Table 1.

Four categories of practices (see also the reviews by Dignac et al. 2017; Chenu et al. 2019; Amelung et al. 2020) with expected positive effects on C storage in soil are distinguished according to the mechanisms targeted: C input (practices that increase the input of C to soil); N input (practices that increase the input of N to soil); biology (practices that aim to maintain microbiological and biological life in soil); inaccessibility (practices that impede decomposers access to organic matter). Expected positive effects and potential negative effects of these practices.

Mechanism	Management measures	Expected positive effects	Potential negative impacts
C input	Forestry: nonexporting harvest residues Grassland: choosing grazing over mowing Cropping: increasing soil OM input by: • Returning crop residues • Adding exogenous OM, incl. after transformation: e.g., organic waste products (Lashermes et al. 2009), biochars (Naisse et al. 2013; Hagemann et al. 2017) • Selection of plants with highly developed root systems or hyperexudative roots (Rasse et al. 2005) Associations for increasing C input diversity and quantity: • Rotations with permanent soil cover • Ley grassland • Agroforestry (Cardinael et al. 2017) • Silvo-pastoralism (Francaviglia et al. 2012)	Increase in C stock Addition of C mainly in the form of POM, no saturation issue POM input feeding of MAOM Improvement of soil physical and chemical fertility Improvement of soil life, better element cycling (Drinkwater and Snapp 2007) Transformed OM more persistent in soil (Möller 2015; Paolini et al. 2018)	Acceleration of OM turnover due to microbial growth and priming (Bernard et al. 2022; Perveen et al. 2019) POM sensitive to climate crisis events such as fire, warming Additional nutrient needs due to SOM stoichiometry constraints (Richardson et al. 2014) Addition of contaminants present in organic inputs Over-fertilization due to imbalance between the nutrient content of additional input and plant needs NH3, N2O emissions (Janz et al. 2021; Lashermes et al. 2021)
N input	Mineral N fertilization Introduction of N-fixing crops of the legume family N fertilization by human urine	Increased plant input to the soil due to increased primary production, Decrease in N-rich organic matter mining Supported production of N-rich microbial compounds, expected to persist in soil	Decreased C allocation to root inducing a decrease in soil C storage (Janssens et al. 2010) Nitrate and ammonia leaching and N2O emissions (Lemaire et al. 2021) Issue of social acceptance of urine fertilization (Martin et al. 2020)
Biology	Agro-ecological practices, such as non-tillage or no pesticide, implemented in the long-term favoring soil biotic legacy (Fanin and Bertrand 2016; Lu et al. 2018; Sauvadet et al. 2018),	Formation of biogenic structures enhancing SOM persistence (Lubbers et al. 2017) Better element cycling (Drinkwater and Snapp 2007) Enhancement of microbial compounds production, expected to persist in soil (Kallenbach et al. 2019)	Increased contribution of decomposer activity to CO2 production (Lubbers et al. 2013; Lejoly et al. 2021)
Spatial accessibility	Selection of plant species with deep root development favoring C input in the deep soil horizons, where biological activity is low (Rumpel and Kögel-Knabner 2011)	Increased C residence times compared to topsoil input (Balesdent et al. 2018)	Decrease in C storage due to stimulation of deep decomposer activity through fresh material supply (priming effect – Henneron et al. 2022)
	Liming	pH rise that facilitates OM/mineral interactions
	Addition of mining or quarry wastes	Promotion of organomineral association formation
	Reduced tillage or no-tillage (high controversy) (Dimassi et al. 2014)	Restriction of OM access to decomposers Enhanced substrate-decomposer contact at the macroscopic scale (mulch incorporation, grinding to reduce substrate size) (Angers et al. 1997) or at the microscopic scale (aggregate reorganization) (Six et al. 2000) Erosion control (Sun et al. 2015)	Accumulation of large amounts of plant residues at the soil surface where decomposer activity is most intense, instead of redistributing it over the soil profile Increase in N2O emissions (Guenet et al. 2021)