The current alarming rate of decline of earth's natural resources, particularly of the reserves of rock phosphate and fossil fuel, is of great concern for the future of agriculture, particularly in developing countries. Not surprisingly, sustainable crop production remains a major global challenge and has drawn increasing attention among policy makers, business, and the scientific community. The agricultural use of land for crop production leads to the continuous extraction of soil nutrients. In the absence of adequate nutrient replenishment, a subsequent decrease of soil nutrient availability may occur, exerting a negative effect on yield. This book deals with strategies to overcome low nutrient availability in soils mainly rely on the use of fertilizers and crop breeding.