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@INPROCEEDINGS{Berns:1050274,
      author       = {Berns, Anne E. and Moreno Racero, Francisco J. and Knicker,
                      Heike},
      title        = {{A}ssessing {N}utrient {D}ynamics in {H}ydrochar-{A}mended
                      {S}oil with {R}adiogenic ⁸⁷{S}r/⁸⁶{S}r {I}sotope
                      {R}atios},
      reportid     = {FZJ-2026-00086},
      year         = {2025},
      abstract     = {Hydrochar (HC) amendments can enhance soil health, promote
                      microbial activity, and support plantproductivity. Among
                      their various properties, hydrochars also retain nutrient
                      elements from the originalbiomass feedstock offering plants
                      an alternative nutrient source. Understanding the
                      interactions betweenthese carbonaceous materials and the
                      soil–plant system is essential for optimizing their
                      application andenvironmental impact.In this study, we
                      employed radiogenic strontium isotope ratios
                      (⁸⁷Sr/⁸⁶Sr) as a geochemical proxy forcalcium
                      (Ca)[1-2] to trace nutrient sources in a pot experiment with
                      sunflower cultivation, conducted inthe greenhouse facilities
                      of IG-CSIC in Seville. Sr isotopes are particularly
                      advantageous as they are notfractionated during plant uptake
                      or translocation, making them robust tracers for assessing
                      sourcecontributions within the soil–plant
                      continuum.[3-5]Analyses of Sr-isotope compositions in soil,
                      HC, and sunflower leaves revealed that, despite
                      substantialdifferences in Sr-isotope ratios of the total Sr
                      pools between source materials (0.70618 ± 0.00006 in
                      soilvs. 0.71331 ± 0.00096 in HC), the Sr-isotope ratios of
                      the plant-available Sr pools in HC(0.70849 ± 0.00001) and
                      soil (0.70926 ± 0.00003) were more closely aligned.
                      Correspondingly, the⁸⁷Sr/⁸⁶Sr ratios in plants
                      (range: 0.70935 - 0.70947) were indifferent from those in
                      control treatments,regardless of fertilization or irrigation
                      regime. These findings indicated that plant Sr uptake
                      originatedfrom the native soil pool (see
                      figure).Quantitative analysis of the plant-available Sr
                      pools in soil and HC confirmed the minimal contributionof
                      HC. Only 0.015 $\%$ Sr and 0.03 $\%$ Sr in the HC-3.5 and
                      HC-6.5 treatments, respectively, werecontributed by HC to
                      the overall plant-available Sr-pool in each pot. This low
                      incorporation explainedthe absence of any detectable shift
                      in plant Sr-isotope signatures despite the isotopic contrast
                      betweenHC and soil. Ca contributions from HC were similarly
                      low - 0.055 $\%$ and 0.11 $\%$ Ca in theplant-available Ca
                      pools of HC-3.5 and HC-6.5, respectively.While HC provides
                      various agronomic benefits, the impact of this specific HC
                      as a significant Sr (andby extension Ca) source for
                      short-term plant uptake appears negligible under the tested
                      conditions.Nevertheless, these findings demonstrate the
                      utility of Sr isotopes in disentangling nutrient dynamics
                      inamended soils. However, effective source tracking
                      requires: (i) the isotopic Sr ratios of the relevantpools
                      must differ substantially and (ii) potential contributions
                      to the nutrient pool should exceed $10\%.REFERENCES[1]$ RC
                      Capo, BW Stewart, OA Chadwick, Geoderma 82 (1998)
                      197−225[2] N Bélanger, C Holmden Can J Soil Sci 90 (2010)
                      267–288[3] A Aguzzoni, M Bassi, P Robatscher, F
                      Scandellari, et al. J Agric Food Chem 67 (2019)
                      5728−5735[4] D Uhlig, W Amelung, F von Blanckenburg,
                      Global Biogeochem Cycles 34 (2020) e2019GB006513[5] D Uhlig,
                      AE Berns, B Wu, W Amelung Plant Soil 489 (2023) 613–628},
      month         = {Sep},
      date          = {2025-09-08},
      organization  = {Eurosoil 2025, Sevilla (Spain), 8 Sep
                       2025 - 12 Sep 2025},
      subtyp        = {Other},
      cin          = {IBG-3},
      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)24},
      doi          = {10.34734/FZJ-2026-00086},
      url          = {https://juser.fz-juelich.de/record/1050274},
}