Abstract. Our experiment evaluated the effect of maize and peanut mulched residues upon soil organic matter and denitrifying community over a five-week incubation in soil microcosms. Soil organic matter under peanut and maize debris contrasted in biochemical quality throughout incubation, despite identical soil C contents that were significantly increased by both organic amendments. Moreover, only soluble extracts originating from the peanut treated soils could significantly fuel semi-potential denitrification. Accordingly, the composition of the nirK and nosZ communities was also specifically affected by mulch type, and the strongest impact was registered within the nosZ gene-bearing denitrifiers under peanut residues. Residue enriched soils displayed temporal patterns of potential denitrification activity that were also dependant on residue type. The highest overall emission rates were recorded with soils under maize mulch but they were not mirrored by direct N2O contents of the microcosm’s headspace. Overall, both soil organic matter and denitrifiers community changes were conditioned throughout the decomposition kinetics by the original quality of mulched crop residues. However, the denitrification activity was decoupled both from the composition of the denitrifying community and from the soil organic matter quality.
Keywords: soil denitrification, mulched crop residues, dissolved organic matter, nitrous oxide.