Institute of Bio- und Geosciences (IBG)

Agrosphere (IBG-3)

Nutrient use efficiency

Stable isotope analysis of elements in their natural abundance can be used to identify and quantify sources in different environmental compartments. This approach is already widely used for tracing terrestrial O, C and N cycling (“traditional” stable isotopes), but can also be applied to other multi-isotope elements like the plant nutrients Mg, Fe and B (“non-traditional” stable isotopes). Due to the fact that the natural isotope composition variations of these non-traditional isotopes are very small, the determination of the isotope ratios requires mass spectrometric techniques with high precision and accuracy. In this subproject, we use multicollector-inductively coupled plasma-mass spectrometer (MC-ICP-MS) to determine isotope ratios of metalloids and metals in soil-plant systems.
The aim of the present subproject is to explore the natural variations of the isotope compositions of Mg, Fe, and B (expressed as δ²⁶Mg, δ⁵⁶Fe and δ¹¹B) along the soil depth profiles at the central field and the long-term sites investigated by the Soil3 consortium. Along with the isotope compositions determined in the plant tissues we want to assess the impact of different subsoil managements on plant nutrient uptake. Together with microcosm experiments to determine isotope fractionation factors during plant uptake, isotopic data from field trials will be evaluated to illustrate from which soil depth plants take up nutrients, how large the subsoil contribution to plant nutrition is and if this contribution changes with management practices. This unique approach will derive indicators of nutrient uptake from the subsoils for different cropping systems.