Carbon sequestration in soil amended with anaerobic digested matter

Abstract

Organic carbon (C) sequestration in agricultural soils is regarded as a mean to mitigate carbon dioxide (CO2) concentration increase in the atmosphere and to secure food production. Among other practices, exogenous organic matter (EOM) addition in soils is a way to sequestrate organic C. In this study, we compared the organic matter stability, carbon sequestration, soil respiration in soils amended with sucrose, silage EOM and anaerobic digested EOM. We used agricultural soils from a perennial pasture (C3 plants) and EOM from sugar cane and maize (C4 plants). The 13C natural abundance tracer technique has been used to separate SOM-derived and EOM-derived CO2 productions from soil in order to measure EOM stability and priming effects. Undigested-EOM addition did not lead to C sequestration due to a low stability of its organic matter and a positive priming effect that enhanced native SOM respiration. Digested-EOM addition in soil led to C sequestration due to inherent stability of EOM and to a negative priming effect which decreased native SOM respiration. We finally evaluated carbon balance of both direct incorporation of silage in soil and anaerobic digestion followed to incorporation of digestate. Our broad estimation shows that the use of digestate amendment not only favour carbon sequestration but also reduce CO2 emissions by 27% as compared to the incorporation of maize silage.