One third of the agricultural land worldwide has been degraded. Soil erosion, soil organic carbon (SOC) depletion and nutrient imbalance are the most severe threats to soil. Organic amendments (OAs) are the most known and time-tested materials to replenish organic carbon in soils and improve fertility. Pre-treatment technologies (such as composting, anaerobic digestion, and fermentation) can be used to produce OAs. This thesis demonstrates that OA chemistry is modulated by these technologies having implications on their effect on soil properties. This knowledge suggests that it is possible to design and produced OAs that can replenish SOC and nutrient content more efficiently while improving other soil characteristics (soil aggregate formation, microbial activity and diversity, microbial biomass, and biofilm formation). Even further, it is possible to reduce the green house gas (GHG) emission derived from the addition of OAs in soil.