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https://doi.org/10.5194/egusphere-2024-107
https://doi.org/10.5194/egusphere-2024-107
30 Jan 2024
 | 30 Jan 2024

Soil organic carbon mineralization is controlled by the application dose of exogenous organic matter

Orly Mendoza, Stefaan De Neve, Heleen Deroo, Haichao Li, Astrid Françoys, and Steven Sleutel

Abstract. Substantial input of exogenous organic matter (EOM) may be required to offset the projected decline in soil organic carbon (SOC) stocks in croplands caused by global warming. However, information on the effectivity of EOM application dose in preserving SOC stocks is surprisingly limited. Therefore, we set up a 90-day incubation experiment with large soil volumes (sandy loam and silt loam) to compare the mineralization of EOM (13C-labelled ryegrass) and SOC as a function of three EOM application doses (0.5, 1.5, and 5 g dry matter kg-1 soil). In the sandy loam soil, the percentage of mineralized EOM was not affected by EOM dose, while SOC mineralization increased proportionally with increasing EOM dose (+49.6 mg C per g EOM). In the silt loam soil, the percentage of mineralized EOM decreased somewhat with increasing dose, while SOC mineralization increased at a higher rate than in the sandy loam soil (+117.2 mg C per g EOM). In both textured soils, increasing EOM dose possibly supplied energy for microbial growth and enzyme production, which in turn stimulated mineralization of native SOC (i.e. co-metabolism). Higher soil macroporosity at higher EOM doses in the silt loam soil could have contributed to sustaining aerobic conditions (indicated by soil Eh) and promoting SOC priming as shown by positive relationships between pore neck size classes 43–60, 60–100 and >300 μm and SOC priming, suggesting a new mechanism for understanding SOC priming. In sum, this experiment and our previous research suggest that EOM mineralization is mostly independent of EOM dose, but EOM dose modulates mineralization of native SOC. These findings tentatively indicate that using larger EOM doses could help preserve more of added EOM-C in silt loam soils, but longer-term confirmation in the field will firstly be required before we could draw any conclusion for soil C management.

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Orly Mendoza, Stefaan De Neve, Heleen Deroo, Haichao Li, Astrid Françoys, and Steven Sleutel

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-107', Anonymous Referee #1, 13 Feb 2024
    • AC1: 'Reply on RC1', Orly Mendoza, 09 Jun 2024
  • RC2: 'Comment on egusphere-2024-107', Julia Schroeder, 28 Feb 2024
    • AC2: 'Reply on RC2', Orly Mendoza, 09 Jun 2024
Orly Mendoza, Stefaan De Neve, Heleen Deroo, Haichao Li, Astrid Françoys, and Steven Sleutel
Orly Mendoza, Stefaan De Neve, Heleen Deroo, Haichao Li, Astrid Françoys, and Steven Sleutel

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Short summary
Farmers frequently apply fresh organic matter such as crop residues to soil to boost its carbon content. Yet, one burning question remains: Does the quantity of applied organic matter affect its decomposition and that of native soil organic matter? Our experiments indicate that smaller application doses might deplete soil organic matter more rapidly. In contrast, applying intermediate or high doses might be a promising strategy for maintaining it.