EGU25-10162, updated on 15 Mar 2025
https://doi.org/10.5194/egusphere-egu25-10162
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Impact of Biochar Aging on Soil Physicochemical Properties
Arthur Gross1, Tamara Apostolovic2, Álvaro Fernando García Rodríguez3, José María de la Rosa4, Bruno Glaser1, Heike Knicker3, and Snežana Maletic2
Arthur Gross et al.
  • 1Martin Luther University Halle-Wittenberg, Institute of Agricultural and Nutritional Sciences, Soil Biogeochemistry, Germany (arthur.gross@landw.uni-halle.de)
  • 2Department of Chemistry, Biochemistry and Environmental Protection, Faculty of Sciences, University of Novi Sad
  • 3Instituto de la Grasa, Consejo Superior de Investigaciones Científicas (IG-CSIC),
  • 4Instituto de Recursos Naturales y Agrobiología de Sevilla, Consejo Superior de Investigaciones Científicas (IRNAS-CSIC),

Biochar undergoes significant transformations in soil as a result of chemical, physical, and biological processes. These alterations can impact its initial properties, influencing both its agronomic effectiveness and its capacity for carbon sequestration. Long-term observations of biochar aging effects in soil are limited but highly relevant, as they provide a more realistic picture of the agronomic and societal benefits of biochar than short-term studies with relatively “fresh” biochar. This study aimed to describe the aging effects of biochar and their impact on a range of soil properties at a long-term biochar experiment in Bayreuth, Germany. For this purpose, soil and biochar samples were taken 13 years after application (two variants: 1. co-composted and 2. pristine biochar) and compared with a fresh variant in which the same unaged biochar was freshly mixed with the control soil.
The soil quality parameters, pH and electrical conductivity, decreased significantly (p < 0.05) during biochar aging. Specifically, the pH dropped from 7.4 in freshly biochar-amended soil to 6.8 in the pristine aged biochar variant and 6.9 in the co-composted aged biochar variant. Electrical conductivity decreased from 217.0 µS cm⁻¹ in the freshly amended soil to 81.1 µS cm⁻¹ in the pristine aged variant and 87.6 µS cm⁻¹ in the co-composted aged variant. Nitrogen retention was enhanced in the soil amended with co-composted aged biochar compared to the pristine aged biochar soil. Total nitrogen (TN) was higher at 1.94 g kg⁻¹ versus 1.57 g kg⁻¹ (p < 0.05), and ammonium-N (NH₄⁺-N) was slightly elevated at 35.7 mg kg⁻¹ versus 33.0 mg kg⁻¹, although the difference was not statistically significant. The nitrate-N (NO₃⁻-N) content was significantly lower in all biochar-amended soil variants compared to the control soil. Total carbon (TC) levels decreased during biochar aging in all soil variants. However, the reduction was significantly lower in the co-composted aged biochar soil (25.0 g kg⁻¹) compared to the pristine aged biochar soil 20.5 g kg⁻¹, p < 0.05).
This study identified multiple aging effects on biochar following 13 years of exposure in loamy soil. Importantly, the results showed that compared to the amendment of pristine biochar, co-composting did not diminish TC of the treated soil, and more N could be retained, 13 years after amendment. In fact, co-composting prior to soil application is recommended to fully realize the potential agronomic benefits. 

How to cite: Gross, A., Apostolovic, T., García Rodríguez, Á. F., de la Rosa, J. M., Glaser, B., Knicker, H., and Maletic, S.: Impact of Biochar Aging on Soil Physicochemical Properties, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10162, https://doi.org/10.5194/egusphere-egu25-10162, 2025.