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Agriculture and Water Quality in the Canadian Great Lakes Basin: IV. Nitrogen
Author(s) -
Neilsen G. H.,
Culley J. L. B.,
Cameron D. R.
Publication year - 1982
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1982.00472425001100030034x
Subject(s) - hydrology (agriculture) , surface runoff , watershed , environmental science , manure , water quality , soil water , fertilizer , surface water , nonpoint source pollution , kjeldahl method , pollution , agronomy , nitrogen , environmental engineering , soil science , ecology , chemistry , geotechnical engineering , organic chemistry , biology , machine learning , computer science , engineering
Eleven agricultural watersheds in southern Ontario were sampled approximately 3,000 times during the years 1975–1977 for Total Kjeldahl N (TKN) and NO 3 ‐N as part of the Canadian activities of the Pollution from Land Use Activities Reference Group (PLUARG). Only 12% of runoff samples had NO 3 ‐N concentrations below 0.3 mg L −1 , while 3% of the samples exceeded the 10‐mg L −1 Ontario drinking water standard. Two‐year‐average total N stream loadings ranged from 3.5 to 29.2 kg N watershed‐ha −1 . The NO 3 ‐N loads averaged 75% of total N loads over all 11 watersheds. Both NO 3 ‐N and total N unit‐area loads were significantly correlated with total N addition to the watershed, and with percent of watershed under cultivation, in row‐crops and corn ( Zea mays L.), or tile‐drained. The TKN loads were positively correlated with watershed surface‐soil clay content and with extent of soils with high surface runoff potential. Remedial measures to reduce stream N loading should only be considered for watersheds where stream N loading much exceeds inputs of N from precipitation. In these watersheds, improved fertilizer N efficiency in corn production may provide the greatest potential for reduced stream N loading. Proper location of manure storage sites is most important to minimize N pollution from livestock activities. About 70% of both stream NO 3 ‐N and total N loading occurred from January to April during the spring runoff season. Agronomic practices that reduce either postharvest teachable soil N or erosion during spring runoff merit future research.