What goes up must come down and back up again

U.S. prices of fertilizer nutrients began to rise steadily in 2002 and increased sharply to historic highs in 2008 due to the combined effects of a number of domestic and global long- and shortrun supply and demand factors. From 2007 to 2008, spring nitrogen prices increased by a third, phosphate prices nearly doubled, and potash prices doubled. The price spike in 2008 reflects low inventories at the beginning of 2008 combined with the inability of the U.S. fertilizer industry to quickly adjust to surging demand or sharp declines in international supply. Declining fertilizer demand, disruption in fall applications, increased fertilizer imports (July to August), and tightening credit markets for fertilizer purchases contributed to the decline of fertilizer prices in late 2008. The prospect for strong fertilizer demand in early 2009, high raw material costs for the manufacture of fertilizers, production cutbacks, and decreasing supplies from fertilizer imports, however, could put upward pressure on U.S. fertilizer prices in spring 2009.

See http://www.ers.usda.gov/Publications/AR33/