chapter 1. Functions of nitrogen in crop plants -- chapter 2. Nitrogen losses in soil-plant system -- chapter 3. Diagnostic techniques for nitrogen requirements in crop plants -- chapter 4. Management of soil organic matter -- chapter 5. Nitrogen use efficiency in crop plants -- chapter 6. Nitrogen interaction with other nutrients -- chapter 7. Biological nitrogen fixation by legumes -- chapter 8. Management practices to improve nitrogen use efficiency in crop plants.