Fertilizers have been largely responsible for the massive increases in world food production in the past half century that permitted accelerated global population growth to current unprecedented levels. Fertilizer use not only impacts crop yields but also affects animal production. While nitrogen (N) has been the main driver of such changes, phosphorus (P) also has a major role. Like N, the use of P fertilizers can have implications beyond the farmers' fields, if excessive amounts are applied. The past four decades have witnessed overuse of P fertilizers as well as animal manures in the intensive agricultures of some European countries and North America. Yet ironically in many areas of the world, notably Africa, agricultural output is largely constrained by low soil P in combination with little or no P fertilizer application. Rock phosphate is the global source of the raw material for P fertilizer. However, resources are finite, and therefore efficient and wise use is of paramount importance.