| View Larger Image | Nitrous oxide production by nitrification and denitrification in soil aggregates as affected by O"2 concentration [An article from: Soil Biology and Biochemistry] | Digitalby K. Khalil (Author), B. Mary (Author), P. Renault (Author)
| List Price: | $8.95 | | | Available: | Available for download now |
| | Binding: | Digital | | Publisher: | Elsevier | | Publication Date: | April 01, 2004 |
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Product Description
This digital document is a journal article from Soil Biology and Biochemistry, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.Description: Nitrous oxide emitted by soils can be produced either by denitrification in anoxic conditions or by nitrification in presence of O"2. The relative importance of the two processes, particularly under varied partial pressures of O"2, is not always known. This paper focuses on the influence of O"2 concentration on N"2O production by nitrification and denitrification in an arable Orthic Luvisol. Soil aggregates (2-3 mm size), water unsaturated, received 116 mg Nkg^-^1 as ammonium sulphate labelled with ^1^5N and were incubated during 14 days at different O"2 partial pressures: 0, 0.35, 0.76, 1.5, 4.3 and 20.4kPa. A ^1^5N tracing technique was used to quantify nitrification and denitrification rates. ^1^5N"2O and ^1^5N"2 were measured. Oxygen pressure appeared to strongly influence both nitrification and denitrification rates and also N"2O emissions. Nitrification rates were reduced by a factor of 6-9 when O"2 decreased from 20.4 to 0.35kPa. They were highly correlated with O"2 consumption rates. Denitrification mainly occurred in complete anoxic conditions. The proportion of N"2O emitted by denitrification was estimated by two independent methods: one based on ^1^5N tracing using isotope composition of NH"4, NO"3 and N"2O, the other based on the measurement of the ^1^5N"2O:^1^5N"2 ratio. The two methods gave close results. The highest N"2O emissions were obtained under complete anoxic conditions and were due to denitrification. However, N"2O emissions almost as important were obtained at day 14 with 1.5kPa O"2 pressure, and they were due to nitrification. Nitrification was the main source of N"2O at O"2 concentrations greater than 0.35kPa. The amounts of N"2O-N emitted by nitrification were linearly related to the amounts of N nitrified, but the slope of the regression was highly dependent on O"2 concentration: it varied from 0.16 to 1.48% when O"2 concentration was reduced from 20.4 to 0.76kPa. Emissions of N"2O by nitrification may then be quite significant if nitrification occurs at a reduced O"2 concentration. |
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