EFFECTS OF NITROGEN-FERTILIZATION ON STREAM CHEMISTRY OF JAPANESE FORESTED WATERSHEDS

Citation
K. Ohrui et Mj. Mitchell, EFFECTS OF NITROGEN-FERTILIZATION ON STREAM CHEMISTRY OF JAPANESE FORESTED WATERSHEDS, Water, air and soil pollution, 107(1-4), 1998, pp. 219-235
Citations number
42
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Environmental Sciences","Water Resources","Metereology & Atmospheric Sciences
Journal title
ISSN journal
0049-6979
Volume
107
Issue
1-4
Year of publication
1998
Pages
219 - 235
Database
ISI
SICI code
0049-6979(1998)107:1-4<219:EONOSC>2.0.ZU;2-X
Abstract
Steam chemistry was investigated from May 1991 through April 1992 for 13 Japanese forested watersheds and from May 1990 through August 1994 for two of these watersheds. Nine watersheds were treated over differe nt periods (1983-1991) with different amounts of N (nitrogen) fertiliz er as urea and ammonium salts. Total N additions ranged from 20 to 375 kg ha(-1). There were no distinct seasonal differences in stream NO3- concentrations in either the treated or untreated watersheds, but con centrations tended to be somewhat higher during periods of high discha rge. The annual average NO3- concentrations in streams had a significa nt, positive (p < 0.001, r = 0.84) relationship to the total amount of N applied from 1985-1991. The application of 330 kg N ha(-1) raised a nnual average stream NO3- concentration to about 300 mu eq L-1 compare d to less than 160 mu eq L-1 in untreated watersheds. The concentratio ns of K+, Ca2+, and Mg2+ in stream water also increased in those water sheds with high rates of N fertilizer as a result of nitrification tha t increased the generation of the mobile nitrate anion. The lack of se asonality in stream NO3- concentrations and the large rates of N loss with N addition both suggest that these watersheds were 'nitrogen satu rated'.