The results of years" research (n=600) in diagnostics and optimization of the conditions of crops" nitrogen nutrition are considered in this article. The methodological approach to the evalua tion of soil nitrogen state and crops with nitrogen is exp licated. New method of determining the needs and dose calculation in nitrogen fertilizers with individual requirements of crop and the main factors defining their effectiveness is represented. A model predict ing the effectiveness of fertilizers is also presented. The developed technique allows purposefully manage soil nitrogen regime supplying optimization of nutrition and implementation of crops" potential possibilit ies.