![N"2O emissions and product ratios of nitrification and denitrification as affected by freezing and thawing [An article from: Soil Biology and Biochemistry]](https://www.ebooknetworking.net/books/B00/0PA/bigB000PAUXN4.jpg)
N"2O emissions and product ratios of nitrification and denitrification as affected by freezing and thawing [An article from: Soil Biology and Biochemistry]
Book Details
PublisherElsevier
ISBN / ASINB000PAUXN4
ISBN-13978B000PAUXN2
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Sales Rank99,999,999
MarketplaceUnited States 🇺🇸
Description
This digital document is a journal article from Soil Biology and Biochemistry, published by Elsevier in 2006. 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:
Agricultural soils contribute significantly to atmospheric nitrous oxide (N"2O). A considerable part of the annual N"2O emission may occur during the cold season, possibly supported by high product ratios in denitrification (N"2O/(N"2+N"2O)) and nitrification (N"2O-N/(NO"3^--N+NO"2^--N)) at low temperatures and/or in response to freeze-thaw perturbation. Water-soluble organic materials released from frost-sensitive catch crops and green manure may further increase winter emissions. We conducted short-term laboratory incubations under standardized moisture and oxygen (O"2) conditions, using nitrogen (N) tracers (^1^5N) to determine process rates and sources of emitted N"2O after freeze-thaw treatment of soil or after addition of freeze-thaw extract from clover. Soil respiration and N"2O production was stimulated by freeze-thaw or addition of plant extract. The N"2O emission response was inversely related to O"2 concentration, indicating denitrification as the quantitatively prevailing process. Denitrification product ratios in the two studied soils (pH 4.5 and 7.0) remained largely unaltered by freeze-thaw or freeze-thaw-released plant material, refuting the hypothesis that high winter emissions are due to frost damage of N"2O reductase activity. Nitrification rates estimated by nitrate (NO"3^-) pool enrichment were 1.5-1.8@mgNO"3-Ng^-^1dwsoild^-^1 in freeze-thaw-treated soil when incubated at O"2 concentrations above 2.3vol% and one order of magnitude lower at 0.8vol% O"2. Thus, the experiments captured a situation with severely O"2-limited nitrification. As expected, the O"2 stress at 0.8vol% resulted in a high nitrification product ratio (0.3gg^-^1). Despite this high product ratio, only 4.4% of the measured N"2O accumulation originated from nitrification, reaffirming that denitrification was the main N"2O source at the various tested O"2 concentrations in freeze-thaw-affected soil. N"2O emission response to both freeze-thaw and plant extract addition appeared strongly linked to stimulation of carbon (C) respiration, suggesting that freeze-thaw-induced release of decomposable organic C was the major driving force for N"2O emissions in our soils, both by fuelling denitrifiers and by depleting O"2. The soluble C (applied as plant extract) necessary to induce a CO"2 and N"2O production rate comparable with that of freeze-thaw was 20-30@mgCg^-^1soildw. This is in the range of estimates for over-winter soluble C loss from catch crops and green manure plots reported in the literature. Thus, freeze-thaw-released organic C from plants may play a significant role in freeze-thaw-related N"2O emissions.
Description:
Agricultural soils contribute significantly to atmospheric nitrous oxide (N"2O). A considerable part of the annual N"2O emission may occur during the cold season, possibly supported by high product ratios in denitrification (N"2O/(N"2+N"2O)) and nitrification (N"2O-N/(NO"3^--N+NO"2^--N)) at low temperatures and/or in response to freeze-thaw perturbation. Water-soluble organic materials released from frost-sensitive catch crops and green manure may further increase winter emissions. We conducted short-term laboratory incubations under standardized moisture and oxygen (O"2) conditions, using nitrogen (N) tracers (^1^5N) to determine process rates and sources of emitted N"2O after freeze-thaw treatment of soil or after addition of freeze-thaw extract from clover. Soil respiration and N"2O production was stimulated by freeze-thaw or addition of plant extract. The N"2O emission response was inversely related to O"2 concentration, indicating denitrification as the quantitatively prevailing process. Denitrification product ratios in the two studied soils (pH 4.5 and 7.0) remained largely unaltered by freeze-thaw or freeze-thaw-released plant material, refuting the hypothesis that high winter emissions are due to frost damage of N"2O reductase activity. Nitrification rates estimated by nitrate (NO"3^-) pool enrichment were 1.5-1.8@mgNO"3-Ng^-^1dwsoild^-^1 in freeze-thaw-treated soil when incubated at O"2 concentrations above 2.3vol% and one order of magnitude lower at 0.8vol% O"2. Thus, the experiments captured a situation with severely O"2-limited nitrification. As expected, the O"2 stress at 0.8vol% resulted in a high nitrification product ratio (0.3gg^-^1). Despite this high product ratio, only 4.4% of the measured N"2O accumulation originated from nitrification, reaffirming that denitrification was the main N"2O source at the various tested O"2 concentrations in freeze-thaw-affected soil. N"2O emission response to both freeze-thaw and plant extract addition appeared strongly linked to stimulation of carbon (C) respiration, suggesting that freeze-thaw-induced release of decomposable organic C was the major driving force for N"2O emissions in our soils, both by fuelling denitrifiers and by depleting O"2. The soluble C (applied as plant extract) necessary to induce a CO"2 and N"2O production rate comparable with that of freeze-thaw was 20-30@mgCg^-^1soildw. This is in the range of estimates for over-winter soluble C loss from catch crops and green manure plots reported in the literature. Thus, freeze-thaw-released organic C from plants may play a significant role in freeze-thaw-related N"2O emissions.
