This data set contains county-level estimates of nitrogen and phosphorus from fertilizer, for both farm and nonfarm uses, for the conterminous United States, for 1987 through 2012. State-level farm and nonfarm nitrogen and phosphorus were derived from the Association of American Plant Food Control Officials (AAPFCO) commercial fertilizer sales data. State estimates were then allocated to the county-level using fertilizer expenditure from the Census of Agriculture as county weights for farm fertilizer, and effective population density as county weights for nonfarm fertilizer. Data computations for 2007 - 2012 estimates are results of methods applied directly from Gronberg and Spahr, 2012. Data for 1987 - 2006 are exactly those published in Gronberg and Spahr, 2012.
Gronberg, J.M., and Spahr, N.E., 2012, County-level estimates of nitrogen and phosphorus from commercial fertilizer for the Conterminous United States, 1987–2006: U.S. Geological Survey Scientific Investigations Report 2012-5207, 20 p. - https://pubs.usgs.gov/sir/2012/5207/
