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Ionic Composition and Nitrate in Drainage Water From Fields Fertilized with Different Nitrogen Sources, Middle Swamp Watershed, North Carolina, August 2000–August 2001

Scientific Investigations Report 2004–5123
By Stephen L. Harden and Timothy B. Spruill


Complete report in PDF (20 pages, 3.3M)


Abstract

A study was conducted from August 2000 to August 2001 to characterize the influence of fertilizer use from different nitrogen sources on the quality of drainage water from 11 subsurface tile drains and 7 surface field ditches in a North Carolina Coastal Plain watershed. Agricultural fields receiving commercial fertilizer (conventional sites), swine lagoon effluent (spray sites), and wastewater-treatment plant sludge (sludge site) in the Middle Swamp watershed were investigated. The ionic composition of drainage water in tile drains and ditches varied depending on fertilizer source type. The dominant ions identified in water samples from tile drains and ditches include calcium, magnesium, sodium, chloride, nitrate, and sulfate, with tile drains generally having lower pH, low or no bicarbonates, and higher nitrate and chloride concentrations. Based on fertilizer source type, median nitrate-nitrogen concentrations were significantly higher at spray sites (32.0 milligrams per liter for tiles and 8.2 milligrams per liter for ditches) relative to conventional sites (6.8 milligrams per liter for tiles and 2.7 milligrams per liter for ditches). The median instantaneous nitrate-nitrogen yields also were significantly higher at spray sites (420 grams of nitrogen per hectare per day for tile drains and 15.6 grams of nitrogen per hectare per day for ditches) relative to conventional sites (25 grams of nitrogen per hectare per day for tile drains and 8.1 grams of nitrogen per hectare per day for ditches). The tile drain site where sludge is applied had a median nitrate-nitrogen concentration of 10.5 milligrams per liter and a median instantaneous nitrate-nitrogen yield of 93 grams of nitrogen per hectare per day, which were intermediate to those of the conventional and spray tile drain sites. Results from this study indicate that nitrogen loadings and subsequent edge-of-field nitrate-nitrogen yields through tile drains and ditches were significantly higher at sites receiving applications of swine lagoon effluent compared to sites receiving commercial fertilizer.

Table of Contents

Figures

  1. Map showing locations of study sites in the Middle Swamp watershed in the Neuse River basin, North Carolina
  2. Piper diagrams showing ionic composition of water grouped by (A) conventional ditches and tiles, and the sludge tile, and (B) spray ditches and tiles in the Middle Swamp watershed
  3. Piper diagrams showing ionic composition of water grouped by (A) conventional ditches and spray ditches, and (B) conventional tiles, spray tiles, and the sludge tile in the Middle Swamp watershed
  4. 4 7. Graphs showing:
    1. Temporal distribution of nitrate concentrations and yields at selected (A) conventional sites and (B) spray sites in the Middle Swamp watershed
    2. Relation of nitrate concentration and discharge at (A) tile sites and (B) ditch sites in the Middle Swamp watershed
    3. Relation of median nitrate yield and soil drainage class for tile sites in the Middle Swamp watershed
    4. (A) Nitrate concentrations and (B) instantaneous yields grouped by site and fertilizer type in the Middle Swamp watershed

Tables

  1. Drainage area and soil characteristics for study sites in the Middle Swamp watershed in the Neuse River basin, North Carolina
  2. Discharge and nitrate data at study sites in the Middle Swamp watershed, August 2000 to August 2001
  3. Summary of nitrate and discharge data by site type and fertilizer type in the Middle Swamp watershed, August 2000 to August 2001

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U.S. Geological Survey
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Raleigh, North Carolina 27607
(919) 571-4000
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Denver, CO 80225
 
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