Poster (Other)

FZJ-2026-00086

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Assessing Nutrient Dynamics in Hydrochar-Amended Soil with Radiogenic ⁸⁷Sr/⁸⁶Sr Isotope Ratios

Berns, A. E. (Corresponding author)FZJ* ; Moreno Racero, F. J. ; Knicker, H.

2025

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Please use a persistent id in citations: doi:10.34734/FZJ-2026-00086

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

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Contributing Institute(s):

1. Agrosphäre (IBG-3)

Research Program(s):

1. 2173 - Agro-biogeosystems: controls, feedbacks and impact (POF4-217) (POF4-217)

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Database coverage:

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