Changes in microbial utilization and fate of soil carbon following the addition of different fractions of anaerobic digestate to soils

Applying digestate, the residue from anaerobic digestion, to soil as a replacement for inorganic fertiliser is of growing interest in agriculture. However, impacts different fractions digestate on carbon (C) cycle remain unclear and provide focus research reported here. We examined effects applying whole (WD) solid (SD) dioxide (CO2C) efflux, concentrations dissolved organic (DOC), microbial biomass C (Cmicro) phospholipid fatty acids, alongside use efficiency (CUE). A 21-day laboratory microcosm incubation was used investigate when applied two grassland soils high versus low initial nutrient content. Application rates SD WD were based recommended nitrogen (N) inputs these materials. Compared control treatments, cumulative CO2C efflux concentration DOC increased significantly after application, although only within soil. Both Cmicro fungal-to-bacterial ratio following regardless These observations are likely reflect larger input C, dominance more strongly lignified compounds, associated with compared achieve constant N application rate. Our results also indicate that generated CUE. The led increases positive values CUE, whereas decreases negative CUE observed application. findings emphasize need carefully plan management agricultural production systems, minimize storage whilst maximizing agronomic value derived digestate. Highlights Past has not fully elucidated cycle. Soil status + fraction shown impact community efflux. Solid efficiency.