One of the main approaches for safeguarding food security, sustainable development has increased demand for knowledge on fertilizer management in crop production. Among essential plant nutrients, nitrogen is one of the most important yield-limiting nutrients, mainly responsible for determining yield and yield components in cereals and legumes. It is also responsible for the activation of many enzymes and, of course, plays an important role in photosynthesis. With a recovery efficiency of less than 50 percent in most cropping systems, a large portion of the nitrogen applied as fertilizer is not used by plants, creating environmental and economic issues. covers the critical aspects for the judicious use of nitrogen in cropping systems. This includes appropriate methods of nitrogen application, effective source and timing of application during crop growth cycles, use of an adequate application rate to avoid loss and reduce cost, use of nitrogen-efficient crop genotypes, and use of legumes that fix sufficient amounts of atmospheric nitrogen. There is also a chapter on organic matter and its role in sustainability. This book presents recent information from the international literature, making it relevant for most agroecological regions. Chapters provide experimental results to aid in practical application of the information. The book contains color photos of nitrogen deficiency symptoms to serve as a guide for important crop species, such as rice, dry bean, wheat, soybean, and corn. It also includes numerous tables and figures, providing an easy-to-read reference.