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  • Articles  (86)
  • Denitrification  (86)
  • Springer  (86)
  • American Chemical Society (ACS)
  • Geosciences  (86)
  • 1
    ISSN: 1432-0789
    Keywords: Denitrification ; Acetylene inhibition technique ; Grassland ; Lolium perenne ; Animal slurry ; Dicyandiamide ; Nitrification inhibition ; Ammonium nitrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In a field experiment, the effect of animal slurry, (with and without the nitrification inhibitor dicyandiamide on total denitrification losses estimated by the C2H2 inhibition technique was measured over 2 years (1989–1990). During this period, four different plots (each with four replicates) were fertilized six times with 150 kg N ha-1 in the form of cattle-pig slurry or NH4NO3. Soil samples (0–20 cm) were analysed at regular intervals for NH inf4 sup+ and NO inf3 sup− concentrations. The soil water content was determined gravimetrically. During the first year (1989) total denitrification losses from unfertilized, mineral-fertilized, and animal slurry-amended plots (with or without dicyandiamide) were estimated as 0.2, 3.1, 0.7, and 0.6 kg N ha-1, respectively. During the second year (1990) the denitrification losses were 0.4, 1.3, 0.7, and 0.7 kg N ha-1, respectively. There was a clear relationship between the NO inf3 sup− concentration or soil water content and the denitrification rate. The results are siteund experiment-specific and cannot be generalized so far.
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  • 2
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    Biology and fertility of soils 2 (1986), S. 15-21 
    ISSN: 1432-0789
    Keywords: Denitrification ; Aerobic respiration ; Water potential ; Soil respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The influence of soil moisture on denitrification and aerobic respiration was studied in a mull rendzina soil. N2O formation did not occur below −30 kPa matric water potential (Ψm), above 0.28 air-filled porosity (a) and below 0.55 fractional water saturation (Θv/PV ≙ volumetric water content/total pore volume). Half maximum rates of N2O production and O2 consumption were obtained between Ψm = −1.2 and −12 kPa,a = 0.05 and 0.23, and Θv/PV = 0.63 and 0.92. No oxygen consumption was measured at Θv/PC ≧ 1.17. O2 uptake and denitrification occurred simultaneously arounda = 0.10 (at Ψm = −10 kPa and Θv/PV = 0.81) at mean rates of 3.5 µl O2 and 0.3 µl N2 h−1g−1 soil. Undisturbed, field-moist soil saturated with nitrate solution showed constant consumption and production rates, respectively, of 0.6 µl O and 0.22 µl N2O h−1g−1 soil, whereas the rates of air-dried remoistened soil were at least 10 times these values. The highest rates obtained in remoistened soil amended with glucose and nitrate were 130 µl O2 and 27 µl N2O h−1g−1 soil.
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  • 3
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    Biology and fertility of soils 24 (1997), S. 111-117 
    ISSN: 1432-0789
    Keywords: Denitrification ; Acetylene inhibition method ; Nitrous oxide release ; Soilless plant culture ; Root growth ; Cucumis sativus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Denitrification measurements by means of the acetylene inhibition method require a continuous presence of acetylene to block the microbial reduction of N20 to N2. To examine the effect of such steady exposures on the growth of plants, roots of cucumber and tomato seedlings were treated with different acetylene concentrations. Acetylene concentrations of ≥1 vol% in the gas phase, which were necessary for complete inhibition of N2 formation, led to a significant retardation of root growth. This was partly due to trace amounts of ethylene contained in the acetylene gas which could not be removed with the usual prescrubbing through a sulfuric acid train. As a result of the growth impairment, oxygen consumption in the root zone decreased after 4 days of exposure. In order to avoid these side effects, the denitrification measurements in soilless cultures were performed on individual plants over a limited period of 2–3 days. The flow-through chamber method proved to be suitable for determining the gaseous N losses in a closed-loop system. It avoided greater air variations from the environmental conditions (substrate temperature, airflow and plant composition) and excluded errors in measurement caused by injury to roots and spatial variability of denitrification activity in the root medium. For exact estimation of the gaseous N losses, preceding 24-h acetylene fumigation was necessary. Subsequently at least three gas samples had to be taken throughout the day, because the N2O+N2 emissions were subject to a pronounced diurnal variability.
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  • 4
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    Biology and fertility of soils 2 (1986), S. 147-149 
    ISSN: 1432-0789
    Keywords: Denitrification ; N2O ; Earthworm casts ; Respiration ; Lumbricus terrestris ; Medicago sativa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Earthworms (Lumbricus terrestris L.) were cultured in the laboratory and fed on lucerne (Medicago sativa L.). Denitrification rates in the surface casts and the surrounding soil were quantified using C2H2-inhibition of nitrous oxide reductase. The investigation also included determination of the N2O-formation by nitrification as well as CO2-formation as a measure of respiration. The denitrification rates of wet earthworm casts were found to be significantly higher than those occurring in wet samples from the soil. The low N2O-formation observed seemed to be due to denitrification. Respiration was higher in casts, indicating higher oxygen demand which resulted in more anaerobic conditions. The energy supply was probably better in casts compared with the surrounding soil.
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  • 5
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    Biology and fertility of soils 31 (2000), S. 427-435 
    ISSN: 1432-0789
    Keywords: Key words Rice ; Nitrification ; Denitrification ; Rhizosphere ; Microelectrode
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  N turnover in flooded rice soils is characterized by a tight coupling between nitrification and denitrification. Nitrification is restricted to the millimetre-thin oxic surface layer while denitrification occurs in the adjacent anoxic soil. However, in planted rice soil O2 released from the rice roots may also support nitrification within the otherwise anoxic bulk soil. To locate root-associated nitrification and denitrification we constructed a new multi-channel microelectrode that measures NH4 +, NO2 –, and NO3 – at the same point. Unfertilized, unplanted rice microcosms developed an oxic-anoxic interface with nitrification taking place above and denitrification below ca. 1 mm depth. In unfertilized microcosms with rice plants, NH4 +, NO2 – and NO3 – could not be detected in the rhizosphere. Assimilation by the rice roots reduced the available N to a level where nitrification and denitrification virtually could not occur. However, a few hours after injecting (NH4)2HPO4 or urea, a high nitrification activity could be detected in the surface layer of planted microcosms and in a depth of 20–30 mm in the rooted soil. O2 concentrations of up to 150 μM were measured at the same depth, indicating O2 release from the rice roots. Nitrification occurred at a distance of 0–2 mm from the surface around individual roots, and denitrification occurred at a distance of 1.5–5.0 mm. Addition of urea to the floodwater of planted rice microcosms stimulated nitrification. Transpiration of the rice plants caused percolation of water resulting in a mass flow of NH4 + towards the roots, thus supporting nitrification.
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  • 6
    ISSN: 1432-0789
    Keywords: Phytotron study ; Corn plants ; Denitrification ; 15N balance ; N2 flux by 15N method ; N2O flux by gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Containers filled with soil mixed with potassium nitrate highly enriched in 15N were planted with corn (Zea mays L.) and kept in a phytotron under controlled conditions for 79 days. Soil water content was normally maintained at exactly 60% water-holding capacity (−33 kPa), but it was increased several times to 85% (−5 kPa) for short periods to favour denitrification. The soil headspace was sealed from the phytotron atmosphere and aerated by a continuous stream of air. Nitrous oxide emission was measured by estimating the N2O concentration differences in the air entering and leaving the containers. Emission of N2 was estimated by mass spectroscopy from changes in the N2 composition in the temporarily enclosed soil headspace. Both methods were carefully checked for accuracy by different tests. At specific times during the experiment the distribution of 15N between plants and soil was determined and a 15N balance established. Emission of N gases peaked at times of increased water content and reached maxima of 149 and 142 μg N pot−1 day−1 for N2O and N2, respectively. While N losses of 5% ± 2% were indicated by the 15N balance, only 1.1% ± 0.3% loss from 2.7 g applied N was estimated from the N2O and N2 measurements after 79 days. Possible reasons for these differences are discussed.
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  • 7
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    Biology and fertility of soils 7 (1989), S. 219-224 
    ISSN: 1432-0789
    Keywords: Soybean rhizobia ; Denitrification ; Nitrate ; Nitrous oxide ; Bradyrhizobium japonicum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Experiments to assess the ability of free-living cells of six strains of soybean rhizobia (Bradyrhizobium japonicum USDA 76, 94, 110, 122, 123, and 135) to denitrify nitrate in five soils showed that although some strains ofB. japonicum have the capacity to rapidly denitrify nitrate in soils under anaerobic conditions, it is unlikely that the numbers of soybean rhizobia commonly found under field conditions are sufficient to significantly influence either the extent or the products of denitrification in soil. It is our general conclusion that the advantages, if any, that the ability to denitrify conveys to rhizobia or to the rhizobia-legume symbiosis are not offset by increased losses of plant-available N when denitrifying strains of rhizobia are present as free-living cells in soil.
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  • 8
    ISSN: 1432-0789
    Keywords: Key words Grassland ; Denitrification ; N-fertiliser ; Nitrification ; Nitrous oxide emissions ; Global warming ; Ozone layer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The aim was to investigate the effects of different N fertilisers on nitrous oxide (N2O) flux from agricultural grassland, with a view to suggesting fertiliser practices least likely to cause substantial N2O emissions, and to assess the influence of soil and environmental factors on the emissions. Replicate plots on a clay loam grassland were fertilised with ammonium sulphate (AS), urea (U), calcium nitrate (CN), ammonium nitrate (AN), or cattle slurry supplemented with AN on three occasions in each of 2 years. Frequent measurements were made of N2O flux and soil and environmental variables. The loss of N2O-N as a percentage of N fertiliser applied was highest from the supplemented slurry (SS) treatment and U, and lowest from AS. The temporal pattern of losses was different for the different fertilisers and between years. Losses from U were lower than those from AN and CN in the spring, but higher in the summer. The high summer fluxes were associated with high water-filled pore space (WFPS) values. Fluxes also rose steeply with temperature where WFPS or mineral N values were not limiting. Total annual loss was higher in the 2nd year, probably because of the rainfall pattern: the percentage losses were 2.2, 1.4, 1.2, 1.1 and 0.4 from SS, U, AN, CN and AS, respectively. Application of U in the spring and AN twice in the summer in the 2nd year gave an average emission factor of 0.8% – lower than from application of either individual fertiliser. We suggest that similar varied fertilisation practices, modified according to soil and crop type and climatic conditions, might be employed to minimise N2O emissions from agricultural land.
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  • 9
    ISSN: 1432-0789
    Keywords: Key words Grassland ; Spring barley ; Nitrification inhibitor ; Nitrous oxide emission ; Denitrification ; Global warming ; Ozone layer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The aims of this study were to assess the effectiveness of the nitrification inhibitors dicyandiamide (DCD) and nitrapyrin on reducing emissions of nitrous oxide (N2O) following application of NH4 + or NH4 +-forming fertilisers to grassland and spring barley. DCD was applied to grassland with N fertiliser applications in April and August in 1992 and 1993, inhibiting N2O emissions by varying amounts depending on the fertiliser form and the time of application. Over periods of up to 2 months following each application of DCD, emissions of N2O were reduced by 58–78% when applied with urea (U) and 41–65% when applied with ammonium sulphate (AS). Annual emissions (April to March) of N2O were reduced by up to 58% and 56% in 1992–1993 and 1993–1994, respectively. Applying DCD to ammonium nitrate (AN) fertilised grassland did not reduce emissions after the April 1993 fertilisation, but emissions following the August application were reduced. Nitrapyrin was only applied once, with the April fertiliser applications in 1992, reducing N2O emissions over the following 12 months by up to 40% when applied with U. When N fertiliser was applied in June without DCD, the DCD applied in April was still partly effective; N2O emissions were reduced 50%, 60% and 80% as effectively as the emissions following the April applications, for AS in 1993, U in 1992 and 1993, respectively. In 1992 the persistence of an inhibitory effect was greater for nitrapyrin than for DCD, increasing after the June fertiliser application as overall emissions from U increased. There was no apparent reduction in effectiveness following repeated applications of DCD over the 2 years. N2O emissions from spring barley, measured only in 1993, were lower than from grassland. DCD reduced emissions from applied U by 40% but there was no reduction with AN. The results demonstrate considerable scope for reducing emissions by applying nitrification inhibitors with NH4 + or NH4 +-forming fertilisers; this is especially so for crops such as intensively managed grass where there are several applications of fertiliser nitrogen per season, as the effect of inhibitors applied in April persists until after a second fertiliser application in June.
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  • 10
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    Biology and fertility of soils 8 (1989), S. 219-226 
    ISSN: 1432-0789
    Keywords: Denitrification ; Acetylen inhibition technique ; 15N technique ; Organic residues ; Mineral fertilization ; Irrigation ; Temperate climate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Denitrification N losses can be determined by three methods. The first is by estimating the non-recovery of 15 N-labelled compounds (15N-balance method). Using this method, denitrification losses are deduced from the balance of an N budged (15N-labeled fertilizer), having accounted for transformations in soil, plant uptake, and leaching losses. The evolution of gaseous N from native soil N is not taken into account by this procedure. Studies on arable land with annual crops in the temperate zone have shown that of the fertilizer N applied, about 20–500% (10–70 kg N* ha−1) is not recovered at the end of the growth period. The second method of determining denitrification N losses is by in situ field measurement of 15 N 2 and 15 N 2 O production. Under this procedure, 15N-enriched N is applied to a plot and the denitrification N losses are determined by covering the soil. The method allows a quantitative estimate of the relative contributions to the emitted gas by both the original enriched source and the native soil N. N-evolution rates measured on arable land under a temperate climate are approximately the same order of magnitude as the N losses estimated by the non-recovery of 15 N method. The third measuring procedure is based on the acetylene inhibition phenomenon. This principle uses the inhibition of bacterial N2O reduction to N2 in the presence of acetylene (C2H2). The methoddetermines the denitrification of all NO3 −-N irrespective of its source. Measurements on classical crop production systems show maximum N losses in the temperate climate of about 20–30 kg N* ha−1 during the growth period of annual crops. A similar level of denitrification is estimated for grassland sites under the same climate. In the subtropics (mediterranean climate with hot summers and mild winters), from both intensively cultivated arable land and grassland sites, N losses may exceed 200 kg* ha−1 year−1. Without the use of irrigation the denitrification flux is negligible in spite of the high temperatures in this climate.
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  • 11
    ISSN: 1432-0789
    Keywords: Denitrification ; Air-filled porosity ; Rhizosphere ; Aerenchyma ; Rice ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Denitrification in the rhizosphere of wheat and rice was studied in relation to aerenchyma formation. Seedlings were grown in quartz silt amended with mineral nutrients at given bulk densities and water tensions. In adventitious wheat roots the formation of cortical lacunae was strongly dependent on soil aeration. Growing the wheat plants in dry (−20 kPa) and moist substrate (−2 kPa) established aerenchyma contents of 3% and 15%, respectively. Denitrification was measured after the introduction of equal moisture levels in the substrates of both treatments. The higher aerenchyma content of roots pregrown in the wetter substrate did not counteract denitrification in the rhizosphere which had doubled in this treatment. In contrast to the unspecific lysis of cortical cell walls, the well organized formation of aerenchyma in rice roots was independent of soil aeration. Root porosity averaged 14%. As in wheat, it was not related to denitrification. However, the level of denitrification per mg of root dry matter was about four times lower than that of wheat. The addition of decomposable organic matter (cellulose) to the substrate stimulated aerenchyma formation in rice and considerably increased denitrification. The results suggest that denitrification in the rhizosphere is independent of aerenchyma formation.
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  • 12
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    Biology and fertility of soils 9 (1990), S. 252-256 
    ISSN: 1432-0789
    Keywords: Nitrapyrin (N-Serve) ; Etridiazole (Dwell) ; 2-Ethynylpyridine ; Urea hydrolysis ; Denitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Laboratory studies to evaluate 3-methylpyrazole-1-carboxamide (MPC) as a soil nitrification inhibitor showed that it was comparable to nitrapyrin (N-Serve) for inhibiting nitrification of ammonium in soil, but was not as effective as etridiazole (Dwell) or 2-ethynylpyridine. They also showed that the effectiveness of MPC as a soil nitrification inhibitor is markedly affected by soil type and soil temperature, that MPC is more effective for inhibiting nitrification of ammonium-N than of urea-N, and that MPC has little, if any, effect on hydrolysis of urea or denitrification of nitrate in soil. These observations and other work discussed indicate that MPC is one of the most promising compounds so far proposed for inhibition of nitrification in soil.
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  • 13
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    Biology and fertility of soils 28 (1999), S. 397-402 
    ISSN: 1432-0789
    Keywords: Key words Surfactants ; Alkylbenzene sulfonate ; Denitrification ; Soil microbial activity ; Wastewater irrigation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  In semi-arid regions wastewater irrigation is a valuable resource for agricultural production. The contamination of irrigated soils with surfactants is one of the ecological risks related to irrigating with untreated wastewater. In this study, the effects of branched alkylbenzene sulfonates (ABS) on microbial biomass, respiratory activity, and denitrification capacity of soil samples (eutric vertisols) taken from an irrigation district in the Mexico City area were investigated in laboratory experiments. Increasing concentrations of ABS lead to a decrease in soil microbial biomass and an increase in soil respiratory activity as well as in the metabolic quotient (qCO2) of the soils. Denitrification capacity was lowest without the addition of ABS and highest at a medium ABS concentration of 50 μg g–1. Denitrification capacity seems to be highly sensitive to ABS addition at moderate concentrations. From the laboratory results, high rates of denitrification and N2O evolution from fields irrigated with wastewater containing ABS are expected.
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  • 14
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    Biology and fertility of soils 22 (1996), S. 326-330 
    ISSN: 1432-0789
    Keywords: Acetate ; Acetylene ; Denitrification ; Ethanoate ; 15N/14N ; Natural abundance ; Nitrification ; Nitrosolobus multiformis ; Nitrosomonas europaea ; 18O/16O ; Oxygen ; Pseudomonas putida ; Succinate ; Waterlogging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The isotopic composition at natural abundance levels of nitrous oxide emitted from a sandy loam, neutral pH soil under a range of soil water contents (matric potentials of-0.1,-1.0 and-5.0 kPa), from soil amended with sodium succinate and sodium ethanoate, and produced by pure cultures of the nitrifying bacteria Nitrosomonas europaea and Nitrosolobus multiformis, and by the denitrifying bacterium Pseudomonas putida, has been determined in laboratory experiments. N2O from all sources was depleted in the 15N and 18O isotopes relative to the conventional references [atmospheric N2 and standard mean ocean water (SMOW), respectively]. N2O from soil was depleted in 15N and 18O to increasing extents with increasing soil water content. The isotopic composition of N2O produced by N. europaea and N. multiformis was similar to that emitted from drier soil (matric potential of-1.0 kPa) and the N2O produced by P. putida was similar to that emitted from wetter soil (matric potential of-0.1 kPa). N2O emitted from the wetter soil was enriched in 15N and 18O compared with that emitted from the drier soil. The differences in isotopic composition between N2O from the wetter and drier soil were attributed principally to isotopic fractionation during N2O reduction to N2 in the terminal step of denitrification. The effect of both sodium succinate and sodium ethanoate amendment was to increase the overall rate of N2O emission, much of which arose from denitrification, as revealed by incubation in 100 kPa O2. In addition, in the sodium ethanoate amended soil N2O reduction to N2 did not occur, as revealed by incubation in 10 kPa C2H2. The N2O from the sodium ethanoate amended soil was depleted in 15N to a greater extent than the sodium succinate amended soil, which is consistent with the observation that N2O reduction to N2 leaves residual N2O relatively enriched in 15N.
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  • 15
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    Biology and fertility of soils 31 (2000), S. 270-278 
    ISSN: 1432-0789
    Keywords: Key words Acetylene inhibition ; Denitrification ; Cotton ; Nitrous oxide entrapment ; 15N-balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  In a 2-year field study, denitrification loss was measured from an irrigated sandy-clay loam under cotton receiving urea-N at 158–173 kg ha–1. An acetylene inhibition-soil core method was employed for the direct measurement of denitrification, considering also the N2O entrapped in the soil. Taking into account the N2O evolved from soil cores and that entrapped in the soil, a total of 65.7 kg N ha–1 and 64.4 kg N ha–1 was lost due to denitrification during the 1995 and 1996 cotton-growing seasons, respectively. Most (〉70%) of the denitrification loss occurred during June–August, a period characterized by high soil temperatures and heavy monsoon rains. On average, 35% of the denitrification-N2O was found entrapped in the soil and the amount of entrapped N2O was significantly correlated with head space N2O concentration and with water-filled pore space. 15N-balance during the 1996 growing season revealed a loss of 71.8 kg N ha–1. It was concluded that a substantial proportion of the fertilizer-N applied to irrigated cotton is lost under the semiarid subtropical climatic conditions prevailing in the Central Punjab region of Pakistan and that denitrification is the major N loss process under irrigated cotton in this region.
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  • 16
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    Biology and fertility of soils 22 (1996), S. 331-335 
    ISSN: 1432-0789
    Keywords: Acetylene ; Denitrification ; Inhibitors ; Nitrification ; Oxygen ; Waterlogging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nitrous oxide emissions from a sandy-loam textured soil wetted to matric potentials of either-1.0 or-0.1 kPa were determined in laboratory experiments in which the soil was incubated in air (control), air plus 10 Pa C2H2 (to inhibit nitrification), 100 kPa O2 (to suppress denitrification), 10 kPa C2H2 (to inhibit N2O reduction to N2 in denitrification) or following autoclaving. The total N2O production, consumption and net N2O emission from the soils together with the contributions to N2O emission from different processes of N2O production were estimated. The rate of N2O production was significantly greater in the wetter soil (282 pmol N2O g-1 soil h-1) than in the drier soil (192 pmol N2O g-1 soil h-1), but because N2O consumption by denitrifiers was also greater in the wetter soil, the net N2O emissions from the wetter and the drier soils did not differ significantly. Non-biological sources made no significant contribution to N2O emission under either moisture regime and biological processes other than denitrification and nitrification made only a small contribution (1% of the total N2O production) in the wetter soil. Denitrifying nitrifiers were the predominant source of N2O emitted from the drier soil and other (non-nitrifying) denitrifiers were the predominant source of N2O emitted from the wetter soil.
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  • 17
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    Biology and fertility of soils 5 (1987), S. 181-187 
    ISSN: 1432-0789
    Keywords: Denitrification ; Rhizosphere ; Bulk density ; Water tension ; Acetylene inhibition method ; Triticum vulgare
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Pot experiments were carried out to study the influence of bulk density (D b), soil water tension (pF) and presence of plants (spring wheat) on denitrification in a low-humus Bt-horizon of a udalf. Pots of only 5-cm depth were found to be most suitable for the experiments when using the acetylene inhibition method. Almost homogeneous soil compaction between 1.1 and 1.6g soil cm−3 was achieved by a Proctor tamper. Water tensions were adjusted by means of ceramic plates on which negative pressure was applied. No denitrification was detected in unplanted pots. With planted pots and increasing bulk density denitrification increased more in pots with 14-day-old plants than in pots with 7-day-old plants. With 14-day-old plants N2O emission pot−1 increased steadily from 2 μmol at D b 1.1 to 8 μmol at D b 1.6, when soil moisture was adjusted to pF 1.5, although root growth was impaired by higher bulk density. From an experiment with different bulk densities and water tensions it could be deduced that the air-filled porosity ultimately determined the rate of denitrification. When low water tension was applied for a longer period, water tension had an overriding effect on total denitrification. Denitrification intensity, however, i.e. the amount of N2O g−1 root fresh weight, was highest when low water tension was accompanied by high bulk density. The results suggest that the increase in denitrification intensity at oxygen stress is partly due to higher root exudation.
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  • 18
    ISSN: 1432-0789
    Keywords: Denitrification ; Cellulose hydrolysis ; Straw ; Cellulolytic-denitrifying bacteria ; N immobilization ; Methane ; Decreasing aerobiosis ; Permanent anaerobiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Laboratory experiments were used to examine the influence of cellulose and straw on denitrification and N immobilization in a sandy loam soil. The soil was mixed with 300 μg nitrate-N/g and incubated in a special vessel under conditions that changed from aerobic to anaerobic or in the permanent absence of O2. Gases (O2, CO2, N2, N2O, NO and CH4) were analysed by gas chromatography at regular intervals and the soil was examined for nitrate, nitrite, ammonium and cellulose. Compared with controls, the application of straw and cellulose (0.5% and 1.0%, respectively) enhanced nitrate immobilization and decreased denitrification, under both anaerobic and originally aerobic (PO2 = 20 vol%) conditions. However, a comparison of results from the aerobic and the anaerobic incubations shows that an increase in denitrification and N immobilization was apparent at an original O2 concentration of 20 vol%. N2 was the major product of denitrification in all experiments. Free methane was apparent as soon as nitrate was respired. The stimulating effect of O2 on total denitrification in the presence of relatively high amounts of easily decomposable cellulose is ascribed to a higher turnover and an intensified mineralization rate (CO2 production), which increased the total demand for electron acceptors.
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    Biology and fertility of soils 32 (2000), S. 385-389 
    ISSN: 1432-0789
    Keywords: Keywords Aeration ; Chloramphenicol ; Denitrification ; Effluent ; Soil water content
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  In land-based wastewater treatment systems (LTS), denitrification is an important nitrogen removal process. We investigated the factors limiting the denitrifying population in a forested LTS, by studying the individual and combined effects of soil aeration, water content, nitrate and carbon on denitrification enzyme activity (DEA). The size of the soil denitrifying population in the LTS appeared to be limited by soil aeration, and limiting oxygen availability increased the denitrifying population above that observed in the field. Furthermore, we found that wastewater irrigation altered the short-term response of denitrifiers to anaerobic soil conditions. Under low oxygen conditions, denitrifiers in the wastewater-irrigated soils produced enzymes sooner and at a greater rate than soils without a history of wastewater irrigation. We propose that the size of the denitrifying population cannot be expected to be large in free-draining, coarsely textured soils even when provided with additional nitrogen and water inputs.
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  • 20
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    Biology and fertility of soils 25 (1997), S. 302-306 
    ISSN: 1432-0789
    Keywords: Key words Anaerobic reoxidation ; Denitrification ; Iron reduction ; Methane ; Successive reduction ; Sulfur oxidation ; Wetland soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Anaerobic reoxidation of reduced products in paddy soils was investigated. Ferrous iron (Fe2+) and monosulfide ion (S2–) added to the soil chemically reduced MnO2 to Mn2+, and MnO2 and Fe(OH)3 to Mn2+ and Fe2+, respectively, where Fe2+ and S2– were considered to be oxidized to Fe3+ and S0. Elemental sulfur was oxidized to sulfate by anaerobic incubation with NO3 – MnO2 and Fe(OH)3. A new conceptual model for the reduction processes in submerged paddy soil including the reoxidation processes of reduced products, in which soil heterogeneity in paddy fields was taken into consideration, was proposed based on the results.
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  • 21
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    Biology and fertility of soils 9 (1990), S. 1-13 
    ISSN: 1432-0789
    Keywords: Denitrification ; Flooded soil ; 15N ; Nitrogen ; Oryza sativa L. ; Wetland rice ; Urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Although denitrification has long been considered a major loss mechanism for N fertilizer applied to lowland rice (Oryza sativa L.) soils, direct field measurements of denitrification losses from puddled rice soils in the tropics have only been made recently. This paper summarizes the results of direct measurement and indirect estimation of denitrification losses from puddled rice fields and reviews the status of research methodology for measurement of denitrification in rice fields. The direct recovery of (N2+N2O)-15N from 15N-enriched urea has recently been measured at sites in the Philippines, Thailand, and Indonesia. In all 12 studies, recoveries of (N2+N2O)-15N ranged from less than 0.1 to 2.2% of the applied N. Total gaseous N losses, estimated by the 15N-balance technique, were much greater, ranging from 10 to 56% of the applied urea-N. Denitrification was limited by the nitrate supply rather than by available C, as indicated by the values for water-soluble soil organic C, floodwater (nitrate+nitrite)-N, and evolved (N2+N2O)-15N from added nitrate. In the absence of runoff and leaching losses, the amount of (N2+N2O)-15N evolved from 15N-labeled nitrate was consistently less than the unrecovered 15N in 15N balances with labeled nitrate, which presumably represented total denitrification losses. This finding indicates that the measured recoveries of (N2+N2O)-15N had underestimated the denitrification losses from urea. Even with a probable two-or threefold underestimation, direct measurements of (N2+N2O)-15N failed to confirm the appreciable denitrification losses often estimated by the indirect difference method. This method, which determines denitrification losses by the difference between total 15N loss and determined ammonia loss, is prone to high variability. Measurements of nitrate disappearance and 15N-balance studies suggest that nitrification-denitrification occurs under alternate soil drying and wetting conditions both during the rice cropping period and between rice crops. Research is needed to determine the magnitude of denitrification losses when soils are flooded and puddled for production of rice.
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  • 22
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    Biology and fertility of soils 26 (1998), S. 224-228 
    ISSN: 1432-0789
    Keywords: Key words CO2 production ; N2O production ; Nitrification ; Denitrification ; NH3 volatilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Carbon (C) and Nitrogen dynamics and sources of nitrous oxide (N2O) production were investigated in a loamy soil amended with pig slurry. Pig slurry (40000kgha–1) or distilled H2O was applied to intact soil cores of the upper 5cm of a loamy soil which were incubated under aerobic conditions for 28 days at 25°C. Treatments were with or without acetylene (C2H2), which is assumed to inhibit the reduction of N2O to dinitrogen (N2), and with or without dicyandiamide (DCD), which is thought to inhibit nitrification. Volatilization of ammonia (NH3), pH, carbon dioxide (CO2) and N2O production, and ammonium (NH4 +) and nitrate NO3 –) concentrations were monitored. The pH of the pig slurry amended soil increased from an initial value of 7.1 to pH 8.3 within 3 days; it then decreased slowly but was still at a value of 7.4 after 28 days. Twenty percent of the NH4 + applied volatilized within 28 days. Sixty percent of the C applied in the pig slurry evolved as CO2, if no priming effect was assumed, but only 38% evolved when the soil was amended with DCD. Pig slurry significantly increased denitrification and the ratio between its gaseous products, N2O and N2, was 0.21. No significant increases in NO3 – concentration occurred, and N2O produced through nitrification was 0.07mg N2O-N kg–1 day–1 or 33% of the total N2O produced. C2H2 was used as a C substrate by microorganisms and increased the production of N2O.
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  • 23
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    Biology and fertility of soils 28 (1998), S. 12-18 
    ISSN: 1432-0789
    Keywords: Key words Subsoil ; Denitrification ; Nitrogen-15 ; Nitrous oxide ; Natural carbon concentrations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Intact, unamended subsoil cores taken from two contrasting field sites were incubated in the laboratory at 12  °C under aerobic (21% O2) and anaerobic (1.1–5.5% O2) conditions. Denitrification of 15N-NO3 – diffusing into the cores across a semi-permeable membrane was estimated by: (1) direct observation of 15N-labelled N2 and N2O, and (2) mass balance following sectioning at the end of the experiment. The in situ denitrification potential (rates where the supply of NO3 – is not limited by diffusion) was estimated using a finite-difference approximation to a diffusion reaction equation based on comparison of time and depth profiles of NO3 – and Br– in the incubated cores. Potentials between 0.2 and 2.5 mg N kg–1 day–1 were obtained under low O2 and natural C concentrations. These results indicate the potential for denitrification in glacial till subsoils to reduce NO3 – leaching to ground or surface waters to levels unlikely to result in a pollution hazard. The major product of NO3 – reduction in these subsoils was observed to be N2, rather than the greenhouse gas and catalyst of stratospheric O3 removal, N2O.
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  • 24
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    Biology and fertility of soils 28 (1998), S. 51-55 
    ISSN: 1432-0789
    Keywords: Key words Nitrous oxide ; Nitrification ; Denitrification ; Soil cores ; Acetylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Nitrous oxide (N2O) emissions via the nitrification (I nit) and denitrification (I den) pathways were successfully measured with in-field incubation of soil cores in preserving jars at 0 Pa and 5–10 Pa acetylene. From the incubations, fractions of nitrification – N2O over total N2O (I nit / I tot) – and denitrification – N2O over total N2O (I den / I tot) – were obtained. Actual field emissions of N2O via nitrification (F nit) and denitrification (F den) were calculated by multiplying the fractions from the incubation technique with the daily N2O emission (F day) determined with a direct soil cover method. The approach presented here was successful for a whole range of soil moisture conditions in intensive grassland. F nit and F den followed the trends of soil ammonium and soil nitrate.
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  • 25
    ISSN: 1432-0789
    Keywords: Denitrification ; Ammonia volatilization ; Wetland rice soils ; Urea ; 15N-balance method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The relative importance of ammonia volatilization and denitrification as loss processes following the application of urea to flooded rice by the traditional method was assessed at four sites with different characteristics in the Philippines. The effect of reducing ammonia loss on denitrification and total N loss was also studied. The total N loss was determined by a 15N-balance method and ammonia volatilization was assessed by a bulk aerodynamic method following the application of urea to small plots (4.8×5.2 m). As run-off was prevented and leaching losses were negligible, the denitrification loss was assessed as the difference between total N loss and ammonia loss. When urea was broadcast into the floodwater at transplanting, the ammonia loss varied from 10% to 56% of the applied N. Loss was smallest at Aguilar where wind speeds were low and the greatest at Mabitac where floodwater pH values and temperatures were high and the winds were strong. The ammonia loss was reduced at all sites by incorporating the urea into the soil by harrowing. However, the reduction achieved varied markedly between sites, with the largest reduction (from 56% to 7% loss of the applied N) being observed at Mabitac. The total N lost from the basal application into the floodwater ranged from 59% to 71% of the applied N. Incorporating the urea by harrowing reduced the total N loss at two sites, increased the total N loss at the third site, and had no effect at the fourth site. The denitrification losses ranged widely (from 3% to 50% of the applied N) when urea was broadcast into the floodwater at the four sites. The denitrification loss was low when the ammonia loss was high (Mabitac) and high when the ammonia loss was low (Aguilar). Reducing ammonia losses by incorporating the urea into the flooded soil resulted in increased denitrification losses at three of the sites and appeared to have no effect on denitrification at the fourth site. The results show that reducing the ammonia loss by incorporating urea into the soil does not necessarily result in reduced total N loss, and suggest that the efficiency of fertilizer N will be improved only when both N-loss processes are controlled simultaneously.
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  • 26
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    Biology and fertility of soils 9 (1990), S. 71-77 
    ISSN: 1432-0789
    Keywords: Denitrification ; Diffusion/reduction model ; Microsites ; Pseudo-equilibrium ; Spatial and temporal variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Denitrification shows both spatial and temporal variability. Any attempt to model the process must take this into account. A model has been developed in which the soil is treated as a large assembly of potentially denitrifying microsites (a modification of the “hot-spot” concept). Chemical and biological heterogeneity is represented by a log-normal distribution of microsite respiration potential. Structural heterogeneity (where present) is accommodated by associating individual microsites with soil aggregates, the radius of which varies log-normally. Spatial variation arises naturally from the existence of microsites. Model microsites are assumed to be in a state of pseudo-equilibrium (a “steady state”). This means that they respond rapidly to any perturbation; it does not imply that they are static. A pseudo-equilibrium model can readily encompass temporal variation provided that the response time of the system is relatively short. Examination of the response times of typical model microsites, by numerical solution of the partial differential equations governing the transient processes occurring within them, suggests that in soils with few large (greater than 10-2m in radius) denitrifying microsites the steady-state approximation is probably adequate. Where denitrification occurs predominantly in large microsites, however, a pseudo-equilibrium model is inappropriate.
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  • 27
    ISSN: 1432-0789
    Keywords: Denitrification ; Flooded soil ; 15N ; Urea ; 15N balance ; Wetland rice ; Oryza sativa L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary It is commonly assumed that a large fraction of fertilizer N applied to a rice (Oryza sativa L.) field is lost from the soil-water-plant system as a result of denitrification. Direct evidence to support this view, however, is limited. The few direct field, denitrification gas measurements that have been made indicate less N loss than that determined by 15N balance after the growing season. One explanation for this discrepancy is that the N2 produced during denitrification in a flooded soil remains trapped in the soil system and does not evolve to the atmosphere until the soil dries or is otherwise disturbed. It seems likely, however, that N2 produced in the soil uses the rice plants as a conduit to the atmosphere, as does methane. Methane evolution from a rice field has been demonstrated to occur almost exclusively through the rice plants themselves. A field study in Cuttack, India, and a greenhouse study in Fort Collins, Colorado, were conducted to determine the influence of rice plants on the transport of N2 and N2O from the soil to the atmosphere. In these studies, plots were fertilized with 75 or 99 atom % 15N-urea and 15N techniques were used to monitor the daily evolution of N2 and N2O. At weekly intervals the amount of N2+N2O trapped in the flooded soil and the total-N and fertilized-N content of the soil and plants were measured in the greenhouse plots. Direct measurement of N2+N2O emission from field and greenhouse plots indicated that the young rice plant facilitates the efflux of N2 and N2O from the soil to the atmosphere. Little N gas was trapped in the rice-planted soils while large quantities were trapped in the unplanted soils. N losses due to denitrification accounted for only up to 10% of the loss of added N in planted soils in the field or greenhouse. The major losses of fertilizer N from both the field and greenhouse soils appear to have been the result of NH3 volatilization.
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  • 28
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    Biology and fertility of soils 7 (1988), S. 1-6 
    ISSN: 1432-0789
    Keywords: Denitrification ; Air-filled porosity ; Rhizosphere effect ; Organic carbon content
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of the air-filled porosity and organic-matter content of the soil on denitrification with non-limiting NO3 − concentrations was studied in unplanted pots and in pots sown to wheat. Four organic-C levels were established by using pure and mixed soil material from a Bt horizon with 0.12% organic-C and an Ap horizon with 1.31% organic C from a mollic luvisol. A range of air-filled porosities from 3% to 25% during denitrification assays was obtained by varying soil compaction. Beyond a 10% to 12% threshold of air-filled porosity the denitrification rates were at an insignificant and constant level in planted as well as in unplanted soil for all organic-C contents. Below this threshold denitrification increased exponentially with decreasing air-filled porosity. In planted soil the excess of denitrification over that of unplanted soil was inversely related to air-filled porosity. This rhizosphere effect on denitrification, which was confined to air-filled porosities lower than 10%–12%, became significantly greater with increasing soil organic-C content. The findings indicate that root dependent respiration amplifies O2 depletion in the rhizosphere and may accelerate the onset of denitrification in planted soil.
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  • 29
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    Biology and fertility of soils 7 (1988), S. 16-22 
    ISSN: 1432-0789
    Keywords: Nitrification activity ; Submerged soils ; Denitrification ; 15N balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrification activity (formation of NO 2 − + NO 3 − per unit soil weight) was measured in the surface layer of 15 presubmerged soils incubated in petri dishes under flooded but aerobic conditions. soils with pH above 5 nitrified quickly, whereas soils with pH below this level did not nitrify or nitrified slowly. The pH values between 7 and 8.5 were optimal for nitrification. Organic-matter levels in the 15 soils of our study did not influence their nitrification activities. In a follow-up greenhouse pot study, after a period of 3 weeks, 15N-balance measurements showed that the loss of N through apparent denitrification did not follow the nitrification patterns of the soils observed in the petri dishes. Apparent denitrification accounted for 16.8% and 18.9% loss of 15N from a soil with insignificant nitrification activity and a soil with high nitrification activity, respectively. These results, thus, indicate a lack of correspondence between the nitrification activities of soil and the denitrification loss of N when the former was measured in the dark and the latter was estimated in the light. Soils that nitrified in the darkness of the incubator did not nitrify in the daylight in the greenhouse.
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    Biology and fertility of soils 7 (1989), S. 336-340 
    ISSN: 1432-0789
    Keywords: Denitrification ; Nitrate ; Methanol ; Ethanol ; Acetone ; Phenylmercuric acetate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Although organic solvents such as methanol and ethanol have been shown to act as energy sources for denitrifying microorganisms, no studies on the influence of organic solvents on denitrification in soil have been reported. Organic solvents have been used as an aid in the application of pesticides and other agricultural chemicals to soil, in studying the effects of these chemicals on denitrification in soil. During these applications, the soil is often aerated or heated to remove the solvent while leaving the chemical in the soil. The work reported here shows that treating soils with methanol, ethanol, or acetone had a very marked effect on their denitrifying ability, even when the soils were aerated thoroughly or heated at 50°C to remove these solvents. This indicates either that it is not possible to effect complete removal of organic solvents from soils by aeration or heating or that organic solvents promote denitrification by solubilizing a fraction of soil organic matter that is not available to denitrifying microorganisms before the addition of these solvents. Experiments using phenylmercuric acetate (a herbicide and nitrification inhibitor) showed that although this compound had a marked inhibitory effect on denitrification when added to soil in methanol, ethanol, or acetone, it had no inhibitory effect on denitrification when added to soil in water. The work reported shows that the use of an organic solvent in adding an agricultural chemical to soil can lead to erroneous conclusions in studies on the effects of the chemical on soil denitrification.
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    Biology and fertility of soils 23 (1996), S. 1-6 
    ISSN: 1432-0789
    Keywords: Key words Nitrification inhibitors ; Cotton ; Denitrification ; Fertilizer recovery ; 2-Ethynylpyridine ; Etridiazole ; Nitrapyrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract N fertilizer is often poorly recovered in irrigated cotton production, due to N loss through denitrification. We researched the ability of inhibitors to delay nitri-fiction and reduce the availability of NO3 – to denitrifying microorganisms and thus improve N fertilizer recovery. 2-Ethynylpyridine, etridiazole, and nitrapyrin proved highly effective nitrification inhibitors, although nitrification was evident several weeks after their application. CaC2 was relatively ineffective, even when wax-coated to prolong the evolution of C2H2. Phenylacetylene and ethynylcyclohexanol were also ineffective, despite having a chemical structure similar to 2-ethynylpyridine. A strong association was identified between each compound‘s ability to inhibit nitrification and its capacity to improve N fertilizer recovery. In one experiment, N fertilizer recovery was increased by ∼50% with 2-ethynylpyridine, etridiazole, or nitrapyrin application, from 33% without inhibitors. The inhibitors had little effect on fertilizer recovery where N losses were relatively small. 3-Methyl pyrazole significantly increased N uptake and lint yield, but the nitrification inhibitors had no significant effect on N uptake or on yield in two of the three of the cotton crops. A laboratory study confirmed that nitrification inhibitor effectiveness declined in the order 2-ethynylpyridine〉etridiazole〉nitrapyrin〉3-methyl pyrazole〉phenylacetylene〉CaC2〉ethynylcyclohexanol
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  • 32
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    Biology and fertility of soils 23 (1996), S. 173-176 
    ISSN: 1432-0789
    Keywords: Denitrification ; Saccharide sources ; Redox conditions ; CO2:N2O ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Cellulose, xylan, and glucose were compared in waterlogged soil as modifying factors of the redox potential (Eh), of the quantity of reducing equivalents, and of the soil capacity to produce N2O and CO2. During the study period (168 h) soils supplied with glucose and xylan showed a higher Eh decrease than the control soil and the soil treated with cellulose. In samples taken after 0, 24, 48, and 168 h, the soils supplied with C showed a higher number of reducing equivalents than the control soil did. These quantities were not correlated with Eh values, nor with N2O production. N2O production was increased compared with the control soil over the entire experimental period in the glucose-amended soils but only after 48 h in the xylan-amended soils and not until 168 h in the cellulose-treated soils. The CO2:N2O ratio was consistently higher than the theoretical value of 2, suggesting that denitrification and CO2 production via fermentation occurred simultaneously. Moreover, this ratio was highly correlated with the Eh values. We conclude that more research is needed to explain the role of soil redox intensity (Eh) and capacity (quantity of redox species undergoing reduction) in the expression of soil denitrification-fermentation pathways.
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    Biology and fertility of soils 23 (1996), S. 229-235 
    ISSN: 1432-0789
    Keywords: Denitrification ; N2-fixation ; Fermentation ; N2O/N2 ratio ; C-availability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nitrate and glucose additions were investigated for their role in the C and N dynamics during anaerobic incubation of soil. A gas-flow soil core method was used, in which the net production of N2, N2O, NO, CO2, and CH4 under a He atmosphere could be monitored both accurately and frequently. In all experiments clayey silt loam soil samples were incubated for 9 days at 25 °C. Addition of nitrate (50 mg KNO3-N kg-1 soil) had no effect on total denitrification and CO2 production rates, while the N2O/N2 ratio was affected considerably. The cumulative N2O production exceeded the cumulative N2 production for 6 days in the treatment with nitrate addition, compared to 1.2 days in the unamended treatment. Glucose addition stimulated the microbial activity considerably. The denitrification rates were limited by the growth rate of the denitrifying population. During denitrification no significant differences were observed between the treatments with 700 mg glucose-C kg-1 and 4200 mg glucose-C kg-1, both in combination with 50 mg KNO3-N kg-1. The N2 production rates were remarkably low, until NO inf3 sup- exhaustion caused rapid reduction of N2O to N2 at day 2. During the denitrification period 15–18 mg N kg-1 was immobilised in the growing biomass. After NO inf3 sup- shortage, a second microbial population, capable of N2-fixation, became increasingly important. This change was clearly reflected in the CO2 production rates. Net volatile fatty acid (VFA) production was monitored during the net N2-fixation period with acetate as the dominant product. N2-fixation faded out, probably due to N2 shortage, followed by increased VFA production. In the high C treatment butyrate became the most important VFA, while in the low C treatment acetate and butyrate were produced at equal rates. During denitrification no VFA accumulation occurred; this does not prove, however, that denitrification and fermentation appeared sequentially. The experiments illustrate clearly the interactions of C-availability, microbial population and nitrate availability as influencing factors on denitrification and fermentation.
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  • 34
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    Biology and fertility of soils 2 (1986), S. 65-70 
    ISSN: 1432-0789
    Keywords: Fertilized soil ; Nitrification ; Denitrification ; N2O production ; C2H2 blockage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A sandy soil amended with different forms and amounts of fertilizer nitrogen (urea, ammonium sulphate and potassium nitrate) was investigated in model experiments for N2O emission, which may be evolved during both oxidation of ammonia to nitrate and anaerobic respiration of nitrate. Since C2H2 inhibits both nitrification and the reduction of N2O to N2 during denitrification, the amount of N2O evolved in the presence and absence of C2H2 represents the nitrogen released through nitrification and denitrification. Results show that amounts of N2O-N lost from soils incubated anaerobically with 0.1% C2H2 and treated with potassium nitrate (23.1 µg N-NO 3 − /g dry soil) exceeded those from soils incubated in the presence of 20% oxygen and treated with even larger amounts of nitrogen as urea and ammonium sulphate. This indicates that nitrogen losses by denitrification may potentially be higher than those occurring through nitrification.
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  • 35
    ISSN: 1432-0789
    Keywords: Key words Ammonia volatilization ; Denitrification ; Dicyandiamide ; Iron pyrites ; Luvisols ; Nitrification ; Urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Laboratory incubation study showed that iron pyrites retarded nitrification of urea-derived ammonium (NH4 +), the effect being greatest at the highest level (10000 mg kg–1 soil). Nitrification inhibition with 10000 mg pyrite kg–1 soil, at the end of 30 days, was 40.3% compared to 55.9% for dicyandiamide (DCD). The inhibitory effect with lower rates of pyrite (100–500 mg kg–1) lasted only up to 9 days. Urea+pyrite treatment was also found to have higher exchangeable NH4 +-N compared to urea alone. DCD-amended soils had the highest NH4 +-N content throughout. Pyrite-treated soils had about 7–86% lower ammonia volatilization losses than urea alone. Total NH3 loss was the most with urea+DCD (7.9% of applied N), about 9% more than with urea alone.
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    Biology and fertility of soils 29 (1999), S. 104-110 
    ISSN: 1432-0789
    Keywords: Key words Nitrification ; Denitrification ; Acetylene ; Soil moisture ; NO production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The NO turnover in soils was measured in two different experimental set-ups, a flow-through system, which is very time-consuming and needs rather sophisticated equipment, and a closed system using serum bottles. We compared the NO turnover parameters (NO consumption rate constant, NO production rate, NO compensation concentration) that were measured with both systems in different soils, under different conditions and in the presence of 10 Pa acetylene to inhibit nitrification. The values of the NO turnover parameters that were measured with the two systems under oxic conditions were usually comparable. The addition of acetylene did not affect the NO consumption rate constants of the soils with the exception of soil G1. However, the NO production rates and the NO compensation concentrations decreased significantly in the presence of acetylene, indicating that nitrification was the main source of NO in these soils. Only one soil (Bol) showed no nitrifying activity. Increasing soil moisture content resulted in decreasing NO consumption rate constants and NO production rates. Even at a high soil moisture content of 80% water holding capacity, nitrification was the main source of NO. The values of the NO turnover parameters that were measured with the two systems were not comparable under anoxic conditions. The NO consumption rate constants and the NO production rates were much lower in the closed than in the flow-through system, indicating that the NO consumption activity became saturated by the high NO concentrations accumulating in the closed system. Under oxic conditions, however, closed serum bottles were a cheap, easy and reliable tool with which to determine NO turnover parameters and to distinguish between nitrification and denitrification as sources of NO.
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  • 37
    ISSN: 1432-0789
    Keywords: Key words Net mineralization ; Nitrification ; Denitrification ; Leaching ; Field incubation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An improved method is described for incubating intact soil cores in the field, which permits concurrent measurement of net mineralization, nitrification, denitrification and leaching. Cores were enclosed in PVC tubes with minimal disturbance to the physical state or to the natural cycles of wetting/drying, soil temperature and aeration during an incubation lasting 4–5 days. An example of the application of the method is given in which soils with contrasting drainage characteristics were compared. Over a 64-day experimental period, 58% of the mineralized nitrogen (N) in a freely drained soil was nitrified and 36% of the nitrate-N (NO3 –-N) was denitrified. In a poorly drained soil, 72% of the mineralized N was nitrified and 63% of the NO3 –-N was denitrified. In both soil types, 18% of the remaining NO3 –-N was leached. Rates of nitrification were significantly correlated with net mineralization (r 2=0.41 and 0.52) and also closely correlated with denitrification (r 2=0.67 and 0.68) in the freely and poorly drained soils, respectively. Independent measurements of these processes, using alternative techniques (for the same period), compared favourably with measurements obtained with the improved incubation method. Adoption of this method has a number of advantages with respect to field net N mineralization, and also allows interpretation of the impact this may have on other N transformation processes.
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  • 38
    ISSN: 1432-0789
    Keywords: Key words Benzoate biodegradation ; Comamonas terrigena ; Denitrification ; Interfacial environment ; Redox potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The purpose of this work was to assess the influence of redox conditions on benzoate biodegradation coupled with oxygen and nitrate as electron acceptors. A benzoate-degrading, facultatively denitrifying bacterium was isolated from a sediment sample and was tentatively identified as Comamonas terrigena (strain J92-6). The experimental system was based on sand columns that were filled with liquid medium containing benzoate and nitrate. The columns were inoculated to provide a fixed biofilm on the sand. Conditions were created by aeration, dinitrogen-purging, and sodium sulfide amendment that comprised oxic, anoxic, and reduced (–375 mV) zones, respectively, at different depths of the columns. Anaerobic biodegradation of benzoate was nitrate-dependent and proceeded at all redox potential values ranging from +400 to –375 mV. Thus, benzoate degradation coupled with denitrification was not inhibited at low redox potentials characteristic of sulfate reduction and methanogenesis. The results demonstrate that the fixed biofilm column system can be successfully used to evaluate the influence of environmental factors on the biodegradation of benzoate, a central decomposition product of anaerobic, aromatic hydrocarbon biodegradation.
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  • 39
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    Biology and fertility of soils 31 (2000), S. 53-59 
    ISSN: 1432-0789
    Keywords: Key words Ammonia volatilization ; Denitrification ; Flooded soils ; Green manure ; Nitrogen-15-labelled¶urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The effects of floodwater algae and green manure on transformations of 15N-urea were studied in columns of a sandy loam soil in a growth chamber. The columns were flooded and either kept in the light, to allow algal growth, or in the dark (control) for 17 days before adding the labelled urea. Changes in urea-, NO3 –- and NH4 +-N levels and the pH of the floodwater were measured over the subsequent 41-day period, during which the control column remained in the dark and those containing algae were maintained either in the dark to cause the death of the algae or in the light. Volatilized NH3 was monitored, and on termination of the experiment the distribution of 15N between NO3 –, NH4 + and organic forms was measured in the soil. Urea hydrolysis was most rapid in the presence of both living algae and green manure, followed by dead algae, and was slowest in the control. The concentration of NH4 +-N in the floodwater was, however, reduced in the presence of algae due to assimilation and NH3 volatilization owing to the raised day-time pH in the floodwater. NH3 volatilization for the first 10 days was rather high in the columns kept in the light compared to those in the dark. Total volatilization plus denitrification losses were greatest where dead algae were present, owing to the absence of live algae which assimilated more than half of the applied N. Algal growth in floodwater increased the depth of the aerobic soil layer present at the soil-water interface. Subsequently, under dark conditions, stimulated algal growth reduced the depth of the aerobic layer causing less nitrification, which resulted in lower losses of N due to denitrification, i.e. 17% of the applied urea-N as compared to 39% in the light treatments. Although the presence of green manure caused a marked increase in the rate of hydrolysis, algal assimilation prevented excessive N losses via volatilization, indicating that the retention of higher quantities of NH4 +-N may have increased fertilizer-N use efficiency.
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  • 40
    ISSN: 1432-0789
    Keywords: Keywords Nitrification ; Denitrification ; Forest soil ; Spatial variation ; Nutrient cycling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  High spatial variation in nitrification potentials has been observed in forest soils, but explanations for this variability have remained speculative. In the present study we determined whether sample treatment, sample size, denitrification or small-scale variations in abiotic properties could explain spatial variation in nitrogen transformations in the organic horizon of a pine forest soil. Net nitrate production in homogenates of the organic horizon was extremely variable. Sample size (60–600 cm2) had no significant effect on nitrate production. In homogenised samples no increased nitrogen production was observed compared to intact incubated cores. High small-scale variation in nitrate production was observed in the litter (L) horizon. When this stratified L layer was subdivided, high net nitrate production was observed in moss (LM) and fragmented needles, whereas no net nitrate production was found in intact needles. The addition of acetylene, inhibiting nitrous oxide reductase, led to significant nitrous oxide production in the L layer. Low nitrous oxide production was found in the LM layer and none in the fragmentation layer. These results show that denitrification can explain part of the spatial variation and plays a major role in nitrogen transformations in the L layer. The relatively higher pH and the presence of fungi are suggested as factors responsible for high denitrification rates in the L layer. As a consequence homogenisation of the organic horizon could lead to highly variable nitrate production due to denitrifying activity from the needles being introduced into other layers.
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  • 41
    ISSN: 1432-0789
    Keywords: Key words N2O release ; Cropping systems ; Waste water treatment ; Activated sludge ; Nitrification ; Denitrification ; Carbon availability ; Available ; carbon-to-nitrate ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nitrous oxide emissions, nitrate, water-soluble carbon and biological O2 demand (BOD5) were quantified in different cropping systems fertilized with varying amounts of nitrogen (clayey loam, October 1991 to May 1992), in an aerated tank (March 1993 to March 1994), and in the nitrification-denitrification unit (March to July 1994) of a municipal waste water treatment plant. In addition, the N2O present in the soil body at different depths was determined (February to July 1994). N2O was emitted by all cropping systems (mean releases 0.13–0.35 mg N2O m–2 h–1), and all the units of the domestic waste water treatment plant (aerated tank 0–6.2 mg N2O m–2 h–1, nitrification tank 0–204,3 mgN2O m–2 h–1, denitrifying unit 0–2.2 mg N2O m–2 h–1). During the N2O-sampling periods estimated amounts of 0.9, 1.5, 2.4 and 1.4 kg N2O-N ha–1, respectively, were released by the cropping systems. The aerated, nitrifying and denitrifying tanks of the municipal waste water treatment plant released mean amounts of 9.1, 71.6 and 1.8 g N2O-N m–2, respectively, during the sampling periods. The N2O emission were significantly positively correlated with nitrate concentrations in the field plots which received no N fertilizer and with the nitrogen content of the aerated sludge tank that received almost exclusively N in the form of NH4 +. Available carbon, in contrast, was significantly negatively correlated with the N2O emitted in the soil fertilized with 80 kg N ha–1 year. The significant negative correlation between the emitted N2O and the carbon to nitrate ratio indicates that the lower the carbon to nitrate ratio the higher the amount of N2O released. Increasing N2O emissions seem to occur at electron donor-to-acceptor ratios (CH2 O or BOD5-to-nitrate ratios) below 50 in the cropping systems and below 1200–1400 in the waste water treatment plant. The trapped N2O in the soil body down to a depth of 90 cm demonstrates that agricultural production systems seem to contain a considerable pool of N2O which may be reduced to N2 on its way to the atmosphere, which may be transported to other environments or which may be released at sometime in the future.
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  • 42
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    Biology and fertility of soils 2 (1986), S. 201-204 
    ISSN: 1432-0789
    Keywords: Fertilizer ; Nitrification ; Denitrification ; N2O emission ; Anhydrous ammonia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Field studies to determine the effect of different rates of fertilization on emission of nitrous oxide (N2O) from soil fertilized with anhydrous ammonia showed that the fertilizer-induced emission of N2O-N in 116 days increased from 1.22 to 4.09 kg ha−1 as the rate of anhydrous ammonia N application was increased from 75 to 450 kg ha−1. When expressed as a percentage of the N applied, the fertilizer-induced emission of N2O-N in 116 days decreased from 1.6% to 0.9% as the rate of fertilizer N application was increased from 75 to 450 kg N ha−1. The data obtained showed that a 100% increase in the rate of application of anhydrous ammonia led to about a 60% increase in the fertilizer-induced emission of N2O. Field studies to determine the effect of depth of fertilizer injection on emission of N2O from soil fertilized with anhydrous ammonia showed that the emission of N2O-N in 156 days induced by injection of 112 kg anhydrous ammonia N ha−1 at a depth of 30 cm was 107% and 21 % greater than those induced by injection of the same amount of N at depths of 10 cm and 20 cm, respectively. The effect of depth of application of anhydrous ammonia on emission of N2O was less when this fertilizer was applied at a rate of 225 kg N ha−1.
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  • 43
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    Biology and fertility of soils 2 (1986), S. 195-199 
    ISSN: 1432-0789
    Keywords: Fertilizer N ; Nitrification ; Denitrification ; N2O emission ; Anhydrous ammonia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Field studies of the effects of different N fertilizers on emission of nitrous oxide (N20) from three Iowa soils showed that the N2O emissions induced by application of 180 kg ha−1 fertilizer N as anhydrous ammonia greatly exceeded those induced by application of the same amount of fertilizer N as aqueous ammonia or urea. On average, the emission of N2O-N induced by anhydrous ammonia was more than 13 times that induced by aqueous ammonia or urea and represented 1.2% of the anhydrous ammonia N applied. Experiments with one soil showed that the N2O emission induced by anhydrous ammonia was more than 17 times that induced by the same amount of N as calcium nitrate. These findings confirm indications from previous work that anhydrous ammonia has a much greater effect on emission of N2O from soils than do other commonly used N fertilizers and merits special attention in research relating to the potential adverse climatic effect of N fertilization of soils. Laboratory studies of the effect of different amounts of NH4OH on emission of N2O from Webster soil showed that the emission of N2O-N induced by addition of 100 μg NH4OH-N g−1 soil represented only 0.18% of the N applied, whereas the emissions induced by additions of 500 and 1 000 μg NH4OH-N g−1 soil represented 1.15% and 1.19%, respectively, of the N applied. This suggests that the exceptionally large emissions of N2O induced by anhydrous ammonia fertilization are due, at least in part, to the fact that the customary method of applying this fertilizer by injection into soil produces highly alkaline soil zones of high ammonium-N concentration that do not occur when urea or aqueous ammonia fertilizers are broadcast and incorporated into soil.
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  • 44
    ISSN: 1432-0789
    Keywords: Key words Acetylene inhibition ; Denitrification ; Farmyard manure ; Irrigated wheat-maize ; Urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Studies were conducted on denitrification in the plough layer of an irrigated sandy-clay loam under a wheat-maize cropping system receiving different fertilizer treatments. The treatments were: N-100 (urea-N at 100kgha–1year–1), N-200 (urea-N at 200kgha–1year–1), FYM-16 (farmyard manure at 16 tonnes ha–1year–1), FYM-32 (farmyard manure at 32 tonnesha–1year–1) and the control (unfertilized). Averaged across sampling dates during the wheat season, the denitrification rate as measured by the C2H2-inhibition/soil-core incubation method was highest in N-200 (83gNha–1day–1), followed by FYM-32 (60gNha–1day–1, N-100 (51gNha–1day–1), FYM-16 (47gNha–1day–1) and the control (33gNha–1 day–1). During the maize growing season, average denitrification rate was highest in FYM-32 (525gNha–1day–1), followed by FYM-16 (408gNha–1day–1), N-200 (372gNha–1day–1, N-100 (262gNha–1day–1) and the control (203gNha–1day–1). Denitrification loss integrated over the whole vegetation period was at a maximum under FYM-32 (13.9kgNha–1), followed by N-200 (11.8kgNha–1), FYM-16 (10.6kgNha–1) and N-100 (8.0kgNha–1), whereas the minimum was observed for the control (5.8kgNha–1). Under both crops, denitrification was significantly correlated with water-filled pore space and soil NO3 –-N. The best multiple regression models accounted for 52% and 70% of the variability in denitrification under wheat and maize, respectively. Results indicated that denitrification is not an important N loss mechanism in this well-drained, irrigated sandy-clay loam under a wheat-maize cropping system receiving fertilizer inputs in the range of 100–200kgNha–1year–1.
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  • 45
    ISSN: 1432-0789
    Keywords: Key words Acetylene inhibition ; Soil core technique ; Denitrification ; Irrigation ; Nitrous oxide entrapment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Two versions of the acetylene inhibition (AI)/soil core method were compared for the measurement of denitrification loss from an irrigated wheat field receiving urea-N at a rate of 100 kg ha–1. With AI/soil core method A, the denitrification rate was measured by analysing the headspace N2O, followed by estimation of N2O dissolved in the solution phase using Bunsen absorption coefficients. With AI/soil core method B, N2O entrapped in the soil was measured in addition to that released from soil cores into the headspace of incubation vessels. In addition, the two methods were also compared for measurement of the soil respiration rate. Of the total N2O produced, 6–77% (average 40%) remained entrapped in the soil, whereas for CO2, the corresponding figures ranged from 12–65% (average 44%). The amount of the entrapped N2O was significantly correlated with the water-filled pore space (WFPS) and with the N2O concentration in the headspace, whereas CO2 entrapment was dependent on the headspace CO2 concentration but not on the WFPS. Due to the entrapment of N2O and CO2 in soil, the denitrification rate on several (18 of the 41) sampling dates, and soil respiration rate on almost all (27 of the 30) sampling dates were significantly higher with method B compared to method A. Averaged across sampling dates, the denitrification rate measured with method B (0.30 kg N ha–1 day–1) was twice the rate measured with method A, whereas the soil respiration rate measured with method B (34.9 kg C ha–1 day–1) was 1.6 times the rate measured with method A. Results of this study suggest that the N2O and CO2 entrapped in soil should also be measured to ensure the recovery of the gaseous products of denitrification by the soil core method.
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  • 46
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    Biology and fertility of soils 32 (2000), S. 321-327 
    ISSN: 1432-0789
    Keywords: Key words Alpine pastures ; Denitrification ; Ion-exchange resins ; Microbial biomass ; Nitrogen cycling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Soil N dynamics were compared in Alpine pastures on two mountains. N-pool sizes and N fluxes were measured relative to N losses via leaching and denitrification in summer. On each mountain, four types of pasture were studied: (1) forest pastures, (2) recently developed pastures formed by forest clearance ("new pastures"), (3) older established pastures, and (4) pastures planted with clover. At both study sites (Scheuchegg and Teufelstein) we obtained similar results. Compared with forest pasture soils, open pasture soils were found to have greater microbial biomass and faster mineralisation potentials, but net field mineralisation rates were slower. In the forest pastures, highest N losses via denitrification were found. Higher potential leaching of NO3 –, estimated by accumulation of NO3 – on ion-exchange resins, in the forest pasture soils suggests lower N uptake by microbes and herbaceous plants compared with open pastures. N2O-production rates of the forest pasture soils at the Scheuchegg site (11.54 μg N2O-N m–2 h–1) were of similar magnitude to those reported for spruce forests without pastures, but at Teufelstein (53.75 μg N2O-N m–2 h–1) they were higher. However, if forest pastures are not overgrazed, no elevated N loss through N2O production and leaching of NO3 – is expected. Denitrification rates in the open pastures (0.83–7.50 μg N2O-N m–2 h–1) were low compared with reports on lowland pastures. In soils of the new pastures, rates of microbial N processes were similar to those in the established pastures, indicating a high capacity of soils to restore their internal N cycle after forest clearance.
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  • 47
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    Biology and fertility of soils 5 (1988), S. 344-349 
    ISSN: 1432-0789
    Keywords: Nitrification ; Deamination ; Grassland ; N fertilisers ; pH ; Denitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Soil nitrification was compared in soils from 89-year-old grassland experimental plots with diverse chemical characteristics. Measurements of NaClO3-inhibited short-term nitrifier activity (SNA) and deamination of 1,2-diamino-4-nitrobenzene were used to study nitrification and deamination activities, respectively, in soil from each of 12 plots. Using multiple regression analysis, an expression for the relationship between SNA, soil pH and fertiliser N additions was derived which indicated that both the frequency and the quantity of farmyard manure additions were important in determining the rate of nitrification. SNA was greatest where there were large and frequent additions of farmyard manure. In soil with pH below 5.2 SNA was very low or insignificant. The effect of (NH4)2SO4 additions could not be assessed because they acidified the soil. We suggest that additions of farmyard manure increase the potential for NO3 − leaching or for denitrification. Deaminase assays indicated that soils with a higher pH showed greater N mineralisation than soils with a lower pH, except at the low extreme. There was no obvious relationship between SNA and deaminase activity at higher levels of pH.
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  • 48
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    Biology and fertility of soils 24 (1997), S. 231-238 
    ISSN: 1432-0789
    Keywords: Key words N2O ; Mechanistic model ; Nitrification ; Denitrification ; Michaelis-Menten kinetics ; Grassland ; Spatial variablity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Seasonal and annual N2O fluxes from urine-affected pasture were approximated with a mechanistic model based on Michaelis-Menten kinetics. The model combined the effects of soil nitrate-N, soil ammonium-N, soil temperature and soil moisture (all from the top 5cm) to calculate N2O emissions from nitrification (F nit ) and denitrification (F den ), with total N2O emission being the sum of the two (F tot =F nit +F den ). Best results were obtained when different kinetic parameters were used for periods of constant soil moisture conditions and after heavy rainfalls when a rapid change of the soil moisture status occurred. Modelled N2O emissions over a year were within the range of uncertainties of measured N2O emissions. Results indicate that the spatial variability of N2O emissions at times when all the model inupt variables were constant may be related to microorganism growth dynamics or enzyme production rates.
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  • 49
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    Biology and fertility of soils 6 (1988), S. 106-111 
    ISSN: 1432-0789
    Keywords: Nitrification ; Denitrification ; Soil water content ; N2O production ; Acetylene ; Ammonium fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of soil water content [60%–100% water-holding capacity (WHC)] on N2O production during autotrophic nitrification and denitrification in a loam soil was studied in a laboratory experiment by selectively inhibiting nitrification with a low C2H2 concentration (2.1 Pa). Nitrifiers usually produced more N2O than denitrifiers. During an initial experimental period of 0–6 days the nitrifiers produced more N2O than the denitrifiers by a factor ranging from 1.4 to 16.5, depending on the water content and length of incubation. The highest N2O production rate by nitrifiers was observed at 90% WHC, when the soil had become partly anaerobic, as indicated by the high denitrification rate. At 100% WHC there were large gaseous losses from denitrification, while nitrification losses were smaller except for the first period of measurement, when there was still some O2 remaining in the soil. The use of 10 kPa C2H2 to inhibit reduction of N2O to N2 stimulated the denitrification process during prolonged incubation over several days; thus the method is unsuitable for long-term studies.
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  • 50
    ISSN: 1432-0789
    Keywords: Denitrification ; Nitrification ; Selective inhibitors ; Nitrapyrin ; Acetylene ; Nitrous oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrapyrin and C2H2 were evaluated as nitrification inhibitors in soil to determine the relative contributions of denitrification and nitrification to total N2O production. In laboratory experiments nitrapyrin, or its solvent xylene, stimulated denitrification directly or indirectly and was therefore considered unsuitable. Low partial pressures of C2H2 (2.5–5.0 Pa) inhibited nitrification and had only a small effect on denitrification, which made it possible to estimate the contribution of denitrification. The contribution of nitrification was estimated by subtracting the denitrification value from total N2O production (samples without C2H2). The critical C2H2 concentrations needed to achieve inhibition of nitrification, without affecting the N2O reductase in denitrifiers, must be individually determined for each set of experimental conditions.
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  • 51
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    Biology and fertility of soils 6 (1988), S. 271-278 
    ISSN: 1432-0789
    Keywords: Denitrification ; Soil moisture ; Roots ; Photosynthesis ; Acetylene inhibition method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Plant effects on the denitrification rate were investigated in pot experiments at different soil moisture tensions and nitrate concentrations. Nitrate concentrations and the soil moisture tension were regulated immediately before each measurement. The effects of the plants on denitrification rates were dependent on the soil moisture tension. At a low soil moisture tension (−7 cm H2O), there was a 10-fold increase in the denitrification rate (planted versus unplanted soil). At a medium moisture tension (−30 cm H2O) the plants had practically no effect, and at the highest tension (−60 cm H2O) the effect was slightly negative. Large differences in denitrification rates under different plant species were observed. At a low soil moisture tension, the average denitrification rate (μg N kg−1 soil h−1) was 39–42 under small grains (barley, wheat, and oats), 47–82 under the grasses (cocksfoot, meadow grass, meadow fescue, and timothy) and 18 under red clover. The differences between the monocots were attributable to differences in plant growth rates, rather than to any specific difference in stimulation or inhibition of denitrification, since the variations in photosynthetic activity fairly well predicted the differences in denitrification rates under different monocots. Clover, however, gave much lower denitrification rates than those predicted by the photosynthetic activity.
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  • 52
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    Pure and applied geophysics 116 (1978), S. 414-422 
    ISSN: 1420-9136
    Keywords: Biogenic sink ; Denitrification ; Nitrous oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Considering only net free energy change for the dissimilatory reduction of nitrate ion, the most efficient reaction with limited organic substrate is that resulting in the production of N2. Under conditions of abundant organic substrate and limited electron acceptor the reduction of nitrate to the level of ammonium would be more efficient. Thus the appearance of N2O in denitrification must reflect a metabolic accident or some reaction barrier (e.g., the activation energy of some intermediate) which prevents the full utilization of this energy. Laboratory studies with microaerophylic systems indicate that under these reducing conditions both nitrate ion and N2O can be reduced to the level of ammonium. The quantitative significance of these processes under natural conditions has not been evaluated but they may provide a significant sink for atmospheric N2O.
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  • 53
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    Environmental geology 24 (1994), S. 1-6 
    ISSN: 1432-0495
    Keywords: Nitrate ; Groundwater ; Modeling ; Denitrification ; Nitrogen balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Implemented on behalf of the Federal Ministry for Research and Technology (BMFT), a model is developed to trace the nutrient flow of nitrate in the soil and the groundwater on a supraregional scale. Research work is intended to indicate regionally differentiated hazardous potentials and thereby provide a basis for recommending comprehensive measures to protect groundwater in Germany. The adaption of the model to the hydrogeological and agricultural conditions of other states is possible in principle. This article focuses on the hydrogeological model parts. A high nitrate pollution of groundwater can be expected in all regions with intensive agricultural use of the topsoil. In particular, groundwater in solid rock areas is susceptible to nitrate pollution. There a rapid groundwater turnover and thus a short residence time for the groundwater in the aquifer is typical. Oxidizing aquifer conditions usually prevail in solid rock aquifers, preventing nitrate degradation. In many loose rock areas, in contrast, the groundwater has a low flow velocity and a long residence time in the aquifer. Because of a lack of free oxygen, a complete degradation of nitrate can occur, as long as iron sulfide compounds and/or organic carbon are available in the aquifer. A more detailed presentation of the whole research work is given in Wendland et al. (1993).
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    Biology and fertility of soils 1 (1985), S. 3-7 
    ISSN: 1432-0789
    Keywords: Nitrification ; Denitrification ; Soil profile
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrous oxide (N2O) fluxes at the soil surface and concentrations at 0.1, 0.2, and 0.3 m were determined in a 40-year-old planted tallgrass (XXX) prairie, a 40-year-old white pine (Pinus strobus) plantation, and field plots treated annually for 18 years either with 33 metric tons of manure ha−1 (330 kg N ha−1) and NH4NO3 (80 kg N ha−1) or with only NH4NO3 (control). Nitrous oxide fluxes from the prairie, forest, manure-amended, and control sites from 13 May to 10 November 1980 ranged from 0.2 to 1.3, 3.5 to 19.5, 3.7 to 79.0, and 1.7 to 24.8 ng N2O-N m−2s−1, respectively. We observed periods when there was no apparent relationship between the N2O flux from the surface and N2O concentrations in the soil profile. This was generally the case in the prairie and in the field sites following the application of N fertilizer. The N2O concentrations in the soil profile increased markedly and coincided with increased soil water content following periods of heavy rainfall for all sites except the prairie. Nitrous oxide concentration gradients indicate that following heavy rainfalls the site of N2O production was moved from the surface deeper into the soil profile. We suggest that the source of N2O production near the surface is nitrification and that N2O is produced by denitrification of NO3 leached into the soil following heavy rainfall.
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    Biology and fertility of soils 1 (1985), S. 189-193 
    ISSN: 1432-0789
    Keywords: Denitrification ; Aerobic respiration ; P02 ; Rendzina soil ; Water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The influence of the partial pressure of oxygen on denitrification and aerobic respiration was investigated at defined P02 values in a mull rendzina soil. The highest denitrification and respiration rates obtained in remoistened, glucose- and nitrate-amended soil were 43 μ1 N20 h−1g−1 soil and 130 μ1 O2 h−1g−1 soil, respectively. At -55 kPa matric water potential, corresponding to 40% water saturation, N20 was produced only below P02 40 hPa. The K m, for O2 was 3.0 x 10−6 M. Formation of N2O and consumption of O2 occurred simultaneously with half maximum rates at P02 6.7–13.3 hPa. Nitrite accumulated in soil below 40 hPa and increased with decreasing pO2. The upper threshold for N20 formation in amended soil was P02 33–40 hPa (39-47 μM O2).
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  • 56
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    Biology and fertility of soils 1 (1985), S. 209-213 
    ISSN: 1432-0789
    Keywords: Denitrification ; Soluble organic carbon ; Electron donors ; Oxygen consumption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The role of soluble organic carbon (SOC) in denitrification in four mineral soils and one organic soil was evaluated in laboratory studies. Denitrification capacities and SOC concentrations were determined by nitrate loss from air-dried flooded soil treated with a solution containing 100 μg/ml N03 −-N, while the rate of consumption was measured by Warburg manometry on 20 g air-dried soils to which 10 ml water had been added. High correlation coefficients (r 〉 0.93) were obtained between denitrification capacities, SOC, and oxygen consumption in the five soils. A mineral soil was amended with extracts of an organic soil. After incubating for 1 week, denitrification capacity was enhanced and SOC concentrations decreased in that soil. Extracted mineral soil had a lower denitrification capacity than an unextracted one. Decreases in concentrations of SOC were related to color change. Infrared spectra of precipitates from soil extracts indicated that absorption at wave number 1420–1440 cm -1 was also related to the color changes. It was implied that low molecular weight fulvic acid like compounds represented the SOC mineralized in denitrification, and that their supply to soil solution by solubilization of organic matter influenced the denitrification rate in the soil.
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  • 57
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    Biology and fertility of soils 10 (1990), S. 139-144 
    ISSN: 1432-0789
    Keywords: Denitrification ; Nitrification ; Chemodenitrification ; Ammonium ; Nitrite ; Nitrate ; Nitric oxide ; Nitrous oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary NO and N2O release rates were measured in an acidic forest soil (pH 4.0) and a slightly alkaline agricultural soil (pH 7.8) after the pH was adjusted to values ranging from pH 4.0 to 7.8. The total release of NO and N2O during 20 h of incubation was determined together with the net changes in the concentrations of NH 4 + , NO 2 − and NO 3 − in the soil. The release of NO and N2O increased after fertilization with NH 4 + and/or NO 3 − ; it strongly decreased with increasing pH in the acidic forest soil; and it increased when the pH of the alkaline agricultural soil was decreased to pH 6.5. However, there was no simple correlation between NO and N2O release or between these compounds and activities such as the NO 2 − accumulation, NO 3 − reduction, or NH 4 + oxidation. We suggest that soil pH exerts complex controls, e.g., on microbial populations or enzyme activities involved in nitrification and denitrification.
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  • 58
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    Biology and fertility of soils 10 (1990), S. 188-193 
    ISSN: 1432-0789
    Keywords: Denitrification ; Dry-sieved ; Wet-sieved ; Aggregates ; Carbon availability ; Water-soluble carbon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The spatial variability of denitrification in soil was studied further by comparing dry-sieved and wetsieved aggregates of different sizes. It was observed that the denitrification rate generally decreased as the drysieved aggregate size increased. In contrast, the denitrification rate increased as the wet-sieved aggregate size increased. In both cases, however, the denitrification rate was positively related to aerobically mineralizable C. Oven-warming of the wet-sieved aggregates at 105°C for 30 min increased the denitrification rate, apparently due to the release of C substrate. Nevertheless, the positive relationship between the denitrification rate and the wetsieved aggregate size persisted. There was no clear relationship between water-soluble C and the denitrification rate. There may have been a contribution from C in microbial polysaccharides in aggregates of different sizes. The results demonstrated that there was a large spatial variability in denitrification over short distances in soil, which was associated with aggregates of different sizes and water stability.
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  • 59
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    Biology and fertility of soils 11 (1991), S. 24-29 
    ISSN: 1432-0789
    Keywords: Denitrification ; Earthworms ; Casts ; Pasture ; Rate determinants ; Acetylene blockage technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Denitrification (using the acetylene block method) was determined in earthworm casts and soils from permanent, drained or undrained pasture plots fertilized with 0 or 200 kg N ha-1 year-1 as ammonium nitrate. Rates of N2O production from soil cores were about three times higher from the fertilized than from the unfertilized plots while drainage had a relatively small effect. Denitrification rates from casts were 3–5 times higher than those from soil irrespective of the drainage treatment. Casts generally had higher NO inf3 sup- , NH inf4 sup+ , and moisture contents, and higher microbial respiration rates than soil. Rates of N2O production were determined primarily by NO inf3 sup- supply, secondarily by moisture; available C did not appear to limit denitrification in these pastures. Estimates of the potential contribution of casts to denitrification ranges from 10.1% of 29.3 kg ha-1 year-1 from the unfertilized, drained plot to 22% of 82.5 kg ha-1 year-1 from the fertilized undrained plot.
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  • 60
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    Biology and fertility of soils 11 (1991), S. 116-120 
    ISSN: 1432-0789
    Keywords: Denitrification ; Flooded soil ; 15N ; Urea ; Wetland rice ; Oryza sativa L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The efficiency of N use in flooded rice is usually low, chiefly due to gaseous losses. Emission of CH4, a gas implicated in global warming, can also be substantial in flooded rice. In a greenhouse study, the nitrification inhibitor encapsulated calcium carbide (a slow-release source of acetylene) was added with 75, 150, and 225 mg of 75 atom % 15N urea-N to flooded pots containing 18-day-old rice (Oryza sativa L.) plants. Urea treatments without calcium carbide were included as controls. After the application of encapsulated calcium carbide, 3.6 μg N2, 12.4 μg N2O-N, and 3.6 mg CH4 were emitted per pot in 30 days. Without calcium carbide, 3.0 mg N2, 22.8 μg N2O-N, and 39.0 mg CH4 per pot were emitted during the same period. The rate of N added had a positive effect on N2 and N2O emissions, but the effect on CH4 emissions varied with time. Carbon dioxide emissions were lower with encapsulated calcium carbide than without. The use of encapsulated calcium carbide appears effective in eliminating N2 losses, and in minimizing emissions of the “greenhouse gases” N2O and CH4 in flooded rice.
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  • 61
    ISSN: 1432-0789
    Keywords: Carbon ; Denitrification ; Immobilisation ; Mineralisation ; Nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A potato crop (Solanum tuberosum L. cv. Maris piper) was grown in a soil to which N was added, as NH4NO3, with or without added C, as sucrose or straw. Shortly after amendment the soil, in all treatments, contained only relatively low levels of mineral N. However, these levels increased later. The increase, which was greatest in the absence of added C and least with added sucrose, occurred before the emergence of the plant canopy. The addition of C to the soil had no effect on plant yield, measured either as dry matter or total N content. The potential nitrification rate was high early in the season, and decreased significantly as the plants developed. The potential denitrification rate showed two significant peaks in activity, possibly related to plant development, the first to the development of new roots and the second to root senescence. It seems probable that the amount of C released by the potato plants was only about one-quarter of that required for the maximum microbial activity.
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  • 62
    ISSN: 1432-0789
    Keywords: Microbial activity ; Gas chromatographic analysis ; Soil atmosphere ; N2O release ; CO2 evolution ; O2 uptake ; Denitrification ; Nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary We have developed a simple method for the determination of gaseous compounds that reflect microbial activity in soil, as affected by factors such as the presence of an organic amendment (peat) or a variation in soil moisture. The method is based on a gas chromatographic analysis of the headspace of vials containing the soil under examination. A single gas chromatograph can detect up to 10 different gases. As expected, after peat was added to the soil, CO2 evolution and O2 uptake increased significantly. Positive relationships were found between the evolution of N2O, and soil moisture and the amount of peat added to the soil. Both the these variables influenced the CO2:O2 ratio. The results given by this method show high reproducibility.
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  • 63
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    Biology and fertility of soils 12 (1991), S. 19-27 
    ISSN: 1432-0789
    Keywords: Manure ; Nitrification ; Denitrification ; Silica gel ; Phospholipids ; Microbial biomass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Following the application of liquid manure to soil, the development of the two processes, nitrification and denitrification, was studied in a two-phase model system. A saturated mixture of manure and soil, stabilized with silica gel, was overlain by an aerobic soil phase. Profiles of the redox potential pH, inorganic N, dissolved organic C, nitrification and denitrification potentials, and phospholipid concentrations for an estimate of microbial biomass were measured during a 20-day period. NH 4 + diffusing into the aerobic soil was oxidized within 10 mm of the interface, but with only a small accumulation of NO 2 - and NO 3 - . It was estimated that N equivalent to approximately 70% of the NH 4 + originally present in the manure was lost through coupled nitrification-denitrification. The potentials for nitrification and denitrification increased 40-and 20-fold, respectively, around the interface. Maximum values were recorded after 14 days. Within 0–5 mm of the anaerobic zone, apparent generation times for NH 4 + -oxidizing bacteria of 1.1–1.8 days were estimated between day 1 and day 7. The phospholipid concentration profiles suggested that the biomass within 2 mm on either side of the interface was stimulated throughout the 20-day period.
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  • 64
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    Biology and fertility of soils 13 (1992), S. 125-129 
    ISSN: 1432-0789
    Keywords: Denitrification ; Carbon substrate ; N2O formation ; Redox conditions ; Electron availability ; Microbial reduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Glucose, acetate, malate, and citrate were added to an agricultural soil. The pe values (-log e-; calculated from the redox potential) obtained 30 min after the addition of C were not correlated with the theoretical reducing power nor with the theoretical total energy of the C compounds. By contrast the number of electron (e-) equivalents was correlated with pe7, indicating that the proton number affected the redox potential (Eh) measurement. After 24 h of incubation, denitrification rates followed the order citrate〉malate〉glucose and control. No N2O production was detected with acetate. Denitrification was not correlated with the theoretical reducing power of the added C compounds but was correlated with pe+pH. Similar numbers of e- equivalents were measured with all treatments. After 72 h of incubation, the order of the denitrification rates was malate〉citrate 〉acetate〉glucose and control. The Eh values (lower than after 24h) did not differ with treatment while the number of e- equivalents was influenced by the quality of the C source. This also demonstrates that the proton number affected the measured Eh. Our results suggest that the different C substrates did not directly influence the soil physicochemical and biological conditions through their degree of oxidation. Any effects appeared to be indirect, arising from the ability of the substrates to generate new metabolites, and consequently initiate different metabolic pathways that modified the soil physicochemical conditions, reducing power and microbial activity.
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    Biology and fertility of soils 13 (1992), S. 200-205 
    ISSN: 1432-0789
    Keywords: Denitrification ; Anaerobically digested sludge ; Desert soil ; Cotton ; Furrow irrigation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary We evaluated potential NO inf3 sup- losses from organic and inorganic N sources applied to improve the growth of cotton (Gossypium hirsutum) on a Pima clay loam soil (Typic Torrifluvent). An initial set of soil cores (April 1989) was collected to a depth of 270 cm from sites in a cotton field previously amended with anaerobically digested sewage sludge or an inorganic N fertilizer. The denitrification potential was estimated in all soil samples by measuring N2O with gas chromatography. Soils amended with a low or high rate of sludge showed increased denitrification activity over soil samples amended with a low rate or inorganic N fertilizer. All amended samples showed greater denitrification activity than control soils. The denitrification decreased with soil depth in all treatments, and was only evident as deep as 90 cm in the soils treated with the high sludge rate. However, when soils collected from depths greater than 90 cm were amended with a C substrate, significant denitrification activity occurred. These date imply that organisms capable of denitrification were present in all soil samples, even those at depths far beneath the root zone. Hence, denitrification was C-substrate limited. A second series of soil cores taken later in the growing season (July 1989) confirmed these data. Denitrification losses (under laboratory conditions) to a soil depth of 270 cm represented 1–4% of total soil N depending on treatment, when the activity was C-substrate limited. With additional C substrate, the denitrification losses increased to 15–22% of the total soil N.
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    Biology and fertility of soils 14 (1992), S. 43-48 
    ISSN: 1432-0789
    Keywords: Denitrification ; Field measurement ; Model simulation ; Soil moisture ; Temperature ; Acetylene inhibition technique ; AIT
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Denitrification activities were measured over a 3-year period in a coarse sandy soil and a sandy loam soil. In all years the crops were spring barley in combination with Italian ryegrass as a catch crop. The denitrification loss was measured using the acetylene inhibition technique on soil cores. Furthermore, a simple model was developed, based on daily values of soil moisture and soil temperature, to calculate the denitrification loss. Soil temperatures for the model were measured, whereas soil moisture was derived from a water-balance model. Measurements of denitrification gave an annual loss of 0.6 kg N ha-1, and the model calculated a loss of 1–2 kg N ha-1 in the coarse sandy soil. In the sandy loam soil annual losses were measured as 1.5, 3.0, and 13.0 kg N ha-1 in 1988, 1989, and 1990, respectively. The corresponding values from the model simulation were 14, 9 and 14 kg N ha-1.
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    Biology and fertility of soils 14 (1992), S. 219-222 
    ISSN: 1432-0789
    Keywords: Denitrification ; Nitrate ; Subsoils ; Organic carbon ; Denitrifying microorganisms ; Plant residues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Previous work in our laboratory indicated that the slow rate of denitrification in Iowa subsoils is not due to a lack of denitrifying microorganisms, but to a lack of organic C that can be utilized by these microorganisms for reduction of NO 3 − . This conclusion was supported by studies showing that drainage water from tile drains under agricultural research plots contained only trace amounts of organic C and had very little, if any, effect on denitrification in subsoils. Aqueous extracts of surface soils promoted denitrification when added to subsoils, and their ability to do so increased with increase in their organic C content. Amendment of surface soils with corn and soybean residues initially led to a marked increase in the amounts of organic C in aqueous extracts of these soils and in the ability of these extracts to promote denitrification in subsoils, but these effects were short-lived and could not be detected after incubation of residue-treated soils for a few days. We conclude from these observations that water-soluble organic C derived from plant residues is decomposed so rapidly in surface soils that very little of this C is leached into subsoils, and that this largely accounts for the slow rate of denitrification of nitrate in subsoils.
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  • 68
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    Biology and fertility of soils 15 (1993), S. 21-27 
    ISSN: 1432-0789
    Keywords: NO production ; NO consumption ; Chemodenitrification ; Nitrification ; Denitrification ; Activation energy ; Temperature optimum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The temperature dependence of the NO production rate and the NO consumption rate constant was measured in an Egyptian soil, a soil from the Bavarian Forest, and a soil from the Donau valley, together with the temperature dependence of the potential rates of ammonium oxidation, nitrite oxidation, and denitrification, and the temperature dependence of the growth of NH inf4 sup+ -oxidizing, NO inf2 sup- -oxidizing, and NO inf3 sup- -reducing bacteria in most probable number assays. In the acidic Bavarian Forest soil, NO production was only stimulated by the addition of NO inf3 sup- but not NH inf4 sup+ . However, NO production showed no temperature optimum, indicating that it was due to chemical processes. Most probable numbers and potential activities of nitrifiers were very low. NO consumption, in contrast, showed a temperature optimum at 25°C, demonstrating that consumption and production of NO were regulated individually by the soil temperature. In the neutral, subtropical Egyptian soil, NO production was stimulated only by the addition of NH inf4 sup+ but not NO inf3 sup- . All activities and most probable numbers showed a temperature optimum at 25° or 30°C and exhibited apparent activation energies between 61 and 202 kJ mol-1. However, a few nitrifiers and denitrifiers were also able to grow at 8° or 50°C. Similar temperature characteristics were observed in the Donau valley soil, although it originated from a temperate region. In this soil NO production was stimulated by the addition of NH inf4 sup+ or of NO inf3 sup- . Both NO production and consumption were stimulated by drying and rewetting.
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  • 69
    ISSN: 1432-0789
    Keywords: Acetylene inhibition technique ; Denitrification ; Carbon: nitrate ratio ; Acetylene blockage ; Reliability of AIT ; N2O-reductase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In model experiments with a silty loam soil the effect of different C : NO inf3 sup- -N ratios on the reliability of C2H2 (1% v/v) in blocking N2O-reductase activity was examined. The soil was carefully mixed with different amounts of powdered lime leaves (Tilia vulgaris) to obtain organic C contents of about 1.8, 2.3, and 2.8%, and of NO inf3 sup- solution to give C : NO inf3 sup- -N ratios of 84, 107, 130, 156, 200, and 243. The soil samples were incubated in specially modified anaerobic jars (22 days, 25°C, 80% water-holding capacity, He atmosphere) and the atmosphere was analysed for N2, N2O, CO2, and C2H2 by gas chromatography at regular intervals. Destruction jars were used to analyse soil NO inf3 sup- , NH 4 + and C. The results clearly showed that N2O-reductase activity was completely blocked by 1% (v/v) C2H2 only as long as NO inf3 sup- was present. In the presence of C2H2, NO inf3 sup- was apparently entirely converted into N2O. The C2H2 blockage of N2O-reductase activity ceased earlier in soils with a wide C : NO inf3 sup- -N ratio (156, 200, and 243) than in those with closer C : NO inf3 sup- -N ratios (84, 107, and 130). As soon as NO inf3 sup- was exhausted, N2O was reduced to N2 in spite of C2H2. The wider the C : NO inf3 sup- -N ratio, the earlier the production of N2 and the less the reliability of the C2H2 blockage. In the untreated control complete inhibition of N2O-reductase activity by C2H2 lasted for 7–12 days. In the field, estimates of total denitrification losses by the C2H2 inhibition technique should be considered reliable only as long as NO inf3 sup- is present. Consequently, NO inf3 sup- monitoring in the field is essential, particularly in soils supplied with easily decomposable organic matter.
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  • 70
    ISSN: 1432-0789
    Keywords: Denitrification ; Soil moisture ; Remote sensing ; Infrared emission ; N fluxes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Remote sensing techniques may be one way to narrow the range of uncertainty in extrapolating N2 emissions from small-scale to large-scale terrestrial ecosystems. In the present work we investigated the correlations between denitrification activity, soil moisture, and soil thermal infrared emissions. A field experiment was performed on two different agricultural soils, one loam and one silty clay. The results indicated that thermal infrared emissions can only be used to estimate the denitrification rate in soil within a limited range of soil moisture levels. Estimates of denitrification activity based on soil texture and moisture are, however, very likely to be a fruitful approach to generating large-scale N fluxes.
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    Biology and fertility of soils 21 (1996), S. 77-83 
    ISSN: 1432-0789
    Keywords: Denitrification ; Field experiment ; Acetylene inhibition technique ; Nitrate ; Soil moisture ; Vicia faba ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Denitrification rates were studied using the C2H2 inhibition technique in a 2-year field experiment within plots of nodulated and non-nodulated faba beans, ryegrass, and cabbage. Denitrification rates ranged from 14.40 to 0.02 ng N2O−N g−1 soil dry weight h−1. Mean denitrification increased fourfold in plots of N2−fixing Vicia faba compared to non-nodulated V. faba mutant F48, Lolium perenne, and Brassica oleracea. The results with and without C2H2 treatment indicate that in the field the major part of this enhanced denitrification led to the endproduct N2 rather than to the ozone-degrading N2O. Higher denitrification rates of plots with N2−fixing plants in September seemed to be caused by an increase in soil NO inf3 sup- of about 20 kg ha−1 found between July and August. Soil NO inf3 sup- and soil moisture explained 67% of the variation in denitrification rates of the different soil samples over the growing seasons in the 2 years. Soil moisture explained 44% of the variation for soil planted with N2−fixing plants and 62% for soil planted with non-fixing plants. Positive exponential relationships were obtained between denitrification rates and soil nitrate (r=0.71) and soil moisture (r=0.82).
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  • 72
    ISSN: 1432-0789
    Keywords: Microbial biomass ; Denitrification ; Nitrification ; Nitrate ; Organic C
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A field study was undertaken to determine the effects of different plant species on soil microbial biomass and N transformations in a well drained silty clay loam (Typic Dystrochrept) and a poorly drained clay loam (Typic Humaquept). The crop treatments were faba bean (Vicia faba L.), alfalfa (Medicago sativa L.), timothy (Phleum pratense L.), bromegrass (Bromus inermis L.), reed canarygrass (Phalaris arundinacea L.), and wheat (Triticum aestivum L.). Measurements of microbial biomass C, denitrification capacity, and nitrification capacity were performed periodically in the top 2–10 cm of soil. On most sampling dates, all three parameters were higher under perennial than under annual species. The nitrification capacity was positively affected by the level of N applied to each species (r=0.65** for the silty clay loam and 0.84*** for the clay loam) and not directly by the plant. The differences found in microbial biomass C were significantly correlated with the water-soluble organic C present under each plant species (r=0.74*** for the silty clay loam and 0.90*** for the clay loam), suggesting differences in C deposition in the soil among plant species. In the silty clay loam, the denitrification capacity was positively related to the amount of organic C found under each plant species, while in the clay loam, it was dependent on the amount of N applied to each species. There was less denitrification activity per unit biomass under legume species than under graminease, suggesting that, depending on their composition, root-derived materials may be used differently by soil microbes.
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  • 73
    ISSN: 1432-0789
    Keywords: Key words Microbial biomass ; Denitrification ; Nitrification ; Nitrate ; Organic C
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A field study was undertaken to determine the effects of different plant species on soil microbial biomass and N transformations in a well drained silty clay loam (Typic Dystrochrept) and a poorly drained clay loam (Typic Humaquept). The crop treatments were faba bean (Vicia faba L.), alfalfa (Medicago sativa L.), timothy (Phleum pratense L.), bromegrass (Bromus inermis L.), reed canarygrass (Phalaris arundinacea L.), and wheat (Triticum aestivum L.). Measurements of microbial biomass C, denitrification capacity, and nitrification capacity were performed periodically in the top 2–10 cm of soil. On most sampling dates, all three parameters were higher under perennial than under annual species. The nitrification capacity was positively affected by the level of N applied to each species (r=0.65** for the silty clay loam and 0.84*** for the clay loam) and not directly by the plant. The differences found in microbial biomass C were significantly correlated with the water-soluble organic C present under each plant species (r=0.74*** for the silty clay loam and 0.90*** for the clay loam), suggesting differences in C deposition in the soil among plant species. In the silty clay loam, the denitrification capacity was positively related to the amount of organic C found under each plant species, while in the clay loam, it was dependent on the amount of N applied to each species. There was less denitrification activity per unit biomass under legume species than under gramineae, suggesting that, depending on their composition, root-derived materials may be used differently by soil microbes.
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  • 74
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    Biology and fertility of soils 22 (1996), S. 326-330 
    ISSN: 1432-0789
    Keywords: Key words Acetate ; Acetylene ; Denitrification ; Ethanoate ; 15N/14N ; Natural abundance ; Nitrification ; Nitrosolobus multiformis ; Nitrosomonas europaea ; 18O/16O ; Oxygen ; Pseudomonas putida ; Succinate ; Waterlogging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The isotopic composition at natural abundance levels of nitrous oxide emitted from a sandy loam, neutral pH soil under a range of soil water contents (matric potentials of –0.1, –1.0 and –5.0 kPa), from soil amended with sodium succinate and sodium ethanoate, and produced by pure cultures of the nitrifying bacteria Nitrosomonas europaea and Nitrosolobus multiformis, and by the denitrifying bacterium Pseudomonas putida, has been determined in laboratory experiments. N2O from all sources was depleted in the 15N and 18O isotopes relative to the conventional references [atmospheric N2 and standard mean ocean water (SMOW), respectively]. N2O from soil was depleted in 15N and 18O to increasing extents with increasing soil water content. The isotopic composition of N2O produced by N. europaea and N. multiformis was similar to that emitted from drier soil (matric potential of –1.0 kPa) and the N2O produced by P. putida was similar to that emitted from wetter soil (matric potential of –0.1 kPa). N2O emitted from the wetter soil was enriched in 15N and 18O compared with that emitted from the drier soil. The differences in isotopic composition between N2O from the wetter and drier soil were attributed principally to isotopic fractionation during N2O reduction to N2 in the terminal step of denitrification. The effect of both sodium succinate and sodium ethanoate amendment was to increase the overall rate of N2O emission, much of which arose from denitrification, as revealed by incubation in 100 kPa O2. In addition, in the sodium ethanoate amended soil N2O reduction to N2 did not occur, as revealed by incubation in 10 kPa C2H2. The N2O from the sodium ethanoate amended soil was depleted in 15N to a greater extent than the sodium succinate amended soil, which is consistent with the observation that N2O reduction to N2 leaves residual N2O relatively enriched in 15N.
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  • 75
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    Biology and fertility of soils 22 (1996), S. 331-335 
    ISSN: 1432-0789
    Keywords: Key words Acetylene ; Denitrification ; Inhibitors ; Nitrification ; Oxygen ; Waterlogging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nitrous oxide emissions from a sandy-loam textured soil wetted to matric potentials of either –1.0 or –0.1 kPa were determined in laboratory experiments in which the soil was incubated in air (control), air plus 10 Pa C2H2 (to inhibit nitrification), 100 kPa O2 (to suppress denitrification), 10 kPa C2H2 (to inhibit N2O reduction to N2 in denitrification) or following autoclaving. The total N2O production, consumption and net N2O emission from the soils together with the contributions to N2O emission from different processes of N2O production were estimated. The rate of N2O production was significantly greater in the wetter soil (282 pmol N2O g–1 soil h–1) than in the drier soil (192 pmol N2O g–1 soil h–1), but because N2O consumption by denitrifiers was also greater in the wetter soil, the net N2O emissions from the wetter and the drier soils did not differ significantly. Non-biological sources made no significant contribution to N2O emission under either moisture regime and biological processes other than denitrification and nitrification made only a small contribution (1% of the total N2O production) in the wetter soil. Denitrifying nitrifiers were the predominant source of N2O emitted from the drier soil and other (non-nitrifying) denitrifiers were the predominant source of N2O emitted from the wetter soil.
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  • 76
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    Biology and fertility of soils 18 (1994), S. 1-6 
    ISSN: 1432-0789
    Keywords: Ammonium ; Denitrification ; Nitrification ; Nitrous oxide ; Organic carbon ; Acetylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We observed that soil cores collected in the field containing relatively high NH inf4 sup+ and C substrate levels produced relatively large quantities of N2O. A series of laboratory experiments confirmed that the addition of NH inf4 sup+ and glucose to soil increase N2O production under aerobic conditions. Denitrifying enzyme activity was also increased by the addition of NH inf4 sup+ and glucose. Furthermore, NH inf4 sup+ and glocose additions increased the production of N2O in the presence of C2H2. Therefore, we concluded that denitrification was the most likely source of N2O production. Denitrification was not, however, directly affected by NH inf4 sup+ in anaerobic soil slurries, although the use of C substrate increased. In the presence of a high substrate C concentration, N2O production by denitrifiers may be affected by NO inf3 sup- supplied from NH inf4 sup+ through nitrification. Alternatively, N2O may be produced during mixotrophic and heterotrophic growth of nitrifiers. The results indicated that the NH inf4 sup+ concentration, in addition to NO inf3 sup- , C substrate, and O2 concentrations, is important for predicting N2O production and denitrification under field conditions.
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  • 77
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    Biology and fertility of soils 23 (1996), S. 1-6 
    ISSN: 1432-0789
    Keywords: Nitrification inhibitors ; Cotton ; Denitrification ; Fertilizer recovery ; 2-Ethynylpyridine ; Etridiazole ; Nitrapyrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract N fertilizer is often poorly recovered in irrigated cotton production, due to N loss through denitrification. We researched the ability of inhibitors to delay nitrition and reduce the availability of NO3 - to denitrifying microorganisms and thus improve N fertilizer recovery, 2-Ethynylpyridine, etridiazole, and nitrapyrin proved highly effective nitrification inhibitors, although nitrification was evident several weeks after their application. CaC2 was relatively ineffective, even when wax-coated to prolong the evolution of C2H2. Phenylacetylene and ethynylcyclohexanol were also ineffective, despite having a chemical structure similar to 2-ethynylpyridine. A strong association was identified between each compound's ability to inhibit nitrification and its capacity to improve N fertilizer recovery. In one experiment, N fertilizer recovery was increased by ∼50% with 2-ethynylpyridine, etridiazole, or nitrapyrin application, from 33% without inhibitors. The inhibitors had little effect on fertilizer recovery where N losses were relatively small. 3-Methyl pyrazole significantly increased N uptake and lint yield, but the nitrification inhibitors had no significant effect on N uptake or on yield in two of the three of the cotton crops. A laboratory study confirmed that nitrification inhibitor effectiveness declined in the order 2-ethynylpyridine〉etridiazole〉nitrapyrin〉3-methyl pyrazole〉phenylacetylene〉CaC2〉ethynylcyclohexanol
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  • 78
    ISSN: 1432-0789
    Keywords: Heavy metals ; Microbial biomass ; Respiration ; Enzymes ; Denitrification ; Dimethyl sulphoxide reduction ; Nematodes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Microbial properties and nematode abundance were measured along a gradient of increasing Cu, Cr, and As concentrations (50–1300 mg Cr kg-1) in the top 5 cm of a pasture soil contaminated by runoff of preserving liquor from an adjacent timber-treatment plant. Microbial biomass C and N were significantly (P〈0.05) lower in contaminated than uncontaminated soils. The amount of microbial biomass C as a percentage of total organic C declined significantly (r 2 value with Cr 0.726*) with increasing contamination, and the ratio of respired C to biomass C was significantly (P〈0.05) higher with contamination. Substrate-induced respiration, microbial biomass P, and denitrification declined (r2 value with Cr 0.601, 0.833*, and 0.709*, respectively) with increasing contamination. Increasing contamination had no effect on prokaryote substrate-induced respiration but eukaryote: eukaryote substrate-induced respiration declined significantly (r 2 value with Cr 0.722*). Accordingly, the ratio of prokaryote substrate-induced respiration increased significantly (r 2 value with Cr 0.799*) with contamination. There was a significant (r 2 value with Cr 0.872*) hyperbolic relationship between sulphatase activity and contamination, with activity declining by approximately 80% at 〉1000 mg Cr kg-1. Increasing contamination had no effect on basal respiration, dimethyl sulphoxide reduction, and phosphatase, urease, and invertase activities. Numbers of plant-associated nematodes declined significantly (r 2 value with Cr 0.780*) with contamination. On a percentage basis, plant-feeding nematodes predominated in less contaminated soils, whereas bacterial-feeding and predatory nematodes predominated in heavily contaminated soils. The use of the fumigation—incubation procedure for measurement of microbial biomass C in heavy-metal contaminated soils is discussed.
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  • 79
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    Biology and fertility of soils 15 (1993), S. 132-136 
    ISSN: 1432-0789
    Keywords: Denitrification ; Nitrate ; Subsoils ; Organic carbon ; Denitrifying microorganisms ; Freezing ; Drying ; Plants ; Plant residues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Recent work in our laboratory indicated that the slow rate of denitrification in Iowa subsoils is not due to a lack of denitrifying microorganisms, but to a lack of organic C that can be utilized by these microorganisms for reduction of nitrate. To identify factors affecting the availability of leachable organic C in surface soils capable of promoting denitrification in subsoils, we studied the effects of freezing and drying and of plants and plant residues on the amounts of water-soluble organic C in surface soils and the ability of this organic C to promote denitrification in subsoils. We found that aqueous extracts of field-moist, frozen, and air-dried surface soils promoted denitrification in subsoils and that their stimulatory effects on denitrification were highly correlated (r=0.93) with their organic C contents and decreased in the order air-dried soils ≫ frozen soils 〉field-moist soils. But a detailed study of the effect of drying a surface soil to different water tensions indicated that drying of soils under natural conditions is not likely to lead to a substantial increase in their content of water-soluble organic C. Amendment of surface soils with corn or soybean residues led to a marked increase in the amount of organic C in aqueous extracts of the soils and in the ability of these extracts to promote denitrification in subsoils. These effects of plant residues could not be detected after incubation of residue-treated soils for a few days under aerobic conditions, but they increased markedly with an increase in the time of incubation from 1 to 10 days when residue-treated soils were incubated under anaerobic conditions. Analyses for organic acids indicated that this increase was largely due to fermentative production of acetic, propionic, and butyric acids by soil microorganisms. Growth chamber studies showed that growth of corn, soybean, wheat, and sorghum plants on surface soil did not significantly increase the organic C content of leachates of the soil or the ability of these leachates to promote denitrification in subsois. We conclude that plant residues are a major source of the leachable organic C in surface soils that is capable of promoting denitrification in subsoils.
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  • 80
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    Biology and fertility of soils 15 (1993), S. 196-200 
    ISSN: 1432-0789
    Keywords: Bradyrhizobium japonicum ; Denitrification ; Paddy-upland rotation ; Indigenous populations ; Soybean ; Alcaligenes denitrificans ; N2O production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In Japan some paddy fields are used for upland crops for several years and then returned to paddy fields (paddy-upland rotation). Soybeans (Glycine max L.) are an important summer crop. The ability to denitrify and some characteristics of denitrification by isolated strains of Bradyrhizobium japonicum were investigated to clarify the frequency of denitrifiers in indigenous populations of B. japonicum in fileds under paddyupland rotation. Eight field plots with different cropping systems at two sites were used. The fields consisted of a Gray Lowland Soil, and either soybeans or paddy rice (Oryza sativa L.) was grown as a summer crop, with barley (Hordeum distichum L.) or wheat (Triticum aestivum L.) as a winter crop. All B. japonicum strains present in the plots were able to denitrify. Isolated strains fell into two main groups (groups I and II) according to the rate of denitrification. Strains of group I evolved N2O with C2H2 at a rate comparable to that of Alcaligenes denitrificans IAM 12370, whereas the denitrification activity of group II strains was 100 times lower than that of group I strains. Both group I and II strains occurred in each plot. Amounts of N2O produced by indigenous strains with and without C2H2 suggested that strains of group I and II evolved N2 or N2O, respectively, as the end product of denitrification. One strain (S 107) that was isolated had the highest denitrifying ability with an end product of N2O. These results indicate that indigenous bradyrhizobia may partly contribute to denitrification of field soil under a paddy-upland rotation.
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  • 81
    ISSN: 1432-0789
    Keywords: Nitrification ; Denitrification ; Nitrification inhibitors ; 15N balance ; Nitrous oxide ; Greenhouse gases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effectiveness of wax-coated calcium carbide (as a slow-release source of acetylene) and nitrapyrin in inhibiting nitrification and emission of the greenhouse gases N2O and CH4 was evaluated in a microplot study with dry-seeded flooded rice grown on a grey clay near Griffith, NSW, Australia. The treatments consisted of factorial combinations of N levels with nitrification inhibitors (control, wax-coated calcium carbide, and nitrapyrin). The rate of nitrification was slowed considerably by the addition of wax-coated calcium carbide, but it was inhibited only slightly by the addition of nitrapyrin. As a result, the emission of N2O was markedly reduced by the application of wax-coated calcium carbide, whereas there was no significant difference in rates of N2O emission between the control and nitrapyrin treatments. Both nitrification inhibitors significantly reduced CH4 emission, but the lowest emission rates were observed in the wax-coated calcium carbide treatment. At the end of the experiment 84% of the applied N was recovered from the wax-coated calcium carbide treatment compared with ∼ 43% for the nitrapyrin and control treatments.
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  • 82
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    Biology and fertility of soils 16 (1993), S. 157-162 
    ISSN: 1432-0789
    Keywords: Denitrification ; Soil respiration ; Nitrous oxide ; Tropical volcanic soils ; Microbial biomass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Effects of vegetation and nutrient availability on potentail denitrification rates were studied in two volcanic, alluvial-terrace soils in lowland Costa Rica that differ greatly in weathering stage and thus in availability of P and base cations. Potential denitrification rates were significantly higher in plots where vegetation had been left undisturbed than in plots where all vegetation had been removed continuously, and were higher on the less fertile of the two soils. The potential denitrification rates were correlated strongly with respiration rates, levels of mineralizable N, microbial biomass, and moisture content, and moderately well with concentrations of extractable NH inf4 sup+ , Kjeldahl N, and total C. In all plots, denitrification rates were stimulated by the removal of O2 and by the addition of glucose but not by the addition of water or NO inf3 sup- .
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  • 83
    ISSN: 1432-0789
    Keywords: Denitrification ; Nitrogen immobilization ; Water-sediment system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of wheat straw and different forms of N on denitrification and N immobilization were studied in an anaerobic water-sediment system. The water-sediment system was supplemented with various combinations of wheat straw and 15N-labelled and unlabelled (NH4)2SO4 or KNO3, and incubated anaerobically at 30°C for 10 days. 15N-labelled and unlabelled NO inf3 sup- , NO inf2 sup- , NH inf4 sup+ , and organic N were determined in the water-sediment system. The gases evolved (N2, CO2, N2O, and CH4) were analyzed by gas chromatography at regular intervals. Larger quantities of 15N2−N and organic 15N were formed in wheat straw-amended systems than in non-amended systems. Trends in CO2 production were similar to those of N2−N evolution. The evolution of N2O and CH4 was negligible. Denitrification processes accounted for about 22 and 71% of the added 15NO inf3 sup- −N in the absence and presence of wheat straw, respectively. The corresponding denitrification rates were 3.4 and 12.4 μg 15Ng-1 dry sediment day-1. In systems amended with 15NO inf3 sup- −N and 15NO inf3 sup- +NH inf4 sup+ −N without wheat straw, 1.82 and 1.58%, respectively, of the added 15NH inf3 sup- −N was immobilized. The corresponding figures for the same systems supplemented with wheat straw were 5.08 and 4.10%, respectively. Immobilization of 15NO inf4 sup+ −N was higher than that of 15NO inf3 sup- −N. The presence of NO inf3 sup- −N did not stimulate NH inf4 sup+ −N immobilization.
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  • 84
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    Biology and fertility of soils 18 (1994), S. 42-48 
    ISSN: 1432-0789
    Keywords: N2O ; Coated Calcium Carbide ; Acetylene ; Nitrification ; Denitrification ; Soil respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Coated CaC2 is a newly developed product which can supply nitrification-inhibiting quantities of C2H2 (1–10 Pa) to the soil, throughout a cropping season. This method of applying C2H2 to the soil maintains C2H2 in the soil continuously for several months. It is not know whether these low C2H2 concentrations alter soil microbial processes. A field study was initiated to determine the effect of supplying C2H2 to a clay soil, using coated CaC2, on soil respiration, denitrification, nitrification, and C2H2 consumption. The C2H2 consumption rate increased with length of soil exposure to C2H2 (r 2=0.59). The rates of CO2 production (r 2=0.88) and denitrification (r 2=0.86) were both highly correlated with the C2H2 consumption rates. The nitrifier potential decreased to a minimum of 21% of the control after 3 months of C2H2 treatment. After this time, nitrifier activity increased to 41% of the control after 11 months of treatment. This increase was due to increased C2H2 consumption in the soil. After 3 months of continuous application of C2H2 to the soil, the C2H2 concentrations were generally below that necessary to inhibit nitrification. No adaptation to the C2H2 by nitrifiers was found. Repeating these measurements 1 year later showed that soils previously exposed to C2H2 retained their enhanced C2H2 oxidation capacity and the capacity to use C2H2 to increase denitrification. Nitrification potentials remained about 50% lower in soils exposed to C2H2 a year earlier compared to soils not previously exposed to C2H2.
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  • 85
    ISSN: 1432-0789
    Keywords: Denitrification ; Ammonia volatilization ; Phosphoroamides ; Urea hydrolysis ; Acetylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We studied the interacting effects on NH3 loss and grain yield of adding (1) urease inhibitors to retard the hydrolysis of urea (2) the algicide terbutryn to limit floodwater pH increases, and (3) C2H2 (provided by waxcoated calcium carbide) to prevent NH3 oxidation. The algicide treatment maintained the floodwater pH values below 8 for the first 3 days after the urea application and depressed the maximum values below 8.5 on subsequent days. As a consequence, NH3 loss was significantly (P〈0.05) reduced in all treatments containing algicide. The addition of wax-coated calcium carbide effectively inhibited nitrification, as judged by the increased ammoniacal (NH3+NH4) N concentrations in the floodwater, However, these increased ammonical-N concentrations resulted in large losses of NH3. The results also showed that the effectiveness of a urease inhibitor cannot be judged solely from the ammonical-N concentrations in the floodwater of a single treatment with the inhibitor. Additional treatments with an algicide and a nitrification inhibitor are required to determine whether the low ammoniacal-N concentrations are caused by NH3 losses and nitrification. Thus N-(n-butyl)thiophosphorictriamide (NBPT) appeared to retard urea hydrolysis when judged by the low ammoniacal-N concentrations in the floodwater; however, treatments with NBPT, algicide, and C2H2 showed that the low concentrations were mainly a result of NH3 volatilization and nitrification. Even though NBPT did not completely inhibit urea hydrolysis, some treatments with this compound reduced NH3 losses and increased grain yields by up to 31%.
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    Biogeochemistry 33 (1996), S. 125-146 
    ISSN: 1573-515X
    Keywords: Denitrification ; stream ecology ; nutrient dynamics ; nitrification ; hyporheic zone ; parafluvial zone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Denitrification was measured in hyporheic, parafluvial, and bank sediments of Sycamore Creek, Arizona, a nitrogen-limited Sonoran Desert stream. We used three variations of the acetylene block technique to estimate denitrification rates, and compared these estimates to rates of nitrate production through nitrification. Subsurface sediments of Sycamore Creek are typically well-oxygenated, relatively low in nitrate, and low in organic carbon, and therefore are seemingly unlikely sites of denitrification. However, we found that denitrification potential (C & N amended, anaerobic incubations) was substantial, and even by our conservative estimates (unamended, oxic incubations and field chamber nitrous oxide accumulation), denitrification consumed 5–40% of nitrate produced by nitrification. We expected that denitrification would increase along hyporheic and parafluvial flowpaths as dissolved oxygen declined and nitrate increased. To the contrary, we found that denitrification was generally highest at the upstream ends of subsurface flowpaths where surface water had just entered the subsurface zone. This suggests that denitrifiers may be dependent on the import of surface-derived organic matter, resulting in highest denitrification rate at locations of surface-subsurface hydrologic exchange. Laboratory experiments showed that denitrification in Sycamore Creek sediments was primarily nitrogen limited and secondarily carbon limited, and was temperature dependent. Overall, the quantity of nitrate removed from the Sycamore Creek ecosystem via denitrification is significant given the nitrogen-limited status of this stream.
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