Patterns Observed for the Oxidation of Ammonium to Nitrate by Soil Organisms

Morrill, L. G.; Dawson, J. E.

doi:10.2136/sssaj1967.03615995003100060017x

Cited by 122 publications

(43 citation statements)

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“…Under unfertilized conditions, the mean AOB population sizes were 7.1 ϫ 10 6 and 5.5 ϫ 10 6 cells/g of dry soil in microcosms and field samples, respectively. Our AOB population size estimates were several orders of magnitude greater than AOB population sizes in agricultural soils reported on the basis of most-probable-number (MPN) methods (13,25,32) and FISH with the microcolony method (17). This discrepancy was not surprising because the MPN method and the FISH-microcolony method count only culturable cells active under MPN assay conditions or on the membrane used for microcolony formation.…”

Section: Discussioncontrasting

confidence: 61%

Application of Real-Time PCR To Study Effects of Ammonium on Population Size of Ammonia-Oxidizing Bacteria in Soil

Okano

Hristova

Leutenegger³

et al. 2004

Appl Environ Microbiol

382

201

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Ammonium oxidation by autotrophic ammonia-oxidizing bacteria (AOB) is a key process in agricultural and natural ecosystems and has a large global impact. In the past, the ecology and physiology of AOB were not well understood because these organisms are notoriously difficult to culture. Recent applications of molecular techniques have advanced our knowledge of AOB, but the necessity of using PCR-based techniques has made quantitative measurements difficult. A quantitative real-time PCR assay targeting part of the ammoniamonooxygenase gene (amoA) was developed to estimate AOB population size in soil. This assay has a detection limit of 1.3 ؋ 10 5 cells/g of dry soil. The effect of the ammonium concentration on AOB population density was measured in soil microcosms by applying 0, 1.5, or 7.5 mM ammonium sulfate. AOB population size and ammonium and nitrate concentrations were monitored for 28 days after (NH 4 ) 2 SO 4 application. AOB populations in amended treatments increased from an initial density of approximately 4 ؋ 10 6 cells/g of dry soil to peak values (day 7) of 35 ؋ 10 6 and 66 ؋ 10 6 cells/g of dry soil in the 1.5 and 7.5 mM treatments, respectively. The population size of total bacteria (quantified by real-time PCR with a universal bacterial probe) remained between 0.7 ؋ 10 9 and 2.2 ؋ 10 9 cells/g of soil, regardless of the ammonia concentration. A fertilization experiment was conducted in a tomato field plot to test whether the changes in AOB density observed in microcosms could also be detected in the field. AOB population size increased from 8.9 ؋ 10 6 to 38.0 ؋ 10 6 cells/g of soil by day 39. Generation times were 28 and 52 h in the 1.5 and 7.5 mM treatments, respectively, in the microcosm experiment and 373 h in the ammonium treatment in the field study. Estimated oxidation rates per cell ranged initially from 0.5 to 25.0 fmol of NH 4 ؉ h ؊1 cell ؊1 and decreased with time in both microcosms and the field. Growth yields were 5.6 ؋ 10 6 , 17.5 ؋ 10 6 , and 1.7 ؋ 10 6 cells/mol of NH 4 ؉ in the 1.5 and 7.5 mM microcosm treatments and the field study, respectively. In a second field experiment, AOB population size was significantly greater in annually fertilized versus unfertilized soil, even though the last ammonium application occurred 8 months prior to measurement, suggesting a long-term effect of ammonium fertilization on AOB population size.Ammonium oxidation by autotrophic ammonia-oxidizing bacteria (AOB) is a key process in agricultural and natural ecosystems, with a large global impact. The product of this process, nitrite, is immediately oxidized by nitrite-oxidizing bacteria to nitrate, a nitrogen form susceptible to leaching. Nitrogen leaching can lead to groundwater pollution and surface and groundwater eutrophication. Nitrous oxide and nitric oxide, by-products of ammonia oxidation, contribute to the greenhouse effect and ozone layer depletion. On a local scale, loss of nitrate to groundwater and nitrous oxide and nitric oxide to the atmosphere reduces the amount of nitrogen available ...

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Section: Discussioncontrasting

confidence: 61%

Application of Real-Time PCR To Study Effects of Ammonium on Population Size of Ammonia-Oxidizing Bacteria in Soil

Okano

Hristova

Leutenegger³

et al. 2004

Appl Environ Microbiol

382

201

View full text Add to dashboard Cite

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“…Thus, substantial NO 3 -losses via leaching or denitrification were unlikely during this time. The slow nitrification might be attributable to the ongoing inhibitory effects of low pH (5.06-5.33) in the top 20 cm of soil (Morrill and Dawson 1967;Sahrawat 2008). In the subsequent two months (24 December 2012 to 1 March 2013) when heavy rainfall and the majority of high N 2 O emission episodes occurred, substantial loss of N was most likely to have occurred as a result of leaching or denitrification.…”

Section: Processes and Factors Affecting Soil Mineral N Dynamics And mentioning

confidence: 99%

Nitrous oxide emission and fertiliser nitrogen efficiency in a tropical sugarcane cropping system applied with different formulations of urea

et al. 2016

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Abstract. Nitrous oxide (N 2 O) emissions from sugarcane cropped soils are usually high compared with those from other arable lands. Nitrogen-efficient management strategies are needed to mitigate N 2 O emissions from sugarcane farming whilst maintaining productivity and profitability. A year-long field experiment was conducted in wet tropical Australia to assess the efficacy of polymer-coated urea (PCU) and nitrification inhibitor (3,4-dimethylpyrazole phosphate)-coated urea (NICU). Emissions of N 2 O were measured using manual and automatic gas sampling chambers in combination. The nitrogen (N) release from PCU continued for >5-6 months, and lower soil NO 3 -contents were recorded for !3 months in the NICU treatments compared with the conventional urea treatments. The annual cumulative N 2 O emissions were high, amounting to 11.4-18.2 kg N 2 O-N ha -1 . In contrast to findings in most other cropping systems, there were no significant differences in annual N 2 O emissions between treatments with different urea formulations and application rates (0, 100 and 140 kg N ha -1 ). Daily variation in N 2 O emissions at this site was driven predominantly by rainfall. Urea formulations did not significantly affect sugarcane or sugar yield at the same N application rate. Decreasing fertiliser application rate from the recommended 140 kg N ha -1 to 100 kg N ha -1 led to a decrease in sugar yield by 1.3 t ha -1 and 2.2 t ha -1 for the conventional urea and PCU treatments, respectively, but no yield loss occurred for the NICU treatment. Crop N uptake also declined at the reduced N application rate with conventional urea, but not with the PCU and NICU. These results demonstrated that substituting NICU for conventional urea may substantially decrease fertiliser N application from the normal recommended rates whilst causing no yield loss or N deficiency to the crop. Further studies are required to investigate the optimal integrated fertiliser management strategies for sugarcane production, particularly choice of products and application time and rates, in relation to site and seasonal conditions.

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“…Accumulation of nitrite during nitrification is associated with alkaline pH values (9, 10, 1l). As little as 15 ppm have been shown to be toxic to lettuce (11).…”

Section: In'iroductionmentioning

confidence: 99%