ABSTRACT
Several trends converged a century later to launch the steep climb in world fertilizer use. By mid-century, the frontiers had largely disappeared. The trend in world fertilizer use since mid-century divides into three distinct eras: From 1950 to 1984, annual use climbed from 14 million tons to 126 million tons, expanding ninefold or nearly 7 percent a year—one of the more predictable global economic trends. The new trend in fertilizer use has two components. One is agronomic: the declining response of grain yields to additional fertilizer at higher levels of use. The second is economic, specifically the decision by governments in major food-producing countries to reduce or eliminate fertilizer subsidies. Fertilizers have three key nutrients: nitrogen, phosphorus, and potassium. In India, fertilizer use climbed rapidly in the late eighties, largely as a result of heavy government subsidies.
