Current and potential recycling of exogenous organic matter as fertilizers and amendments in a French peri-urban territory

摘要

Animal breeding, industries and cities produce byproducts and wastes that can be recycled in agriculture as exogenous organic matters (EOMs), promoting soil carbon storage and nutrient recycling. Peri-urban areas show a strong potential for recycling urban EOMs in agriculture. This potential needs to be better quantified in regard to farmer fertilizer demand. We investigated this question in a peri-urban territory, namely, the Versailles plain, which is located near Paris, France. We coupled interviews with farmers and waste managers with regional datasets to identify accurate flows of organic matter and their associated nutrients. The EOM potential for C storage was assessed with the AMG soil carbon model. Potentials for P, K and (short-term) N fertilizer substitutions were based on fertilizer equivalent coefficients. Additionally, we assessed the potential additional mineral N release related to increased soil organic matter after repeated EOM applications. For social and technical reasons, local EOM recycling was unequal; it was high for manures and compost and low for sewage sludge. Inputs of efficient C into soils due to EOM recycling corresponded to 20% of the inputs from crop residues. Current EOM use met 44% and 50% of the crop P and K demands, respectively. The potential for N fertilizer substitution was very low but increased when considering the additional mineral N available after long-term EOM applications. EOM could reach higher potential, especially when considering the anaerobic digestion of biowaste and potential source-separation of human urine (up to the whole P and K demand and half of N demand).