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Journal of Environmental Quality Abstract -

Nitrate Reduction and Nitrite Utilization by Nitrifiers in an Unsaturated Hanford Sandy Loam1


This article in JEQ

  1. Vol. 4 No. 2, p. 179-182
    Received: Apr 25, 1974

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  1. M. G. Volz,
  2. L. W. Belser,
  3. M. S. Ardakani and
  4. A. D. McLaren2



In order to discern any relationship between added nitrate and microbial growth in a field plot, a Hanford sandy loam was infiltrated for 5 weeks at a rate of 5 cm day−1 with a solution containing 100 ppm -N and 1.25 meq/liter Cl as KNO3 and CaCl2 respectively. Nitrate-N, NO2-N and Cl concentrations in soil solution were determined and corresponding counts of nitrate reducers, denitrifiers, and NH4+- and NO2-oxidizer populations were made.

Ratios of measured to applied concentrations for both NO3-N and Cl were nearly identical in all solution samples taken from the unsaturated soil profile, i.e., nitrate reduction was not pronounced and NO2-N was less than 1 ppm.

Nitrate reducer populations (6x104–6x105/g soil) were always larger than those of denitrifiers (3x103–3x104/g) and varied little with time and depth. Ammonium oxidizers (101–105/g) generally decreased with depth. In contrast, NO2 oxidizers (101–3x106/g) varied markedly with time at all depths. An increase in numbers of NO2 oxidizers, after 2 to 3 weeks, at a depth of 60 cm, is attributed to NO2 produced by reduction of NO3 at anoxic microsites within the profile. Evidently, a cyclic oxidation and reduction of nitrite and nitrate, occurring simultaneously, is responsible for growth of nitrite oxidizers in the profile.

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