Fertilizer nitrogen is the single ‘Most Variable Production Input’ which farmers used in crop production. Most of the Indian soils are low in N and the requirement of N by crop is throughout its growing period, therefore, N should be applied in such a way that plant gets it throughout its life period. It becomes absolutely necessary to apply N fertilizers to every soil and crops. For this reason, the total requirement of N is more compared to fertilizers of other group. With the continued increase in fertilizer costs, nitrogen use efficiency becoming increasingly important for production as well as environmental quality. Hence, it helps in saving the N fertilizers and ultimately low cost of cultivation and less environmental impact. The major aim to reviewed this article to aware about the nitrogen, its impact over long use in environment, nitrogen use efficiency, smart management practices, new approaches of its application and whatever research to be needed regarding nitrogen would be helped to young researchers.