Historical patterns of forest fertilization in the southeastern United States from 1969 to 2004

Based on historical forest fertilization survey records, over 16 million ac were fertilized in the southeastern United States from 1969 to 2004, with the peak forest fertilizer application in 1999, when 1.59 million ac were fertilized. The 1999 applications were largely on loblolly pine (Pinus toeda L.; 91%) in established stands (78%) and included both nitrogen and phosphorus, typically as urea and diammonium phosphate fertilizers, respectively. On a tonnage basis from 2000 to 2004, the average amount of forest-applied urea and diammonium phosphate represented 2.5% of those materials applied in the United States. The number of acres fertilized approximately doubled every 2 years from 1991 through 1999. This increase can be attributed to a shift in forest production interests to the southeastern United States at a time when research results were showing positive biological and economic responses to nitrogen and phosphorus applications in midrotation southern pine stands. common application rates for nitrogen and phosphorus were 200 and 50 lb elemental nitrogen ac(-1) and 25 and 50 lb elemental phosphorus ac(-1) for stands >2 years old and <= 2 years old, respectively. In 1994, application of elements other than nitrogen and phosphorus, including potassium, boron, and magnesium, began in response to newly available research results. Boron was applied to 30% of the total number of acres fertilized in 2004, likely because boron, when applied with urea, may reduce nitrogen volatilization.