confirm the potential of the 87 Sr/86 Sr ratio as a geographical tracer of agricultural commodities, but whenever the range of 87 Sr/86 Sr variability among soils from different geographical areas is narrow, the influence of external Sr-sources may smooth over these diversities.