Nitrification represents a key N-cycling process because it impacts biome productivity and interferes with the adaptation strategies of plants. Hence, a lot of research has attempted to disentangle the drivers of ammonia oxidation, the rate limiting step of the process. Amongst them a relatively new identified factor that may affect nitrification appears to be arbuscular mycorrhizal (AM) status of plants. Previous work of the applicant has highlighted that a negative relationship operates for the plants that occur in Mediterranean grasslands. The question then is whether this is a specific adaptation of Mediterranean plants or a general consequence of occurrence of AM fungi.In the proposed project the applicant adopts a gradual approach with the following objectives (i) confirm ubiquity of the interaction (ii) achieve a mechanistic understanding of the underlying processes (iii) demonstrate the ecological importance of the interaction when considering nitrification potential rates. The proposed project comprises experiments with a gradual element of difficulty to ensure that some sort of output will be there in the end. Other than ecological and physiological applications the results may be useful in agriculture where a key issue remains to minimize nitrate leaching and N-losses from crops; results of the project may serve as an additional argument for application of AM fungi in agriculture.