Repeated fertilisation of crops with manure commonly increases both the amount and the quality of soil organic matter, the mineralisation of which strongly determines the availability of N to plants. In the rhizosphere, the microbial mineralisation/immobilisation of N is enhanced due to rhizodeposition (release of organic compounds from roots). In this work, we studied N transformations during incubation of maize root mucilage in soils that had been previously fertilized with composted pig manure or with ammonium nitrate for 7 years. Our work revealed mucilage was rapidly mineralised (average half-life of 3 days), inducing a rapid N immobilisation of 94 mg N g(-1) of mucilage C, followed by a slow remineralisation. Fertilisation with manure induced a persistent stimulation of the soil organic matter mineralisation, leading to an enhanced content of soil inorganic N (+23% in 58 days of incubation). Due to this stimulation of microbial activity in the soil fertilized with manure, the decrease in inorganic N during the biodegradation of mucilage lasted a shorter time as compared to the mineral fertilisation. However, the type of fertilisation did not significantly change the amount of N immobilised.