Denitrification from a swine lagoon overland flow treatment system at a pasture-riparian zone interface.
In manure disposal systems, denitrification is a major pathway for N loss and to reduce N transport to surface and ground water. We measured denitrification and the changes in soil N pools in a liquid manure disposal system at the interface of a pasture and a riparian forest. Liquid swine manure was applied weekly at two rates (approximately 800 and 1600 kg N ha-1 yr-1) to triplicate plots of overland flow treatment systems with three different vegetation treatments. Denitrification (acetylene block technique on intact cores) and soil N pools were determined bimonthly for 3 yr. The higher rate of manure application had higher denitrification rates and higher soil nitrate. Depth 1 soil (0-6 cm) had higher denitrification, nitrate, and ammonium than depth 2 soil (6-12 cm). The vegetation treatment consisting of 20 m of grass and 10 m of forest had lower denitrification. Denitrification did not vary significantly with position in the plot (7, 14, 21, and 28 m downslope), but nitrate decreased in the downslope direction while ammonium increased downslope. Denitrification ranged from 4 to 12% of total N applied in the manure. Denitrification rates were similar to those from a nearby dairy manure irrigation site, but were generally a lower percent of N applied, especially at the high swine effluent rate. Denitrification rates for these soils range from 40 to 200 kg N ha-1 yr-1 for the top 12 cm of soil treated with typical liquid manure that is high in ammonium and low in nitrate.
Lowrance
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Southeast Watershed Research Lab., USDA-ARS, P.O. Box 946, Tifton, GA 31793, USA. lorenz@tifton.cpes.peachnet.edu
Hubbard
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D000383:Agriculture; D000818:Animals; D008372:Manure; D009566:Nitrates; D009584:Nitrogen / Q000378:metabolism*; D010944:Plants; D000644:Quaternary Ammonium Compounds; D012037:Refuse Disposal; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism*; D013552:Swine; D014876:Water Pollution
D008372:Manure; D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D012989:Soil Pollutants; D009584:Nitrogen