Improving organic fertilization practices: A long-term field experiment assessing the effects of combining anaerobic digestate with other organic waste products
The PROspective field experiment was conducted in northeastern France and was set up in 2000. Its primary objective is to systematically evaluate the agronomic value and environmental impact of OWPs in the context of land application policies. The present study aimed to assess the effect of anaerobic digestate combined with different OWPs (digestate acts as an additional N-supply source) on soil microbial communities (Archaea, Bacteria, and Fungi), using molecular DNA-based tools to quantify soil microbial biomass, diversity, and community structure. To our knowledge, no prior study has employed an in-situ approach to assess the impact of different OWPs coupled with anaerobic digestate on soil microbial parameters. We hypothesized that (i) soil physicochemical properties and soil microbial parameters (such as molecular microbial biomass, diversity, community structure, and composition) are subject to changes due to the repeated application of anaerobic digestate as an organic fertilizer, and these modifications differ when a traditional inorganic mineral fertilizer is used instead, and (ii) the cumulative long-term effects of repeated applications of distinct OWPs, combined with two different additional sources of N-supply—via an organic source (digestate) or a chemical source (mineral fertilizer)—vary significantly, but these differences depend on the type of OWP applied.