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This article in SSSAJ

  1. Vol. 53 No. 5, p. 1608-1611
     
    Received: Apr 28, 1988


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doi:10.2136/sssaj1989.03615995005300050056x

A Dilute Medium to Determine Population Size of Ammonium Oxidizers in Forest Soils

  1. Jennifer M. Donaldson  and
  2. Gray S. Henderson
  1. Natl. Res. Counc., US-EPA, 200 S.W. 35th St., Corvallis, OR 97333
    School of Forestry, Fisheries and Wildlife, Agric. Bldg., Univ. of Missouri, Columbia, MO 65211

Abstract

Abstract

Incubation experiments using soils from mixed oak (Quercus sp.) stands showed accumulation of nitrate but standard most probable number (MPN) assays showed no NH4-oxidizing bacteria were present. This led to a preliminary conclusion that nitrification in these soils must be heterotrophic. However, further incubation studies indicated that NH4-N concentrations in standard MPN medium were too high for autotrophic NH4 oxidizers that are adapted to soils with low NH4-N levels and exhibit low activities. Therefore, media with lower NH4-N concentrations were tested against the standard MPN medium. Each medium was tested using both 1 mM phosphate buffer and deionized water as diluent to examine responses to small changes in buffer capacity. A 0.1 × medium used with deionized water diluent was found to best estimate populations of low-activity NH4-oxidizing bacteria present in soils with low NH4-N concentrations.

Contribution of the Missouri Agric. Exp. Stn. Journal no. 10760.

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