Food News

Plants absorb all minerals, including important trace elements, but also heavy metals, from the soil. Really?

In a joint research study conducted by the Helmholtz Centre for Environmental Research (UFZ) in Bad Lauchstädt (Saxony-Anhalt, Germany) and Duke University in Durham (North Carolina, USA), scientists investigated whether wheat plants absorb heavy metals primarily from the soil or from the fertilisers applied.

The wheat used for this study was grown on farmland that had not been fertilised since 1902. In particular, the wheat grains harvested over the last 20 years from this unique long-term experiment were examined using the strontium isotope signature method. The stable isotope pattern of ⁸⁷Sr and ⁸⁶Sr provides a typical ‘fingerprint’ for each soil. If this ‘fingerprint’ in the wheat grain is compared with that of the soil and both are identical, it can be concluded that the plant has absorbed the metal from the soil. If, on the other hand, this isotope ratio corresponds to that of the fertiliser used, this means that the metal came from the fertiliser.

It is known that the uptake of strontium and the heavy metal cadmium in plants is identical. In simple terms, this means that the origin of the heavy metal in the grain can also be determined. Analysis of the extensive data showed that the heavy metals originate from the fertiliser applied, especially from mineral fertilisers. However, soil composition also has an influence. In the experiment, the wheat was grown on fertile black soil. In sandy or acidic soils, it can be expected that the uptake of heavy metals by the plants will be even higher. Since permanent mineral fertilisation also causes soil acidification, measures to stabilise the pH value, such as liming the soil, are becoming increasingly important. In addition to undesirable heavy metals, the grain also absorbs valuable trace elements.

Further research is therefore needed to determine the extent to which targeted fertilisation can increase the trace element content without leading to an accumulation of heavy metals. The researchers therefore recommend combined fertilisation or the alternating application of mineral and organic fertilisers.

YOUR PLUS: The AGROLAB GROUP not only tests grain for mineral content, trace elements and heavy metal contamination, but also all fertilisers and the agricultural soils themselves. We provide farmers with precise GPS-supported fertiliser recommendations tailored to the respective crop.

Author: Dr Frank Mörsberger, AGROLAB GROUP