i NITROGEN AND PHOSPHORUS BUDGETS FOR IOWA AND IOWA WATERSHEDS Iowa Geological Survey Technical Information Series 47 R.D. Libra, C.F. Wolter and R.J. Langel Iowa Department of Natural Resources-Geological Survey 109 Trowbridge Hall, Iowa City, IA 52242 Supported, in part, through grants from the U.S. Environmental Protection Agency, Region VII, Nonpoint Source Program December 2004 Iowa Department of Natural Resources Jeffrey R. Vonk, Director