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Nitrogen Losses in Surface Runoff from Agricultural Watersheds on Missouri Valley Loess
Author(s) -
Schuman G. E.,
Burwell R. E.,
Piest R. F.,
Spomer R. G.
Publication year - 1973
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/jeq1973.00472425000200020030x
Subject(s) - surface runoff , watershed , environmental science , hydrology (agriculture) , leaching (pedology) , sediment , loess , pasture , agronomy , soil water , soil science , geology , ecology , biology , paleontology , geotechnical engineering , geomorphology , machine learning , computer science
Nitrogen losses from surface runoff from four field‐size (30 to 60.8 ha) watersheds in southwestern Iowa, near Treynor, were measured during 1969, 1970, and 1971. A contour‐planted corn watershed and a pasture watershed were fertilized at the recommended N rate (168 kg/ha). A level‐terraced and a contour‐planted corn watershed were fertilized at 2.5 times this rate. The conservation practice of level‐terraced corn or pasture was very effective in reducing water, sediment, and N yields when compared with the contour‐planted corn watersheds. Annual water‐soluble N losses were low from all watersheds. The 3‐year average annual solution N loss from the contour‐planted corn watershed, fertilized at 2.5 times the recommended rate, was 3.05 kg/ha; the comparable watershed, fertilized at the recommended rate, lost only 1.89 kg/ha. Nitrogen losses associated with sediment in the runoff accounted for 92% of the total loss for the 3‐year period from the contour planted corn watersheds. A large portion of the N loss for the terraced watershed was also associated with the sediment; however, N loss was only one‐tenth that of the contour‐planted watersheds. Sediment‐N concentrations were similar for watersheds receiving 168 kg/ha and 448 kg/ha annual N applications. Water‐soluble‐N and sediment‐N losses in runoff were usually highest at the beginning of the cropping season and decreased progressively throughout the year, reflecting a seasonal effect believed to be associated with nutrient removal by the crop, leaching, and N tie‐up in organic matter.