"Urea as fertilizer." . . "Nitrogen fertilizers." . . "Douglas fir." . . . . "Pacific Northwest Forest and Range Experiment Station (Portland, Or.)" . . . . . . . . . . . . . . . . . . . . . . . . . . "Response to urea and ammonium nitrate fertilization in an 80-year-old Douglas-fir stand" . . "Response to urea and ammonium nitrate fertilization in an 80-year-old Douglas-fir stand"@en . . . . "United States. Forest Service." . . "Ammonium nitrate." . .