This paper reports results from investigations of carbon turnover and the dynamics of carbon and nitrogen in an area with high intensity farming in the black earth region of Central Germany. The long term experiments situated in Bad Lauchstädt provide valuable information about interaction of carbon storage and the efficiency of nitrogen use by the growing crops. Starting from the hypothesis that a sustainable agriculture is bound to make maximum use of diffuse nitrogen inputs from atmosphere, which is estimated to be about 60kg N/ha/a in Bad Lauchstädt, the potentials to control the utilisation of this nitrogen flux will be discussed. A possible benchmark for an environmental sound agricultural system is a N surplus at least lower as N input from atmosphere or better lower than 40kg/ha in order to meet the requierements of water protection. The possibilities for agricultural systems to add nitrogen with organic matter or with mineral fertiliser will be discussed.