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@ARTICLE{Uhlig:909937,
      author       = {Uhlig, David and Wu, Bei and Berns, Anne E. and Amelung,
                      Wulf},
      title        = {{M}agnesium stable isotopes as a potential geochemical tool
                      in agronomy – {C}onstraints and opportunities},
      journal      = {Chemical geology},
      volume       = {611},
      issn         = {0009-2541},
      address      = {New York, NY [u.a.]},
      publisher    = {Elsevier},
      reportid     = {FZJ-2022-03531},
      pages        = {121114 -},
      year         = {2022},
      abstract     = {A sustainable use of soil resources is urgently required to
                      cope with the increasing demand for agricultural products
                      during climate change. To inspire farmers on new soil
                      cultivation methods like subsoil management requires not
                      only yield measurements but also nutrient use efficiency
                      measurements for which analytical tools are still missing.
                      Stable isotopes of the macronutrient magnesium (Mg) are a
                      potential novel subsoil management evaluation tool in
                      agronomy and soil/plant sciences because its isotope ratios
                      shift considerably during Mg uptake by crops. The
                      feasibility of Mg stable isotopes was first demonstrated
                      conceptually by simulating subsoil management on soils with
                      low, middle, and high inventories of bioavailable Mg and
                      crop plants typically cultivated in Germany. This simulation
                      showed that the magnitude of Mg isotope shifts among crops
                      and the exchangeable fraction of Mg in soil is resolvable
                      from the long-term external precision of Mg isotope analyses
                      only if three conditions are met. First, the crop
                      uptake-related Mg isotope fractionation factor should be at
                      the upper end of hitherto published fractionation factors.
                      Second, a high Mg uptake flux of crop plants (e.g., sugar
                      beets) is matched by a low Mg supply from the exchangeable
                      fraction in soil (e.g., sandy soils). Third, subsoil
                      management causes a considerable deepening of the rooting
                      system (e.g., flipping the topsoil root cluster below 30 cm
                      depth). If these conditions are met, Mg stable isotopes can
                      be used in a qualitative manner to identify the main Mg
                      uptake depth, and in a quantitative manner by calculating
                      the Mg use efficiency, defined here as the ratio of Mg
                      uptake versus Mg supply, solely from Mg isotope ratios. This
                      concept was tested for Alfisols on field trials by
                      conducting deep loosening with and without the incorporation
                      of compost. Magnesium isotope shifts in crops and the
                      exchangeable fraction of Mg in soil were mostly unresolvable
                      from the long-term external precision of Mg isotope
                      analyses, which positively tested the Mg isotope concept for
                      well nurtured soils. However, systematic Mg isotope shifts
                      among bulk crops cultivated on and beside a melioration
                      strip were found and attributed to the uplift of
                      isotopically distinct compost-derived Mg on the melioration
                      strip and root restricting layers beside the melioration
                      strip. Given that the Mg isotope composition of the
                      exchangeable fraction barely varies with depth, field-based
                      crop uptake-related ‘apparent’ Mg isotope fractionation
                      factors of winter wheat and spring barley could be
                      determined, which differed from one another
                      (D26Mgwheat-rem.exch. = 0.63 ± 0.05‰,
                      D26Mgbarley-rem.exch. = 0.37 ± 0.12‰). Nonetheless, the
                      quantitative approach of Mg isotopes was violated when
                      calcareous fertilizer was applied to the field as
                      differences in the isotope-derived Mg use efficiency could
                      be attributed to the uneven distribution of lime-derived Mg
                      with depth. Using Mg stable isotopes as a new geochemical
                      routine for agronomy and soil/plant sciences requires future
                      work focussing on isotope fractionation factors related to
                      crop uptake and intra-plant translocation of Mg – which
                      may depend on species, environmental conditions, and
                      nutrient status – to allow minimally invasive sampling of
                      the soil-plant system and to reduce sample sets.},
      cin          = {IBG-3},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {2173 - Agro-biogeosystems: controls, feedbacks and impact
                      (POF4-217)},
      pid          = {G:(DE-HGF)POF4-2173},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000868791500002},
      doi          = {10.1016/j.chemgeo.2022.121114},
      url          = {https://juser.fz-juelich.de/record/909937},
}