The paper describes a mesocosm (pot) experiment which provides the possibility for multiparametric evaluation of N-flows required for an ecological approach to N-cycIing in a soil/plant/atmosphere system. The quantitative distribution of nitrogen between different pools is presented and particular emphasis is given to the contribution of soil mesofauna. The determination of a wide spectrum of cumulative N-flows (soil-N in NO3−, NH4+and active organic pools, plant uptake, mesofaunal N-content, gaseous N-losses) indicates the change of N- transformation dynamics which may be studied by supplementary testing of microbiological and mesofaunal activity joint to the basic experimental model.