Before the advent of widespread fertilizer use, crops relied solely on compounds in the soil to fuel their growth. The application of commercial fertilizer, however, has been one of the biggest changes to impact farming.
Commercial fertilizer, a blend of nitrogen, phosphate and potash, allows farmers to realize high yields on their crops and to use the same plot of land year upon year for their crops. This makes projecting profits more reliable and eliminates the need to clear new ground for fields [source: Agro Services International].
Farmers began applying commercial fertilizer about the same time as the first self-propelled tractors hit the market in the late 1880s. Between 1890 and 1899, American farmers applied more than 1.8 million tons (1.6 million metric tons) of commercial fertilizer each year. By 1989, the number had grown to more than 47 million tons (43 million metric tons) annually [source: Agriculture in the Classroom]. Globally, 185.1 million tons (168 million metric tons) of fertilizer were used in 2008 [source: The Fertilizer Institute].
All that fertilizer has raised some environmental concerns. Nitrates, a major component of fertilizers (including those applied to lawns and gardens), can contaminate groundwater and pose a health risk to infants and at-risk populations. Therefore, farmers should be careful in how they store, use and dispose of fertilizer [source: Harris].