129-16
Nitrification Responses of Ammonia-Oxidizing Bacteria and Archaea to Ammonia Additions in Cultivated and Uncultivated Soils.

Poster Number 1732

Monday, November 4, 2013
Tampa Convention Center, East Hall, Third Floor

Andrew Giguere1, Anne Taylor1, David D. Myrold1 and Peter J. Bottomley2, (1)Department of Crop and Soil Science, Oregon State University, Corvallis, OR
(2)Department of Crop and Soil Science & Department of Microbiology, Oregon State University, Corvallis, OR
Ammonia (NH3) oxidization is the first and rate-limiting step in nitrification, and is carried out by both NH3-oxidizing archaea (AOA) and NH3-oxidizing bacteria (AOB). While both organisms are present in most soils, it is unknown what controls their relative contributions to nitrification. Recently in our laboratory we have shown that the aliphatic 1-octyne can discriminate between the contributions of AOB (octyne-sensitive) and of AOA (octyne-resistant) to soil nitrification. We investigated the nitrification responses of AOA and AOB in paired cultivated and uncultivated soils from four different regions across Oregon.  We determined the nitrification responses of these soils to a range of additions of anhydrous NH3 (1-40 µmol NH3 g-1 soil) in the presence and absence of 1-octyne.  Uncultivated soils generally needed lower NH3 additions (2-5 µmol NH3 g-1 soil) to reach saturating nitrification rates than did cultivated soils (6-22 µmol NH3 g-1 soil).  In uncultivated soils, AOA were involved in NH3 oxidation at all NH3 additions, while AOB contributed to nitrification in only two of the four uncultivated soils and only after addition of > 2 µmol NH3 g-1 soil. Cultivated soils showed no measurable contribution from AOA at any NH3 addition, and all activity was octyne sensitive and attributed to AOB. The octyne sensitive nitrification rates in the two uncultivated soils saturated at lower rates of NH3 addition  (0.5-0.7 µmol NO2- + NO3- g-1 soil day-1) than the AOB nitrification rates in cultivated soils (0.6-1.5 µmol NO2- + NO3 g-1 soil day-1). This whole soil microcosm approach with and without octyne treatment is providing useful insights into the effects of cultivation and fertilization on nitrification by soil-borne AOA and AOB.
See more from this Division: SSSA Division: Soil Biology & Biochemistry
See more from this Session: Student Poster Competition

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