Nitrate transport on a sandy coastal plain soil underlain by plinthite.
Hubbard R.K. | Leonard R.A. | Johnson A.W.
Transport of nitrate (NO3-N) by surface runoff, shallow subsurface flow, and leaching during 1988-89 was determined on a sandy Coastal Plain soil having plinthic subsoil materials. The study was conducted on a small (0.34 ha) instrumented watershed. Nitrate concentrations were measured in surface runoff, shallow subsurface flow, soil samples collected from the upper 30 cm of the root zone, and water samples collected from shallow and deep wells. The study showed that most of the NO3-N leached from the upper 30 cm of the root zone within 1.5 months after N application, given a total rainfall of 200 mm or more. Surface runoff NO3-N concentrations and loads were small, with monthly loads not exceeding 0.3 kg/ha. Nitrate concentrations in shallow groundwater (0.9 to 1.8 m) during the sweet corn growing season reflected applied N. with values ranging from 11 to 19 mg/L. Applied N was also reflected in shallow subsurface flow during the spring months. Mean NO3-N concentrations in subsurface flow ranged from 3.9 to 14.1 mg/L, while monthly loads ranged from 0.1 to 9.2 kg/ha. The study indicated that some NO3-N is being lost by vertical water movement in plinthic Coastal Plain soils towards deeper groundwater, and that this loss pathway should be of environmental concern.
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