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This article in SSSAJ

  1. Vol. 46 No. 4, p. 748-750
    Received: Jan 22, 1982
    Accepted: Mar 17, 1982

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Nitrate Reduction in Spartina Alterniflora Marsh Soil1

  1. C. J. Smith,
  2. R. D. DeLaune and
  3. W. H. Patrick Jr.2



The transformation of nitrate (NO-3) was investigated in flooded Louisiana Gulf Coast salt marsh soll. Nitrate formed in the aerobic zone of the soil is readily reduced in the deeper anoxic zone by dissimilatory and/or assimilatory processes. The experiments were conducted in soil cores 15 cm in diameter by 12 to 15 cm in depth. 15N-labelled NO-3 at 0.6 g N m−2 was administered in either a single injection into the floodwater or in repeated small injections below the sediment-water interface. For the single application experiment, 14% of the 15N remained in the system; 4% NH+4-N and 10% organic N. This implies dissimilatory reduction, with NO-3 being reduced to NH+4 prior to formation of organic N. Fifty separate applications increased the recovery of 15N in the NH+4-N and organic N pool to 52%. The latter procedure more nearly reproduces the low steady-state concentration of NO-3 observed in salt marsh soil; the increased recovery suggests that the internal inorganic-N cycling in these soils may be more efficient than previously reported.

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