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How do nitrogen inputs to the Changjiang basin impact the Changjiang River nitrate: A temporal analysis for 1968–1997
Author(s) -
Yan Weijin,
Zhang Shen,
Sun Pu,
Seitzinger Sybil P.
Publication year - 2003
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2002gb002029
Subject(s) - nitrate , environmental science , fertilizer , drainage basin , structural basin , hydrology (agriculture) , manure , nitrogen , denitrification , population , nitrogen balance , eutrophication , nutrient , agronomy , ecology , geography , geology , biology , chemistry , paleontology , demography , cartography , geotechnical engineering , organic chemistry , sociology
We present estimates of nitrogen (N) inputs to the Changjiang River basin for the period 1968–1997. The total N input is approximately 7.8 × 10 9 kg in 1997, which is a threefold increase over 1968 levels. N fixation was often a dominant input before 1978, providing about 2.2 × 10 9 kg year −1 , while N fertilizer dominated N input after 1983, supplying an additional input of some 4.4 × 10 9 kg year −1 . More than 40% of total N inputs is converted into manure N, and half of total manure N is returned to agricultural soil. We estimate that the river nitrate concentration and flux have increased about tenfold from 1968 to 1997. Our study suggests that the percent of N inputs to the basin that are exported by the river as NO 3 ‐N has increased steadily over the 30‐year period and that about 30% of total N input is transported through the river. The integrated N input, budget, and storage have been linked to the increasing temporal trends of Changjiang River nitrate. N fertilizer application and human population density, as well as manure N production in the basin, are good predictors of the river's nitrate concentration and flux. Therefore, how N balance is kept (especially for effective application of N fertilizer) is a crucial problem to the sustainable development of the basin.