ABSTRACT
The use of nitrogen (N) is one of the most important single factors in increasing crop productivity in the last half century. The past 60 years have brought marked advances in the capacity to manufacture and apply plant-available N as commercial fertilizers. These advances, however, have not diminished the importance of problems related to N management but have created a greater appreciation of the importance of avoiding yield-limiting N deciencies (Blackmer, 2000). Close correlations are commonly found between historical crop yields and annual N application rates (Sinclair and Horie, 1989). Similarly, Fageria and Baligar (2005) reported that N is the most limiting nutrient for crop production in many of the world’s agricultural areas and its efcient use is important for the economic sustainability of cropping systems. Adopting appropriate nitrogen management practices is essential to improve N use efciency in crop plants. Further, it also promotes the sustainability of cropping systems. In addition, the dynamic nature of N and its propensity for loss from soil-plant systems creates a unique and challenging environment for its efcient management. Adequate N management practices to improve its efciency involve soil management factors, nitrogen fertilizer management factors, crop management factors, and plant management factors. Hence, the nitrogen economy of crop production involves considerable complexity due to the involvement of several factors and their interactions. Some of these practices are already mentioned in other chapters, and hence there is duplication. However, some duplication is unavoidable due to the importance of some practices in some of the other chapters.
