Estimates of nitrogen-fertilizer sales for the conterminous United States in 1989

This coverage contains estimates of nitrogen-fertilizer sales for the conterminous United States in 1989 as reported by the U.S. Environmental Protection Agency (1990) and by Jerald Fletcher (West Virginia University, written commun., 1992). Nitrogen-fertilizer sales estimates in this coverage are reported for each county polygon in tons of actual nutrient sold (inorganic nitrogen, phosphate, and potash) as distinct from total tons of fertilizer product. The data are summarized for fertilizer years (i.e. the 1987 fertilizer year runs from July 1, 1986 to June 30, 1987). The polygons representing county boundaries in the conterminous United States, as well as lakes, estuaries, and other nonland-area features were derived from the Digital Line Graph (DLG) file representing the 1:2,000,000-scale map in the National Atlas of the United States (1970). Nitrogen-fertilizer Commercial fertilizer Fertilizer use Counties United States本数据集包含1989年美国本土（conterminous United States）的氮肥销售额估算值，数据来源为美国环境保护署（U.S. Environmental Protection Agency，1990年报告）以及杰罗德·弗莱彻（西弗吉尼亚大学，1992年书面通信）。本数据集的氮肥销售额估算以县界多边形（county polygon）为统计单元，统计单位为实际销售的纯养分吨数（包括无机氮、磷和钾），该口径与肥料产品总吨数的统计方式存在本质差异。 本数据按照肥料年度（fertilizer year）进行汇总，例如1987肥料年度的时间跨度为1986年7月1日至1987年6月30日。 用于表示美国本土县界、湖泊、河口及其他非陆地区域的多边形要素数据，均源自美国国家地图集（National Atlas of the United States，1970年版）中1:200万比例尺地图对应的数字线划图（Digital Line Graph，DLG）文件。 氮肥（Nitrogen-fertilizer） 商品肥料（Commercial fertilizer） 肥料施用（Fertilizer use） 县（Counties） 美国（United States）