Description of the Business As Usual (BAU)
In conventional agricultural systems, soil fertility relies mainly on synthetic fertilisers, which provide nutrients but contribute little to carbon recycling. Long-term dependence on mineral fertilisers can reduce or limit the recovery of soil organic carbon compared with systems receiving organic amendments. Limited organic matter inputs often result in declining SOC, weaker soil structure, lower biodiversity, and reduced water-holding capacity. BAU systems may also increase nutrient losses through nitrate leaching and ammonia volatilisation, especially when raw manure is poorly managed. In contrast to organically amended soils, conventionally fertilised soils generally show lower microbial diversity, lower biological soil quality, and greater vulnerability to drought and erosion.
Description of the system change
Organic amendments (OAs) are decomposed or stabilised organic materials added to soils to increase soil organic matter (SOM), supply nutrients, and improve biological soil functions. Common examples include composts, stabilised livestock manures, composted digestates, and processed biosolids.
When incorporated into the soil, OAs provide long-term organic carbon inputs and slow-release nutrients, improving soil fertility, aggregate stability, microbial biomass, nutrient retention, and water-holding capacity. Repeated applications have been shown to significantly increase soil organic carbon (SOC) stocks and enhance resilience to drought and nutrient losses. In perennial crops such as orchards and vineyards, they also improve root- zone structure and support beneficial microbial communities.
Proper stabilisation is essential, as raw manures or digestates may increase N2O or CH4 emissions under unsuitable conditions, while composted materials generally reduce these risks.
Overall, integrating OAs promotes healthier soils with greater biological activity, carbon accumulation, and more efficient nutrient cycling.