EGU21-16469
https://doi.org/10.5194/egusphere-egu21-16469
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Effects of organic soil amendments on soil greenhouse gas exchange under controlled soil moisture conditions

Kenneth Peltokangas1,2, Jussi Heinonsalo2,4,5, Kristiina Karhu3,6, Liisa Kulmala2,5, Jari Liski2, and Mari Pihlatie1,5,7
Kenneth Peltokangas et al.
  • 1Department of Agricultural Sciences, University of Helsinki, Faculty of Agriculture and Forestry, Finland
  • 2Finnish Meteorological Institute, Helsinki, Finland
  • 3Department of Forest sciences, University of Helsinki, Faculty of Agriculture and Forestry, Finland
  • 4Department of Microbiology, University of Helsinki, Faculty of Agriculture and Forestry, Finland
  • 5Institute for Atmospheric and Earth System Research (INAR), Helsinki, Finland
  • 6Helsinki Institute of Life Science (HiLIFE), University of Helsinki, Finland
  • 7Viikki Plant Science Centre (ViPS), University of Helsinki, Faculty of Agriculture and Forestry

Organic soil amendments are proposed to mitigate climate change and support soil fertility by introducing recalcitrant carbon into soil. However, the full impact of recycled biosolids on soil greenhouse gas (GHG) dynamics are still unknown. We conducted a laboratory incubation to assess the climatic effects of two biochars (willow and spruce) and two ligneous biosolids on GHG emissions in controlled moisture conditions. The soil used in the incubation was collected from a soil-amendment field experiment on a clay cropland in South-West of Finland. The soil was sieved, air-dried and then individual samples were adjusted to 25%, 50%, 80% and 120% of water filled pore space (WFPS) before being incubated for 32 days in laboratory conditions. Soil GHG fluxes were measured after 1, 5, 12, 20 and 33 days.  

The application of 20–40 Mg ha-1 of ligneous amendments, two years prior to our experiment, had increased soil pH, soil organic carbon content and plant available water content. The carbon dioxide (CO2) fluxes were unaffected by the amendment treatments and correlated mainly with soil moisture and microbial biomass. Nitrous oxide (N2O) emissions were reduced by all amendments compared to the un-amended control. Methane (CH4) exchange consisted mostly of slight uptake by the soil but played only a minor role in the total GHG budget overall. 

The sum of CO2, N2O and CH4 emissions, calculated as CO2-equivalents, exhibited a strong linear relationship with soil moisture. Where the GHG budget was dominated by CO2, it was accompanied by significant N2O emissions at 120% WFPS. The results indicate that soil moisture critically affects the GHG emissions and that while organic soil amendments may have persisting effects on GHG exchange, they primarily occur in water-saturated conditions through N2O dynamics.

How to cite: Peltokangas, K., Heinonsalo, J., Karhu, K., Kulmala, L., Liski, J., and Pihlatie, M.: Effects of organic soil amendments on soil greenhouse gas exchange under controlled soil moisture conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16469, https://doi.org/10.5194/egusphere-egu21-16469, 2021.

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