Contributions from different microbial processes to N2O emission from soil under different moisture regimes

Webster, Elizabeth; Hopkins, D. W.

doi:10.1007/s003740050120

Cited by 36 publications

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“…The fresh plant material and the post-harvest residues decomposed at the same rate, even with the wider C:N ratios of the post-harvest residues than of the fresh plant material (Table 2). This lack of difference in decomposition rate may be related to the relatively low C:N ratio of the soil (11.2) and the fact that N cycling processes are relatively rapid in this soil (Webster and Hopkins 1996) and, therefore, there was probably an abundant supply of available N for microorganisms. As the fresh plant residues and the post-harvest residues decomposed at the same rate in the laboratory experiment, hereafter we will refer to both of these as "young residues" unless a distinction is being made between them.…”

Section: Carbon Mineralizationmentioning

confidence: 98%

Decomposition of residues and loss of the δ-endotoxin from transgenic (Bt) corn (Zea mays L.) in soil

Hopkins

Gregorich

2005

Can. J. Soil. Sci.

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. 2005. Decomposition of residues and loss of the δ-endotoxin from transgenic (Bt) corn (Zea mays L.) in soil. Can. J. Soil Sci. 85: 19-26. Corn and other crops genetically modified to express the insecticidal δ-endotoxin from Bacillus thuringiensis (Bt) are grown widely across north America. Studies have shown that the δ-endotoxin can be stabilised on soil colloids where its activity is retained, but reports of direct ecological effects of the δ-endotoxin on soil processes are limited. We have determined the concentrations of the δ-endotoxin in organic residues from Bt-corn plants at increasing stages of ageing and decay, and the subsequent decomposition in soil of these residues and the δ-endotoxin in them. The δ-endotoxin concentrations declined from 6.8 µg g -1 in the fresh plant material, to 0.82 µg g -1 in the post-harvest residues collected in the fall, and to 0.026 µg g -1 in the residues collected from soil surface the following spring. The concentration of δ-endotoxin in buried residues collected in the spring was not significantly different from zero. When incubated in soil in the laboratory over 84 d, the δ-endotoxin decomposed more rapidly than bulk plant C by factors of 1.85 for the fresh plant materials and 3.21 for the post-harvest residues. Within 14 d of incubation, the δ-endotoxin concentration in the residues collected at the soil surface was below the limit of detection. We contrasted the laboratory decomposition data with data from a field experiment to estimate the period that the δ-endotoxin in corn residues may survive in the field. Based on estimates derived from this comparison, we predict that following an October harvest in eastern Ontario the δ-endotoxin would fall below the detection threshold during November for post-harvest residues. Since stabilisation of the δ-endotoxin on soil colloids depends on it surviving (i.e., not being decomposed) for long enough to be released from the plant residue matrix and come into proximity with colloid surfaces, the rapid decay of the δ-endotoxin suggests that only a small fraction of the δ-endotoxin from post-harvest residues persists long enough to become stabilised in the field. Des études ont montré que la δ-endotoxine se stabilise sur les colloïdes du sol et garde son activité, mais on sait peu de choses au sujet de son incidence écologique sur les processus du sol. Les auteurs ont établi la concentration de δ-endotoxine dans les résidus organiques de plants de maïs Bt à différents stades de vieillissement et de pourrissement ainsi que la décomposition subséquente de ces résidus et de la δ-endotoxine dans le sol. La concentration de δ-endotoxine passe de 6,8 µg par gramme dans les tissus végétaux frais à 0,82 µg par gramme dans les résidus post-messianiques recueillis à l'automne puis à 0,026 µg par gramme dans ceux prélevés à la surface du sol le printemps suivant. La concentration de δ-endotoxine dans les résidus enfouis, prélevés au printemps, ne diffère pas significativement de zéro. Incubée pendant 84 jours dans le sol en laboratoire, ...

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Section: Carbon Mineralizationmentioning

confidence: 98%

Decomposition of residues and loss of the δ-endotoxin from transgenic (Bt) corn (Zea mays L.) in soil

Hopkins

Gregorich

2005

Can. J. Soil. Sci.

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“…Total organic N, being higher in the A horizon than the two subsoil horizons, can be transformed to nitrate and thus contributed to higher N 2 O production by nitrification because A horizon had comparatively higher (WFPS 80%) aeration than B and C horizons (WFPS 85-88%). High N 2 O/(N 2 O+N 2 ) ratios are the characteristic of fairly well-aerated soil, in which N 2 O can easily diffuse away, and thus is not further reduced to N 2 by denitrifying organisms (Webster and Hopkins, 1996) and also the presence of high NO 3 -in top soil can decrease further reduction of N 2 O to N 2 (Bandibas, et al, 1994). Schlegel (1992) explained this phenomenon by stating that …”

Section: N 2 O Mole Fractions (N 2 O/(n 2 O+n 2 ) At Various Soil Depthsmentioning

confidence: 99%

Denitrification potential in subsoils: A mechanism to reduce nitrate leaching to groundwater

Jahangir

Khalil

Johnston

et al. 2012

Agriculture, Ecosystems & Environment

145

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“…During the dissimilative reduction of nitrate, N 2 O is produced via the nonspecific reaction of nitrate reductase with nitrite (38). During nitrification, N 2 O can be produced as a side product when ammonia is oxidized to nitrite via the intermediate hydroxylamine (6,34,44).…”

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confidence: 99%

N ₂ O-Producing Microorganisms in the Gut of the Earthworm Aporrectodea caliginosa Are Indicative of Ingested Soil Bacteria

Ihssen

Horn

Matthies

et al. 2003

Appl Environ Microbiol

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The main objectives of this study were (i) to determine if gut wall-associated microorganisms are responsible for the capacity of earthworms to emit nitrous oxide (N 2 O) and (ii) to characterize the N 2 O-producing bacteria of the earthworm gut. The production of N 2 O in the gut of garden soil earthworms (Aporrectodea caliginosa) was mostly associated with the gut contents rather than the gut wall. Under anoxic conditions, nitrite and N 2 O were transient products when supplemental nitrate was reduced to N 2 by gut content homogenates. In contrast, nitrite and N 2 O were essentially not produced by nitrate-supplemented soil homogenates. The most probable numbers of fermentative anaerobes and microbes that used nitrate as a terminal electron acceptor were approximately 2 orders of magnitude higher in the earthworm gut than in the soil from which the earthworms originated. The fermentative anaerobes in the gut and soil displayed similar physiological functionalities. A total of 136 N 2 O-producing isolates that reduced either nitrate or nitrite were obtained from high serial dilutions of gut homogenates. Of the 25 representative N 2 O-producing isolates that were chosen for characterization, 22 isolates exhibited >99% 16S rRNA gene sequence similarity with their closest cultured relatives, which in most cases was a soil bacterium, most isolates were affiliated with the gamma subclass of the class Proteobacteria or with the gram-positive bacteria with low DNA G؉C contents, and 5 isolates were denitrifiers and reduced nitrate to N 2 O or N 2 . The initial N 2 O production rates of denitrifiers were 1 to 2 orders of magnitude greater than those of the nondenitrifying isolates. However, most nondenitrifying nitrate dissimilators produced nitrite and might therefore indirectly stimulate the production of N 2 O via nitrite-utilizing denitrifiers in the gut. The results of this study suggest that most of the N 2 O emitted by earthworms is due to the activation of ingested denitrifiers and other nitrate-dissimilating bacteria in the gut lumen.

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Contributions from different microbial processes to N2O emission from soil under different moisture regimes

Cited by 36 publications

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Decomposition of residues and loss of the δ-endotoxin from transgenic (Bt) corn (Zea mays L.) in soil

Decomposition of residues and loss of the δ-endotoxin from transgenic (Bt) corn (Zea mays L.) in soil

Denitrification potential in subsoils: A mechanism to reduce nitrate leaching to groundwater

N ₂ O-Producing Microorganisms in the Gut of the Earthworm Aporrectodea caliginosa Are Indicative of Ingested Soil Bacteria

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Contributions from different microbial processes to N2O emission from soil under different moisture regimes

Cited by 36 publications

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Decomposition of residues and loss of the δ-endotoxin from transgenic (Bt) corn (Zea mays L.) in soil

Decomposition of residues and loss of the δ-endotoxin from transgenic (Bt) corn (Zea mays L.) in soil

Denitrification potential in subsoils: A mechanism to reduce nitrate leaching to groundwater

N 2 O-Producing Microorganisms in the Gut of the Earthworm Aporrectodea caliginosa Are Indicative of Ingested Soil Bacteria

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N ₂ O-Producing Microorganisms in the Gut of the Earthworm Aporrectodea caliginosa Are Indicative of Ingested Soil Bacteria