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  • Articles  (218)
  • Nitrification  (94)
  • Rhizosphere  (66)
  • Holocene  (60)
  • Springer  (218)
  • Geosciences  (218)
  • 1
    Electronic Resource
    Electronic Resource
    Effect of bamboo harvest on dynamics of nutrient pools, N mineralization, and microbial biomass in soil (1994)
    Springer
    Biology and fertility of soils 18 (1994), S. 137-142 
    Details
    ISSN: 1432-0789
    Keywords: Microbial biomass ; Bamboo savanna ; N mineralization ; Nutrient pools ; Temporal variations ; Nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of harvesting bamboo savanna on the dynamics of soil nutrient pools, N mineralization, and microbial biomass was examined. In the unharvested bamboo site NO inf3 sup- -N in soil ranged from 0.37 to 3.11 mg kg-1 soil and in the harvested site from 0.43 to 3.67 mg kg-1. NaHCO3-extractable inorganic P ranged from 0.55 to 3.58 mg kg-1 in the unharvested site and from 1.01 to 4.22 mg kg-1 in the harvested site. Over two annual cycles, the N mineralization range in the unharvested and harvested sites was 0–19.28 and 0–24.0 mg kg-1 soil month-1, respectively. The microbial C, N, and P ranges were 278–587, 28–64, and 12–26 mg kg-1 soil, respectively, with the harvested site exhibiting higher values. Bamboo harvesting depleted soil organic C by 13% and total N by 20%. Harvesting increased N mineralization, resulting in 10 kg ha-1 additional mineral N in the first 1st year and 5 kg ha-1 in the 2nd year following the harvest. Microbial biomass C, N and P increased respectively by 10, 18, and 5% as a result of bamboo harvesting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336460
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  • 2
    Electronic Resource
    Electronic Resource
    Dynamics of mineral nitrogen in soils supporting potato crops (1995)
    Springer
    Biology and fertility of soils 19 (1995), S. 36-40 
    Details
    ISSN: 1432-0789
    Keywords: Soil nitrogen ; Immobilisation ; Mineralisation ; Nitrification ; Solanum tuberosum L. ; Plant effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Following application of fertiliser-N to the seedbed of potato crops, concentrations of extracted mineral-N were up to 3 times greater than would be anticipated by calculation. The rates at which both NO 3 − -N and NH 4 + -N apparently appeared and disappeared in the soil solution were, at various times, also much greater than could be attributable to any transformations resulting from microbial activity. This suggests that the involvement of other factors in this phenomenon must be considered. The effect of certain physical parameters such as water movement, resulting from capillary action and evaporation from the soil surface, may be implicated. We suggest that soil microbes are not directly involved in the early fate of fertiliser-N, primarily due to C-limitation in arable soils. N dynamics in fertilised potato systems require further studies targeting the relationships between nutrient concentrations in soil solution and mass flow of soil water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336344
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  • 3
    Electronic Resource
    Electronic Resource
    Nitrification of ammonium in different components of a flooded rice soil system (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 321-326 
    Details
    ISSN: 1432-0789
    Keywords: Nitrification ; Flooded rice soils ; Rhizosphere ; Rice variety ; Crop growth stage ; Organic amendment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nitrification associated with the various components [subsurface soil from unplanted and planted (rhizosphere) fields, standing water and surface soil from planted and unplanted fields and leaf sheath suspensions] of submerged rice paddies was examined in incubation experiments with solutions inoculated with soil or water samples. Substantial nitrification occurred in all samples, standing water and surface soil samples in particular, during their 40-day incubation with NH 4 + −N. Almost all the NH 4 + −N, disappeared during incubation with standing water, was recovered as NO inf3 sup- −N. This, compared to 70–80% from all soil samples and only 29% from leaf sheath suspensions. Significant loss of nitrogen, especially from leaf sheath suspensions, is probably due to nitrification-denitrification as evidenced by its complete recovery in the presence of N-Serve. Nitrification potential of the soil and water samples varied with the crop growth stage and was more pronounced at tillering and panicle inititation stages than at other stages. Nitrification potential of samples from green-manure-amended plots was distinctly less than that of samples from control and urea-amended plots. Most probable number (MPN) estimates of ammonium-oxidizing bacteria were always higher in surface soil in both planted and unplanted plots at all stages of crop growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335961
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  • 4
    Electronic Resource
    Electronic Resource
    Microbial biomass and activity in soil and litter under Pinus sylvestris, Picea abies and Betula pendula at originally similar field afforestation sites (1996)
    Springer
    Biology and fertility of soils 24 (1996), S. 45-51 
    Details
    ISSN: 1432-0789
    Keywords: Key words Forest soil ; Tree species ; Pinus sylvestris L. ; Picea abies L. ; Betula pendula L. ; Field afforestation ; Microbial biomass C ; Microbial biomass N ; Microbial ; respiration ; Ammonification ; Nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Microbial biomass C and N, and activities related to C and N cycles, were compared in needle and leaf litter, and in the uppermost 10 cm of soil under the litter layer in Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies L.) and silver birch (Betula pendula L.) stands, planted on originally similar field afforestation sites 23–24 years ago. The ground vegetation was differentiated under different tree species, consisting of grasses and herbs under birch and pine, and mosses or no vegetation with a thick layer of needles under spruce. The C:N ratio of the soils was 13–21 and the soil pHCaCl2 3.8–5.2. Both showed little variation under different tree species. Microbial biomass C and N, C mineralization, net ammonification, net nitrification and N2-fixing activity (acetylene reduction) did not differ significantly in soil under different tree species either. Birch leaf litter had a higher pHCaCl2 (5.9) than spruce and pine needle litter (pH 5.0 and 4.8, respectively). The C:N ratio of spruce needles was 30, and was considerably higher in pine needles (69) and birch leaves (54). Birch leaves tended to have the highest microbial biomass C and C mineralization. Spruce needles appeared to have the highest microbial biomass N and net formation of mineral N, whereas formation of mineral N in pine needles and birch leaves was negligible. Microbial biomass C and N were of the same order of magnitude in the soil and litter samples but C mineralization was tenfold higher in the litter samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01420219
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  • 5
    Electronic Resource
    Electronic Resource
    Estimating microbial biomass N in soils with and without living roots: Limitations of a pre-extraction step (1996)
    Springer
    Biology and fertility of soils 21 (1996), S. 314-318 
    Details
    ISSN: 1432-0789
    Keywords: Microbial biomass N ; Fumigation-extraction ; Pre-extraction ; Rhizosphere ; Roots ; Net-closed soil containers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Special net-closed soil containers were used in a pot experiment with low and high plant densities to give soil samples with and without roots. Soils from the containers were analysed either by the fumigation-extraction method or by a modified procedure starting with a pre-extraction and sieving step to remove plant roots from the samples. In the extracts NO 3 - -N, NH 4 + -N, organic N, and total N were measured. Microbial biomass N was calculated from the differences in total N in fumigated and unfumigated soils. Different plant densities had almost no influence on the values of the N compounds using either method. In soils with roots, significantly more organic N (and total N) was found by the fumigation-extraction method compared to soils without roots while no differences were obtained using pre-extractions and sieving. Though the organic N content in pre-extracts from soils with roots was significantly higher than from soils without roots, the NO 3 - -N and NH 4 + -N content was lower. Significant differences in biomass N in soils with and without roots were found only with the fumigation-extraction method. Biomass N levels calculated using the results after pre-extraction and sieving were about 50% lower than levels detected using fumigation-extraction alone. With the use of special net-closed soil containers, not only were soil samples produced with and without roots, but it was also possible to induce a rhizophere in the soils. A comparison of the two methods using these soils clearly demonstrated that the method used has profound influence on the final biomass N results. While higher “biomass” levels were found by fumigation-extraction in soils with roots, because root N becomes extractable after fumigation, the use of a pre-extraction and a sieving step may underestimate the total biomass N content due to the pre-extraction of microbial N (especially from rhizosphere microorganisms) from the sample. Nevertheless, pre-extraction and sieving followed by fumigation-extraction does seem to be the preferable method for biomass N measurement in comparative studies, because in most cases only minor errors will occur.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334909
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  • 6
    Electronic Resource
    Electronic Resource
    Mineralization of carbon and nitrogen, and nitrification in Scots pine forest soil treated with fast- and slow-release nitrogen fertilizers (1996)
    Springer
    Biology and fertility of soils 22 (1996), S. 214-220 
    Details
    ISSN: 1432-0789
    Keywords: Key words Dicyandiamide ; Forest soil ; Mineralization ; Nitrification ; Urea ; Urea-formaldehyde
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We studied the effects of fast- and slow-release organic N fertilizers (urea and urea-formaldehyde, Nitroform) on mineralization, nitrification, and N leaching in an acid, poor forest soil. We also studied the effects of a nitrification inhibitor (dicyandiamide) applied together with urea. Net nitrification, mineralization of N and C were determined by aerobic laboratory incubation of soil samples taken one and three growing seasons after N application. Numbers of autotrophic nitrifiers were estimated by a most probable number method three growing seasons after the treatment. Urea increased the CO2 production immediately after application, but after three growing seasons, CO2 production was the lowest in the urea-treated soils. In the nitroform-treated soils, the concentration of exchangeable NH4 + after the first and third growing seasons was of the same magnitude, in contrast to the urea-treated soils, where hydrolysis took place immediately. Three growing seasons after application, the highest amount of NH4 + accumulated during the laboratory incubation was in the nitroform-treated soils. Unlike urea, nitroform did not increase the production of NO3 – or the number of NH4 + oxidizers. In the urea+dicyandiamide-treated soils there was less NO3 – and a lower number of nitrifiers than in the urea-treated soils. The results showed that a slow-release N fertilizer, such as nitroform, increases the availability of mineral N in acid forest soils without increasing nitrification and hence the risk of NO3 – leaching.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00382515
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  • 7
    Electronic Resource
    Electronic Resource
    Nitrification and denitrification in the rhizosphere of rice: the detection of processes by a new multi-channel electrode (2000)
    Springer
    Biology and fertility of soils 31 (2000), S. 427-435 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003749900190
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  • 8
    Electronic Resource
    Electronic Resource
    Measurement of pH at the root surface of red clover (Trifolium pratense) grown in soils differing in proton buffer capacity (1988)
    Springer
    Biology and fertility of soils 5 (1988), S. 295-298 
    Details
    ISSN: 1432-0789
    Keywords: pH measurement ; Rhizosphere ; SB electrodes ; Proton secretion of roots ; Red clover ; Rhizotrone ; Rhizobium spp.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Measurements of pH were made at the root surface of Trifolium pratense, using Sb electrodes. Nodulated plants were grown in rhizotrones on a sandy soil free of carbonate and on a clay soil rich in carbonate. In the sandy soil, pH at the surface of root laterals was about 1 unit lower than in the bulk soil. The lowest pH values were found at the root tips. In the calcareous soil, pH measured at the root surface did not differ from pH in the bulk soil. This soil had a much higher H+ buffer capacity than the sandy soils. It seems likely that H+ ions excreted from the roots grown in the calcareous soil were directly neutralized by soil carbonate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00262134
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  • 9
    Electronic Resource
    Electronic Resource
    Nitrous oxide emissions from fertilised grassland: A 2-year study of the effects of N fertiliser form and environmental conditions (1997)
    Springer
    Biology and fertility of soils 25 (1997), S. 252-260 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050311
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  • 10
    Electronic Resource
    Electronic Resource
    Detection of nitrification in a stagnohumic-gley soil (1989)
    Springer
    Biology and fertility of soils 8 (1989), S. 335-338 
    Details
    ISSN: 1432-0789
    Keywords: Autotrophy ; Lime ; Lolium perenne ; Nitrate reductase ; Nitrification ; Stagnohumic gley
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Three different nitrification assays (short-term nitrifier activity, assimilatory nitrate reductase activity of Lolium perenne, and nitrate accumulation in the absence of plants) were performed either on soil from a naturally acidic stagnohumic-gley or on leaves from L. perenne grown in this soil. Before the investigation the soil was limed and fertilised in a manner consistent with established agricultural pasture improvement strategies. Short-term nitrifier activity was only detected in soils above pH 5.6. However, nitrate reductase activity and nitrate accumulation both showed a near linear increase between soil pH 3.8 and 6.8. These findings are attributed to the nature of the assays, each of which considers a different component of the soil nitrifier population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00263165
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  • 11
    Electronic Resource
    Electronic Resource
    Azospirillum — plant root associations: A review (1989)
    Springer
    Biology and fertility of soils 8 (1989), S. 356-368 
    Details
    ISSN: 1432-0789
    Keywords: Plant-root associations ; Azospirillum spp ; Rhizosphere ; Nitrogen fixation ; Acetylene reduction assay (ARA) ; Phytohormones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Bacteria of the genus Azospirillum are extensively studied for their plant-growth promoting effect following inoculation. Physiological and biochemical studies of these diazotrophic bacteria are now benefiting from recent breakthroughs in the development of genetic tools for Azospirilum. Moreover, the identification and cloning of Azospirillum genes involved in N2 fixation, plant interaction, and phytohormone production have given new life to many research projects on Azospirillum. The finding that Azospirillum genes can complement specific mutations in other intensively studied rhizosphere bacteria like Rhizobia will certainly trigger the exploration of new areas in rhizosphere biology. Therefore a review of the Azospirillum-plant interactions is particularly timely.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00263169
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  • 12
    Electronic Resource
    Electronic Resource
    Abiotic factors regulating nitrification in a Swedish arable soil (1989)
    Springer
    Biology and fertility of soils 8 (1989), S. 247-254 
    Details
    ISSN: 1432-0789
    Keywords: Nitrification ; Abiotic factors ; Ammonium concentration ; Vmax of nitrification ; Michaelis-Menten constant for ammonium oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effects of temperature, water potential and ammonium concentrations were studied in field and laboratory experiments on arable soil. The two field experiments used different sampling intervals, one at daily (short-term) and the other at monthly (long-term) intervals. In the short-term field experiment, the numbers and activities of nitrifiers were assessed before and after natural rain or irrigation. The nitrifiers were apparently outcompeted by heterotrophs during the first days after wetting the soil. Potential nitrification was affected only slightly by changes in water potential, whereas the numbers of ammonium and nitrite oxidizers appeared more sensitive to these changes. The numbers of ammonium and nitrite oxidizers correlated strongly during the daily samplings. The potential nitrite-oxidation rates correlated with water potentials whereas the potential ammonium oxidation rates did not. Extractable ammonium decreased in proportion to increasing nitrate concentrations in both the rain-fed and the irrigated plots. In the long-term field experiments, the numbers of ammonium oxidizers correlated with water potentials but not with in situ temperature or with ammonium concentrations. The potential ammonium-oxidation rates correlated with water potentials and with ammonium-oxidizer numbers. The potential nitrite-oxidation rates correlated strongly with the potential ammonium-oxidation rates. The field experiments implied that nitrite oxidizers obtained substrate from ammonium oxidizers but also from nitrate reduction. In laboratory experiments nitrate accumulated at a Q 10 of about 2 and the V max for nitrification was observed at a water potential of −0.11 MPa (65% of water-holding capacity). The K m for ammonium oxidation at pH 8.2 was 1.72 mg l−1 soil water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00266487
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  • 13
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    Denitrification in the rhizosphere of plants with inherently different aerenchyma formation: Wheat (Triticum aestivum) and rice (Oryza sativa) (1990)
    Springer
    Biology and fertility of soils 9 (1990), S. 215-219 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336228
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  • 14
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    Chitinolytic and proteolytic activity of streptomycetes isolated from root-free soil, rhizosphere and mycorrhizosphere of pine (Pinus sylvestris L.) (1990)
    Springer
    Biology and fertility of soils 9 (1990), S. 268-272 
    Details
    ISSN: 1432-0789
    Keywords: Streptomycetes ; Chitinolytic ; Proteolytic activity ; Soil ; Pine roots ; Rhizosphere ; Pinus sylvestris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary We tested 75 strains of Streptomyces spp. (25 taken from each environment of soil, rhizosphere, and mycorrhizosphere of pine, Pinus sylvestris L.) and all exhibited chitinolytic activity and hydrolysed gelatine and sodium caseinate in agar media. Enrichment of these media with glucose and NH4NO3 caused induction or stimulation of proteolytic Streptomyces spp. strains (80%) derived from root-free soil; inhibition of this activity was observed in most strains (92%) isolated from the root zone. The post-culture liquids of the rhizosphere strains cultured in the absence of glucose revealed a significantly higher proteolytic activity than those obtained from the root-free soil. The addition of glucose to the medium stimulated proteolytic activity in the post-culture broth of Streptomyces strains derived from soil and the mycorrhizosphere.
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    URL: http://dx.doi.org/10.1007/BF00336238
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  • 15
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    Urea losses in flooded soils with established oxidized and reduced soil layers (1990)
    Springer
    Biology and fertility of soils 9 (1990), S. 283-287 
    Details
    ISSN: 1432-0789
    Keywords: Nitrogen transformations ; Flooded soil ; Nitrogen loss ; Nitrification ; Dentitrification ; Urea ; NH3 volatilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Laboratory batch incubation experiments were conducted to determine in fate of urea-15N applied to floodwater of four rice soils with established oxidized and reduced soil layers. Diffusion-dependent urea hydrolysis was rapid in all soils, with rates ranging from 0.0107 to 0.0159 h-1 and a mean rate of 0.0131 h-1. Rapid loss of 53%–65% applied urea-15N occurred during the first 8 days after application, primarily by NH3 volatilization. At the end of 70 days, an additional 20%–30% of applied urea-15N was lost, primarily through nitrification-denitrification processes. The soil types showed significant differences in total applied urea-15 recovery. Conversion of urea-15N to N2-15N provided direct evidence of urea hydrolysis followed by nitrification-denitrification in flooded soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00634101
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  • 16
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    Methanotrophic bacteria in the rhizosphere of rice microcosms and their effect on porewater methane concentration and methane emission (1995)
    Springer
    Biology and fertility of soils 20 (1995), S. 93-100 
    Details
    ISSN: 1432-0789
    Keywords: Wetland rice ; Rhizosphere ; Gas diffusion probe ; Methane profiles ; Methane oxidation ; Microcosms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract CH4 emission from irrigated rice field is one of the major sources in the global budget of atmoshperic CH4. Rates of CH4 emission depend on both CH4 production in anoxic parts of the soil and on CH4 oxidation at oxic-anoxic interfaces. In the present study we used planted and unplanted rice microcosms and characterized them by numbers of CH4-oxidizing bacteria (MOB), porewater CH4 and O2 concentrations and CH4 fluxes. Plant roots had a stimulating effect on both the number of total soil bacteria and CH4-oxidizing bacteria as determined by fluorescein isothiocyanate fluorescent staining and the most probable number technique, respectively. In the rhizosphere and on the root surface CH4-oxidizing bacteria were enriched during the growth period of tice, while their numbers remained constant in unplanted soils. In the presence of rice plants, the porewater CH4 concentration was significantly lower, with 0.1–0.4mM CH4, than in unplanted microcosms, with 0.5–0.7mM CH4. O2 was detected at depths of up to 16 mm in planted microcosms, whereas it had disappeared at a depth of 2 mm in the unplanted experiments. CH4 oxidation was determined as the difference between the CH4 emission rates under oxic (air) and anoxic (N2) headspace, and by inhibition experiments with C2H2. Flux measurements showed varying oxic emission rates of between 2.5 and 29.0 mmol CH4m-2 day-1. An average of 34% of the anoxically emitted CH4 was oxidized in the planted microcosms, which was surprisingly constant. The rice rhizosphere appeared to be an important oxic-anoxic interface, significantly reducing CH4 emission.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336586
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    Gram-negative bacterial flora on the root surface of wheat (Triticum aestivum) grown under different soil conditions (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 273-281 
    Details
    ISSN: 1432-0789
    Keywords: Key words Wheat ; (Triticum aestivum) ; Rhizosphere ; Soil microflora ; Gram-negative bacteria ; API 20NE ; Flavobacterium spp. ; Cytophaga
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We identified 161 Gram-negative bacterial strains isolated from the root surface of wheat grown under different soil conditions. The strains were divided into seven groups based on major morphological and physiological properties. Taxonomic allocation of the groups was verified by guanine+cytosine contents of DNA. Except for one group, which may be assumed to include bacteria belonging to the genera Flavobacterium and Cytophaga, the various groups were taxonomically united. The distribution of the groups changed with soil improvement. Pseudomonads predominated in unimproved soil, but Flavobacterium and Cytophaga spp. were predominant in the most improved soil. As all the strains were non-fermentative by Hugh and Leifson‘s test, API 20NE identification was applied. However, many strains were misidentified by this system, especially in the Flavobacterium and Cytophaga spp. group. For ecological studies, the strains were classified to species level by the API 20 NE system and by the results of a combination of guanine+cytosine (mol%) and isoprenoid quinone data. The pattern of distribution of the bacteria on the root surface of wheat varied at species level within one genus depending on soil conditions.
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    URL: http://dx.doi.org/10.1007/BF00335955
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  • 18
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    Preservation of nitrifying capacity and nitrate availability in waterlogged soils by radial oxygen loss from roots of wetland plants (1995)
    Springer
    Biology and fertility of soils 20 (1995), S. 243-248 
    Details
    ISSN: 1432-0789
    Keywords: Radial O2 loss ; Nitrification ; Waterlogging ; Rumex thyrsiflorus ; Rumex palustris ; Nitrate reductase ; Redox potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of radial O2 loss from roots on nitrification and NO inf3 sup- availability were studied. Plants of the flooding-resistant species Rumex palustris and the flooding-sensitive species Rumex thyrsiflorus were grown on drained and waterlogged soils with an initially high nitrifying capacity. Nitrate reductase activity in the plant leaves was used as an indicator of NO inf3 sup- availability to the plants. In a separate experiment these species were shown to have higher levels of nitrate reductase activity when NO inf3 sup- was added to the soils compared to when only NH inf4 sup+ was provided. In drained soils nitrification was maintained and both plant species showed relatively high nitrate reductase activities in their leaves. In the water-logged series planted with R. thyrsiflorus, nitrification was inhibited, NH inf4 sup+ accumulated, and the plants grew less well compared to those on drained soils. In contrast, waterlogged soils planted with R. palustris had a redox potential high enough for O2 to be continuously replenished. Furthermore, the nitrifying capacity of these latter soils was maintained at a high level. R. palustris grew well and NO inf3 sup- must have been available to the plant, since a high level of nitrate reductase activity was observed in the leaves.
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    URL: http://dx.doi.org/10.1007/BF00336084
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    Endomycorrhizae in a newly cultivated acidic meadow: Effects of three years of barley cropping, tillage, lime, and phosphorus on root colonization and soil infectivity (1996)
    Springer
    Biology and fertility of soils 21 (1996), S. 160-165 
    Details
    ISSN: 1432-0789
    Keywords: Key words Hordeum vulgare ; Agricultural ecosystem ; Acidic soil ; Soil infectivity ; Endomycorrhizae ; Reduced tillage ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The dynamics of mycorrhizae under disturbance created by crop production is not well understood. A 3-year experiment was undertaken on a nutrient-poor and acidic land that had last been cultivated in the early 1970s. We observed the effects of cropping spring barley (Hordeum vulgare L.) under four P-fertilizer levels and four levels of lime, in a minimum (rototillage), a reduced (chisel), or a conventional tillage system, on the mycorrhizal receptiveness of the host (maximum level of mycorrhizal colonization, as measured at harvest) and soil infectivity most probable number method. The host receptiveness decreased with time, while crop yields and soil infectivity increased simultaneously with time. Liming increased mycorrhizal colonization of barley roots and soil infectivity. P additions decreased root colonization but did not significantly affect the most probable number values. Slightly higher soil infectivity estimates were found under reduced tillage.
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    URL: http://dx.doi.org/10.1007/BF00335928
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  • 20
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    Solubilization of hydroxyapatite by Enterobacter agglomerans and cloned Escherichia coli in culture medium (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 347-352 
    Details
    ISSN: 1432-0789
    Keywords: Key words Phosphate-solubilizing bacteria ; Hydroxyapatite ; Enterobacter agglomerans ; Organic acids ; Phosphate-solubilizing genes ; Rhizosphere ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phosphate-solubilizing bacteria (PSB) possessing the ability to solubilize insoluble inorganic phosphate were isolated from the rhizosphere soil of wheat. A laboratory study was conducted to investigate the solubilization of phosphate by a known PSB, Enterobacter agglomerans, and by a genetically manipulated bacterium, Escherichia coli. A second laboratory study investigated the release of P from E. agglomerans compared with known acids. For the first laboratory study, a cosmid (pHC79) library of phosphate-solubilizing gene(s) from E. agglomerans chromosome DNA was constructed in E. coli JM109. The clone JM109 (pKKY) showing phosphate solubilization properties was screened on standard medium containing hydroxyapatite (HY). The P concentration significantly increased at 5 and 10 days for JM109 (pKKY) compared with JM109 (pHC79), the control. Although the P concentration increased, there was no significant change in their pHs. Furthermore, an increase in colony-forming units (CFUs) was seen at 5 and 10 days for JM109 (pKKY) but not for JM109 (pHC79). Artificial acidification of the culture medium with HCl, citric acid, oxalic acid, and lactic acid was achieved by shaking for 48h. Acidification with these selected acids solubilized more HY than E. agglomerans growing for 42h at similar pHs. However, a high P concentration was measured in culture medium with E. agglomerans growing for 84h despite similar pHs. Our results suggest that acid production may play an important role in HY solubilization, but is not the sole reason for the increase in P concentration in culture medium.
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    URL: http://dx.doi.org/10.1007/s003740050256
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  • 21
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    Relative importance of motility and antibiosis in the rhizoplane competence of a biocontrol agent Pseudomonas fluorescens MelRC2Rif (1997)
    Springer
    Biology and fertility of soils 25 (1997), S. 416-420 
    Details
    ISSN: 1432-0789
    Keywords: Key wordsPseudomonas fluorescens ; MelRC2Rif ; Motility ; Antibiosis ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Mutants defective in motility or antibiotics production were obtained by Tn5 mutagenesis of a biocontrol agent Pseudomonas fluorescens MelRC2Rif (wt). Tomato or melon seeds were co-inoculated with a Tn5 mutant and wt in a 1:1 ratio and then grown in soil for 10 days. There was no change in ratios of Tn5 mutants defective in antibiosis to wt in the process of rhizoplane colonization, suggesting little contribution of in vitro antibiosis to the rhizoplane competence of P. fluorescens MelRC2Rif. Similar results were also obtained when seeds treated with bacteria were planted in soil artificially infested with fungal pathogens. In contrast, ratios of Tn5 mutants defective in motility to wt significantly decreased, suggesting the contribution of motility to the rhizoplane competence of this bacterium. When a non-motile Tn5 mutant and wt were co-inoculated into soil at a matric potential of pF 2.3 (–20 kPa) and plants were then grown, there was no change in the ratio in rhizoplane colonization, suggesting that motility might have a role in the movement along roots but an insignificant role in the movement from bulk soil towards roots. When they were co-inoculated into 0.2% water agar (WA) instead of soil, a remarkable decline in ratios was detected. Thus it was soil structure that hindered the efficiency of motility. Time course enumeration of rhizoplane colonization of tomatoes grown in WA revealed that motility was an important means of movement towards and/or along roots rather than the multiplication on roots.
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    URL: http://dx.doi.org/10.1007/s003740050334
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    Phosphatase activity in the rhizosphere and its relation to the depletion of soil organic phosphorus (1987)
    Springer
    Biology and fertility of soils 3 (1987), S. 199-204 
    Details
    ISSN: 1432-0789
    Keywords: Phosphatases ; Rhizosphere ; Organic phosphorus ; Allium cepa ; Brassica oleracea ; Triticum aestivum ; Trifolium alexandrinum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The distribution of phosphatase activity and of phosphate fractions of the soil in the proximity of roots was studied in order to evaluate the significance of phosphatases in P nutrition of various plants (Brassica oleracea, Allium cepa, Triticum aestivum, Trifolium alexandrinum). A considerable increase in both acid and alkaline phosphatase activity in all the four soil-root interfaces was observed. Maximum distances from the root surface at which activity increases were observed ranged from 2.0 mm to 3.1 mm for acid phosphatase and from 1.2 mm to 1.6 mm for alkaline phosphatase. The increase in phosphatase activity depended upon plant age, plant species and soil type. A significant correlation was noticed between the depletion of organic P and phosphatase activity in the rhizosphere soil of wheat (r = 0.99**) and clover (r = 0.97**). The maximum organic P depletion was 65% in clover and 86% in wheat, which was observed within a distance from the root of 0.8 mm in clover and 1.5 mm in wheat. Both the phosphatases in combination appear to be responsible for the depletion of organic P.
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    URL: http://dx.doi.org/10.1007/BF00640630
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    Comparing microbial biomass, denitrification enzyme activity, and numbers of nitrifiers in the rhizospheres of Pinus sylvestris, Picea abies and Betula pendula seedlings by microscale methods (1999)
    Springer
    Biology and fertility of soils 30 (1999), S. 14-19 
    Details
    ISSN: 1432-0789
    Keywords: Key words Tree species ; Rhizosphere ; Microbial biomass ; Denitrification enzyme activity ; Autotrophic nitrifiers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Flushes of C and N from fumigation-extraction (FE-C and FE-N, respectively), substrate-induced respiration (SIR), denitrification enzyme activity (DEA) and numbers of NH4 + and NO2 – oxidizers were studied in the rhizospheres of Scots pine (Pinus sylvestris L.), Norway spruce [(Picea abies (L.) Karsten] and silver birch (Betula pendula Roth) seedlings growing in soil from a field afforestation site. The rhizosphere was defined as the soil adhering to the roots when they were carefully separated from the rest of the soil in the pots, termed as "planted bulk soil". Soil in unplanted pots was used as control soil. All seedlings had been grown from seed and had been infected by the natural mycorrhizas of soil. Overall, roots of all tree species tended to increase FE-C, FE-N, SIR and DEA compared to the unplanted soil, and the increase was higher in the rhizosphere than in the planted bulk soil. In the rhizospheres tree species did not differ in their effect on FE-C, FE-N and DEA, but SIR was lowest under spruce. In the planted bulk soils FE-C and SIR were lowest under spruce. The planted bulk soils differed probably because the roots of spruce did not extend as far in the pot as those of pine and birch. The numbers of both NH4 + and NO2 –oxidizers, determined by the most probable number method, were either unaffected or decreased by roots, with the exception of the spruce rhizosphere, where numbers of both were increased.
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    URL: http://dx.doi.org/10.1007/s003740050581
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    The "oxygen paradox" of dinitrogen-fixing bacteria (2000)
    Springer
    Biology and fertility of soils 30 (2000), S. 363-373 
    Details
    ISSN: 1432-0789
    Keywords: Key words Azospirillum species ; Oxygen paradox ; Nitrogen fixation ; Rhizosphere ; Nitrogenase complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  N2 fixation by aerobic bacteria is a very energy demanding process, requiring efficient oxidative phosphorylation, while O2 is toxic for the nitrogenase complex. N2-fixing bacteria have evolved a variety of strategies to cope with this apparent "O2 paradox". This review compares strategies that azospirilla and other well-known N2-fixing soil bacteria use to overcome this O2 paradox. Attention will be given to the relationships between the natural habitat of these soil bacteria and their prevailing adaptations. In view of this knowledge the following questions will be addressed: are the specific adaptations observed in azospirilla sufficient to allow optimal proliferation and N2 fixation in their natural habitat? Could improving the O2 tolerance of the N2-fixing process contribute to the development of more efficient strains for the inoculation of plants?
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    URL: http://dx.doi.org/10.1007/s003740050017
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    Microsensor analysis of oxygen and pH in the rice rhizosphere under field and laboratory conditions (1999)
    Springer
    Biology and fertility of soils 29 (1999), S. 379-385 
    Details
    ISSN: 1432-0789
    Keywords: Key words Oxygen ; pH ; Rhizosphere ; Microsensor ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  O2 and pH microsensors were used to analyse the microdistribution of O2 and pH inside and outside roots of lowland rice (Oryza sativa L.). The roots of 3-week-old transplants had O2 concentrations of about 20% air saturation at the surface, but due to a high rate of O2 consumption in the rhizosphere, the oxic region only extended about 0.4 mm into the surrounding soil. Also the fine lateral roots created an oxic zone extending about 0.15 mm into the soil. The O2 concentration within the roots approached air saturation close to the base, but only about 40–60% of air saturation in a region about 8 cm below the base where lateral rootlets were present. A shift from air to N2 around the leaves led to a drop of 50% in the O2 concentration after 12 min at a distance of 8.5 cm from the base. Flowering plants did not export O2 to the soil from the majority of their roots, but high microbial activity was present in a very thin biofilm covering the root surface. A brown colour around the thin lateral roots indicated some O2 export from these also during flowering. No oxidized zone was present around the roots at later stages of crop growth. The roots caused only minor minima in pH (〈0.2 pH units) in the rhizosphere as compared to the bulk soil. Illumination of the plants had no effect on rhizosphere pH.
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    Effects of salts and moisture content on N2O emission and nitrogen dynamics in Yellow soil and Andosol in model experiments (1999)
    Springer
    Biology and fertility of soils 29 (1999), S. 401-407 
    Details
    ISSN: 1432-0789
    Keywords: Key words Andosols ; N2O ; Nitrification ; N mineralization ; Yellow soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The effects of salt type and its concentration on nitrification, N mineralization and N2O emission were examined under two levels of moisture content in Yellow soil and Andosol samples as simulated to agriculture under arid/semi-arid conditions and under heavy application of fertilizer in a glass-house, respectively. The salt mixtures were composed of chlorides (NaCl and NH4Cl) or sulphates [Na2SO4 and (NH4)2SO4] and were added at various concentrations (0, 0.1, 0.2, 0.4 and 0.6 M as in the soil solution). These salts were added to non-saline Yellow soil at different moisture contents (45 or 40 and 65% of maximum water-holding capacity; WHC) and their effects on the changes in mineral N (NH4 +-N and NO3 –-N) concentration as well as N2O emission were examined periodically during laboratory incubation. We also measured urease activities to know the effect of salts on N mineralization. Furthermore, Ca(NO3)2 solution was added at various concentrations (0, 0.1, 0.3, 0.5 and 0.8 M as in the soil solution) to a non-saline Andosol taken from the subsurface layer in a glass-house and incubated at different moisture contents (50% and 70% of WHC) to examine their effects on changes in mineral N. Nitrification was inhibited by high, but remained unaffected by low, salt concentrations. These phenomena were shown in both the model experiments. It was considered that the salinity level for inhibition of nitrification was an electric conductivity (1 : 5) of 1 dS m–1. This level was independent of the type of salts or soil, and was not affected by soil moisture content. The critical level of salts for urease activities was about 2 dS m–1. The emission rate of N2O was maximum at the beginning of the incubation period and stabilized at a low level after an initial peak. There was no significant difference in N2O emission among the treatments at different salt concentrations, while higher moisture level enhanced N2O emission remarkably.
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    URL: http://dx.doi.org/10.1007/s003740050571
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    Nitrogen monoxide production and consumption in an organic soil (1999)
    Springer
    Biology and fertility of soils 30 (1999), S. 153-159 
    Details
    ISSN: 1432-0789
    Keywords: Key words Denitrification ; Nitric Oxide ; Nitrification ; Nitrogen Monoxide ; Nitrous Oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Factors controlling NO production, consumption, and emission rates were examined in an organic soil. Emission rates were measured in the enclosed headspaces of intact soil cores under three fertilisation treatments (unfertilised or 100 kg N ha–1 as NH4Cl or as NaNO3), with and without the nitrification inhibitor C2H2 (20–70 μl l–1). Nitrification was always the main source of NO emitted across the soil surface, even when the soil was nearly saturated. Fertilisation of soil with NH4Cl increased NO emission both by stimulating NO production from nitrification, and by decreasing the NO consumption rate constant. Addition of NaNO3 also stimulated the production of NO and N2O during nitrification in aerobic soil slurry experiments. This effect was eliminated by adding C2H2 and was therefore not related to denitrification. In loose soil samples, the increase in NO-N production after NH4Cl addition represented as much as 26% of the added N. However, in intact cores, 95% of the NO produced through nitrification was oxidised within the soil column rather than emitted to the atmosphere. We concluded that nitrification is the primary NO source from this organic soil, that surface NO emissions are much lower than gross NO production rates, and that gaseous N oxide (NO and N2O) losses during nitrification can be affected by both soil NH4 + and NO3 –.
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    URL: http://dx.doi.org/10.1007/s003740050602
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    Nitrogen and oxygen isotope ratios of nitrous oxide emitted from soil and produced by nitrifying and denitrifying bacteria (1996)
    Springer
    Biology and fertility of soils 22 (1996), S. 326-330 
    Details
    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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    Contributions from different microbial processes to N2O emission from soil under different moisture regimes (1996)
    Springer
    Biology and fertility of soils 22 (1996), S. 331-335 
    Details
    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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    URL: http://dx.doi.org/10.1007/BF00334578
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    Effect of the inhibitors nitrapyrin and sodium chlorate on nitrification and N2O formation in an acid forest soil (1996)
    Springer
    Biology and fertility of soils 22 (1996), S. 318-325 
    Details
    ISSN: 1432-0789
    Keywords: Autotrophs ; Liming ; Nitrapyrin ; N-serve ; Nitrification ; N2O ; Sodium chlorate ; Acid beech forest soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An acid forest soil from beech forest gaps, which were either limed or unlimed, and the undisturbed forest was investigated for the type of nitrifying populations and the process of N2O evolution. To see whether nitrifiers were of heterotrophic or autotrophic origin, the nitrification inhibitors nitrapyrin and sodium chlorate were applied to disturbed soil samples which underwent laboratory incubations. Nitrapyrin inhibits autotrophic nitrification. In different studies, sodium chlorate has been identified as an inhibitor either of autotrophic or of heterotrophic nitrification. In the samples investigated only nitrapyrin inhibited the autotrophic nitrification occurring in the limed soil. Sodium chlorate effectively inhibited heterotrophic nitrification. In the limed forest floor samples, where most autotrophic nitrification occured, sodium chlorate showed no inhibitory effect. In another laboratory incubation experiment, N2O evolution from undisturbed soil columns, to which the above inhibitors were applied, was investigated. In those samples, in which nitrification had been reduced, neither inhibitor significantly reduced N2O evolution. Thus it was concluded that the contribution of nitrification to N2O losses is negligible, and that N2O evolution arises from the activity of denitrifying organisms. Microbial biomass and respiration measurements showed that the inhibitors did not affect microflora negatively.
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    Soil pH changes during legume growth and application of plant material (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 236-242 
    Details
    ISSN: 1432-0789
    Keywords: Key words Soil pH ; Legume ; Alkalinity ; Decarboxylation ; Ammonification ; Vicia faba L. ; Nitrification ; Zea mays L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract During cultivation of legumes soil is acidified due to proton release from roots. As a consequence of proton release, plants accumulate organic anions which may, if returned and decomposed in the soil, neutralize the soil acids. Until now the detailed processes responsible for the change in soil pH after incorporation of plant material have not been completely understood. Using a pot experiment we studied the changes in acid and base in soil during growth of field beans (Vicia faba L. cv. Alfred) and after incorporation of the plant material into the soil. Soil pH was significantly decreased by field beans from 6.00 to 5.64 in a cultivation period of 45 days. Proton release amounted to 32.7 mmol H+ pot–1, which was approximately equivalent to the accumulated alkalinity in the plant shoots (34.4 mmol). Return of field bean shoots caused a significant soil pH increase from 5.64 to 6.29. Within 7 days more than 90% of the added alkalinity was released. After 307 days incubation, soil pH decreased to 5.86 due to nitrification. In a second experiment, maize leaves (Zea mays L.), containing various concentrations of nitrogen and at various alkalinities, were incorporated into the soil. Soil pH change was positively correlated to alkalinity and malate concentration and negatively correlated to total nitrogen and water-soluble organic nitrogen of incorporated leaves. It is concluded that the soil acidification caused by legume cultivation can be partly compensated for if crop residues are returned to the soil. Addition of plant material may initially cause an increase in soil pH due to decomposition of organic anions and organic nitrogen. Soil pH may decrease if nitrification is involved. The concentrations of nitrogen and alkalinity of added plant material are decisive factors controlling soil pH change after incorporation of plant material.
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    Effect of bulk density and soil water tension on denitrification in the rhizosphere of spring wheat (Triticum vulgare (1987)
    Springer
    Biology and fertility of soils 5 (1987), S. 181-187 
    Details
    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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    Factors controlling nitrogen mineralization and nitrification in forest ecosystems in New Mexico (1987)
    Springer
    Biology and fertility of soils 5 (1987), S. 195-202 
    Details
    ISSN: 1432-0789
    Keywords: Nitrogen mineralization ; Nitrification ; Organic quality ; New Mexico
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Forest floor and mineral soil from ponderosa-pine, Douglas-fir, aspen and spruce-fir ecosystems located along a rising gradient in New Mexico were tested with laboratory assays for factors controlling N mineralization and nitrification. We concluded that low pH in combination with factors associated with organic quality controlled N mineralization and almost completely limited nitrification in spruce-fir soils, while N mineralization in the forest floor of ponderosa-pine was limited by low nutrient availability (other than N). Organic quality of the substrate and temporal changes in organic quality appeared to control N-mineralization and nitrification processes in forest-floor and mineral soils from all other sites.
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    Microbial biomass and activity in soil and litter underPinus sylvestris, Picea abies andBetula pendula at originally similar field afforestation sites (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 45-51 
    Details
    ISSN: 1432-0789
    Keywords: Forest soil ; Tree species ; Pinus sylvestris L. ; Picea abies L. ; Betula pendula L. ; Field afforestation ; Microbial biomass C ; Microbial biomass N ; Microbial respiration ; Ammonification ; Nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Microbial biomass C and N, and activities related to C and N cycles, were compared in needle and leaf litter, and in the uppermost 10 cm of soil under the litter layer in Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies L.) and silver birch (Betula pendula L.) stands, planted on originally similar field afforestation sites 23–24 years ago. The ground vegetation was differentiated under different tree species, consisting of grasses and herbs under birch and pine, and mosses or no vegetation with a thick layer of needles under spruce. The C:N ratio of the soils was 13–21 and the soil pHCaCl 2 3.8–5.2. Both showed little variation under different tree species. Microbial biomass C and N, C mineralization, net ammonification, reduction) did not differ significantly in soil under different tree species either. Birch leaf litter had a higher pHCaCl 2 (5.9) than spruce and pine needle litter (pH 5.0 and 4.8, respectively). The C:N ratio of spruce needles was 30, and was considerably higher in pine needles (69) and birch leaves (54). Birch leaves tended to have the highest microbial biomass C and C mineralization. Spruce needles appeared to have the highest microbial biomass N and net formation of mineral N, whereas formation of mineral N in pine needles and birch leaves was negligible. Microbial biomass C and N were of the same order of magnitude in the soil and litter samples but C mineralization was tenfold higher in the litter samples.
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    Nodulation competition among Bradyrhizobium japonicum strains as influenced by rhizosphere bacteria and iron availability (1989)
    Springer
    Biology and fertility of soils 7 (1989), S. 108-112 
    Details
    ISSN: 1432-0789
    Keywords: Bradyrhizobium japonicum ; Glycine max ; Soil inoculation ; Nodulation ; Rhizosphere ; Rhizobacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Bacteria isolated from the root zones of field-grown soybean plants [Glycine max (L.) Merr.] were examined in a series of glasshouse experiments for an ability to affect nodulation competition among three strains of Bradyrhizobium japonicum (USDA 31, USDA 110, and USDA 123). Inocula applied at planting contained competing strains of B. japonicum with or without one of eleven isolates of rhizosphere bacteria. Tap-root nodules were harvested 28 days after planting, and nodule occupancies were determined for the bradyrhizobia strains originally applied. Under conditions of low iron availability, five isolates (four Pseudomonas spp. plus one Serratia sp.) caused significant changes in nodule occupancy relative to the corresponding control which was not inoculated with rhizosphere bacteria. During subsequent glasshouse experiments designed to verify and further characterize these effects, three fluorescent Pseudomonas spp. consistently altered nodulation competition among certain combinations of bradyrhizobia strains when the rooting medium did not contain added iron. This alteration typically reflected enhanced nodulation by USDA 110. Two of these isolates produced similar, although less pronounced, effects when ferric hydroxide was added to the rooting medium. The results suggest that certain rhizosphere bacteria, particularly fluorescent Pseudomonas spp., can affect nodulation competition among strains of R. japonicum. An additional implication is that iron availability may be an important factor modifying interactions involving the soybean plant, B. japonicum, and associated microorganisms in the host rhizosphere.
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    URL: http://dx.doi.org/10.1007/BF00292567
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    Stimulation of root exudation of rice seedlings by Azospirillum strains: carbon budget under gnotobiotic conditions (1987)
    Springer
    Biology and fertility of soils 4 (1987), S. 9-14 
    Details
    ISSN: 1432-0789
    Keywords: Rhizosphere ; Nitrogen fixation ; Root exudates ; Soil bacteria ; Carbon budget ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The association of rice seedlings (cv. Delta) with different strains of Azospirillum was studied under monoxenic conditions in the dark. Axenic 3-day-old seedlings were obtained on a C- and N-free medium and inoculated with 6 · 107 bacteria per plant in a closed vial. Seven days later, different components of a carbon budget were evaluated on them and on sterile controls: respired CO2, carbon of shoot and roots, bacterial and soluble carbon in the medium. Two strains (A. lipoferum 4B and A. brasilense A95) isolated from the rhizosphere of rice caused an increase in exudation, + 36% and + 17% respectively compared with sterile control. Shoot carbon incorporation and respiration were reduced by inoculation. A third strain (A. brasilense R07) caused no significant change in exudation. A. lipoferum B7C isolated from maize did not stimulate rice exudation either. We further investigated a possible effect of nitrogen fixation on this phenomenon: inhibition of nitrogen fixation by 10% C2H2 did not modify the extent of C exudation by rice associated with A. lipoferum 4B or with the non-motile A. lipoferum 4T.
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    N dynamics and sources of N2O production following pig slurry application to a loamy soil (1998)
    Springer
    Biology and fertility of soils 26 (1998), S. 224-228 
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    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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    Long-term large N and immediate small N addition effects on trace gas fluxes in the Colorado shortgrass steppe (1998)
    Springer
    Biology and fertility of soils 28 (1998), S. 44-50 
    Details
    ISSN: 1432-0789
    Keywords: Key words Nitrous oxide ; Methane consumption ; Nitrification ; Oxides of nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Land use changes in semiarid grasslands have long-lasting effects. Reversion to near-original conditions with respect to plant populations and productivity requires more than 50 years following plowing. The impact of more subtle management changes like small, annual applications of N fertilizer or changing cattle stocking rates, which alters N redistribution caused by grazing and cattle urine deposition, is not known. To investigate the long-term effects of N addition to the Colorado shortgrass steppe we made weekly, year-round measurements of N2O and CH4 from the spring of 1990 through June 1996. Fluxes of NOx (NO plus NO2) were measured from October 1995 through June 1996. These measurements illustrated that large N applications, either in a single dose (45 g N m–2), simulating cattle urine deposition, or in small annual applications over a 15-year period (30 g N m–2) continued to stimulate N2O emissions from both sandy loam and clay loam soils 6–15 years after N application. In sandy loam soils last fertilized 6 years earlier, average NOx emissions were 60% greater than those from a comparable, unfertilized site. The long-term impact of these N additions on CH4 uptake was soil-dependent, with CH4 uptake decreased by N addition only in the coarser textured soils. The short-term impact of small N additions (0.5–2 g N m–2) on N2O, NOx emissions and CH4 uptake was observed in field studies made during the summer of 1996. There was little short-term effect of N addition on CH4 uptake in either sandy loam or clay loam soils. Small N additions did not result in an immediate increase in N2O emissions from the sandy loam soil, but did significantly increase N2O flux from the clay loam soil. The reverse soil type, N addition interaction occurred for NOx emissions where N addition increased NOx emissions in the coarser textured soil 10–20 times those of N2O.
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    Field method to determine N2O emission from nitrification and denitrification (1998)
    Springer
    Biology and fertility of soils 28 (1998), S. 51-55 
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    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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    A comparison of microbial-feeding nematodes and protozoa in the rhizosphere of different plants (1990)
    Springer
    Biology and fertility of soils 9 (1990), S. 83-88 
    Details
    ISSN: 1432-0789
    Keywords: Nematodes ; Protozoa ; Rhizosphere ; Nutrient cycling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The biomass of microbial-feeding nematodes and protozoa was measured in the rhizospheres of peas, barley, grass and turnips grown for 10 weeks in pots containing a clay-loam soil; in the rhizospheres of peas and barley grown for 3 weeks in a sandy soil; and in the rhizosphere of barley grown for 11 weeks in an unfertilised and a fertilised clay-loam soil. The nematode biomass was consistently larger in the rhizosphere of all plants in both soils than in the bulk soil, but the protozoa biomass showed a rhizosphere effect only under pea and fertilised barley. The biomass of nematodes in the rhizosphere (1.2–22.3 μg dry weight g-1 dry soil) was greater than the biomass of protozoa (0.1–3.2 μg g-1), and greater under pea〉barley〉grass〉turnip. It is suggested that nematodes are more able to exploit low bacterial densities than protozoa and that they initially migrate into the rhizosphere from the bulk soil. In samples of potato rhizosphere from field-grown plants, the nematode biomass was also greater than the active and total protozoan biomass. It is argued that in the rhizosphere the biomass of microbially feeding nematodes exceeds that of protozoa and that nematodes are more important in terms of nutrient cycling.
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    Short-term measurements of uptake of nitrogen fixed in the rhizospheres of sorghum (Sorghum bicolor) and millet (Pennisetum americanum) (1988)
    Springer
    Biology and fertility of soils 7 (1988), S. 11-15 
    Details
    ISSN: 1432-0789
    Keywords: 15N ; N2 fixation ; Rhizosphere ; Sorghum bicolor ; Pennisetum americanum ; Acetylene reduction assay (ARA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In a series of short-term experiments root systems of young sorghum and millet plants inoculated with N2-fixing bacteria were exposed to 15N2-enriched atmospheres for 72 h. The plants were grown in a normal atmosphere for up to 22 days after the end of the exposure to allow them to take up the fixed N2. Environmental conditions and genotypes of sorghum and millet were selected to maximise N2-fixation in the rhizosphere. Detectable amounts of fixed N (〉 16 μg/plant) were rapidly incorporated into sorghum plants grown in a sand/farmyard manure medium, but measurable fixation was found on only one occasion in plants grown in soil. N2 fixation was detectable in some experiments with soil-grown millet plants but the amounts were small (2–4 μg/plant) and represented less than 1 % of plant N accumulated over the same period. In many cases there was no detectable 15N2 incorporation despite measurable increases in ethylene concentration found during an acetylene reduction assay.
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    The microarthropod fauna associated with a deep rooted legume, Prosopis glandulosa, in the Chihuahuan Desert (1989)
    Springer
    Biology and fertility of soils 7 (1989), S. 330-335 
    Details
    ISSN: 1432-0789
    Keywords: Prosopis glandulosa ; Rhizosphere ; Mites ; Collembolans ; Chihuahuan Desert
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The rhizosphere microarthropod fauna of a woody, deep-rooted legume, Prosopis glandulosa, was sampled at four sites in the northern Chihuahuan Desert and compared with the rhizosphere microarthropod fauna of a co-dominant shrub, Larrea tridentata. Prostigmatid mites (Speleorchestes sp.,Neognathus sp., Rhagidia sp., Tydaeolus sp., Steneotarsonemus sp., Tarsonemus sp., Nanorchestes sp., Gordialycus sp.), the cryptostigmatid mites (Bankisonoma ovata and Passalozetes neomexicanus), the mesostigmatid (Protogamasellus mica), and the collembolan (Brachystomella arida) characterized the fauna at depths greater than 1 m. Microarthropods were recovered from soils at a depth of 13 m at the edge of a dry lake and at depths of 7 m in a dry wash which were pre-European man P. glandulosa habitats. In habitats where P. glandulosa is a recent invader, root depth and microarthropods were less than 3 m. In most habitats, population densites of microarthropods at depths 0.5 m were more than 100 times those at depths ≫ 0.5 m. Population densities of microarthropods associated with P. glandulosa growing at the edge of a dry wash were not significantly smaller at 0.5−1.0 m depth than at 0−0.5 m. The deep-rhizosphere microarthropod fauna is a reduced subset of the fauna of surficial soils, suggesting that this fauna plays a role in decomposition and mineralization processes functionally similar to that of microarthropods in surficial soils.
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    Distribution of microbial biomass across the rhizosphere of barley (Hordeum vulgare L.) in soils (1989)
    Springer
    Biology and fertility of soils 7 (1989), S. 341-345 
    Details
    ISSN: 1432-0789
    Keywords: ATP content ; Bulk soil ; CO2 production ; Mineral N ; Nitrification inhibitor ; Rhizosphere ; Sewage sludge ; Hordeum vulgare
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The microbial activity at the soil-root interface (rhizosphere) of barley was examined using a rhizobox system. In this system, the soil was placed in several compartments separated from each other by a 500-mesh nylon cloth. Plants were grown in the central compartment and after a 2-month growing period the roots were still confined to this compartment. The soil from each compartment was then analyzed for ATP, NO3 /−, total N, total C and CO2 production. The increase in ATP concentration was found in a range of 4 mm around the roots. The ATP content and CO2 production across the rhizosphere were correlated in all the soils used, but changes in NO3 − were not correlated with ATP changes. The range of NO3 − change was wider than that of the ATP change, indicating that NO3 − production is not influenced by the biological activity in the rhizosphere.
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    Growth and nitrogen nutrition of maize (Zea mays L.) in soil treated with the nitrification-inhibiting insecticide Baythroid (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 161-165 
    Details
    ISSN: 1432-0789
    Keywords: Key words ANI ; Baythroid ; Cyfluthrin ; Insecticide ; 15N ; Nitrification ; N uptake ; Synthetic pyrethroid ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A pot experiment was conducted to compare the uptake and dry matter production potential of NH+ 4 and NO– 3 and to study the effect of Baythroid, a contact poison for several insect pests of agricultural crops, on growth and N uptake of maize (Zea mays L.). Nitrogen was applied as (15NH4)2SO4, K15NO3, or 15NH4NO3 and in one treatment Baythroid was combined with 15NH4NO3. Source of N had, in general, a nonsignificant effect on dry matter and N yield, but uptake of NO– 3 was significantly higher than that of NH+ 4 when both N sources were applied together. Substantial loss of N occurred from both the sources, with NH+ 4 showing greater losses. Baythroid was found to have a significant positive effect on dry matter yield of both root and shoot; N yield also increased significantly. Uptake of N from both the applied and native sources increased significantly in the presence of Baythroid and a substantial added nitrogen interaction (ANI) was determined. The positive effect of Baythroid was attributed to: (1) a prolonged availability of NH+ 4 due to inhibition of nitrification, (2) an increased availability of native soil N through enhanced mineralization, and (3) an enhanced root proliferation.
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    Gram-positive bacterial flora on the root surface of wheat (Triticum aestivum L.) grown under different soil conditions (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 121-125 
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    ISSN: 1432-0789
    Keywords: Key words Wheat ; Rhizosphere ; Soil Microflora ; Gram-positive Bacteria ; Coryneform Bacteria ; Arthrobacter spp. ; Mol% G+C ; Diaminopimelic acid ; DAP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We identified 108 Gram-positive bacterial strains isolated from the root surface of wheat grown under different soil conditions. The strains were divided into four groups based on morphological and physiological characteristics, but most appeared to be coryneform. The taxonomic position of the various groups was verified by the guanine+cytosine DNA contents of the strains. In general, the ranges of these values agreed with those described for the respective taxonomic positions in the literature, with a few exceptions. With soil improvement the distribution of the various groups on the root surface changed, with the coryneform group becoming dominant. This group was further divided into five subgroups, according to cell wall components, cellulose-decomposition, and morphological characteristics, and were identified to genus level. The distribution of these subgroups on the root surface of wheat did not alter with soil improvement. The genus Arthrobacter, the dominant subgroup, predominated in every plot.
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    Azospirillum spp. participation in dry matter partitioning in grasses at the whole plant level (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 435-440 
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    ISSN: 1432-0789
    Keywords: Key wordsAzospirillum spp. ; Crop plants ; Plant growth-promoting rhizobacteria ; Plant inoculation ; Rhizosphere ; Shoot-to-root ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Plant growth-promoting rhizobacteria, particularly those from the genus Azospirillum spp., may affect root functions such as growth and nutrient/water uptake, which in turn may affect shoot growth. Calculations based on data from literature on shoot and root mass of crop grasses (79 plant/bacteria associations were analyzed) revealed that inoculation with Azospirillum spp. increased the shoot-to-root (S/R) ratio in about half of reported cases and decreased the S/R ratio in the other half. In 11 of 35 cases, the S/R ratio increased when the shoot mass increased more than the root mass. In 23 of 35 cases, the root mass did not increase, yet the S/R ratio still increased. Thus, the increase in the S/R ratio indicated that shoot growth responds to inoculation more than root growth. A decrease in the S/R ratio occurred when (a) root growth dominated shoot growth even though both increased (16 of 36 cases), or (b) root growth either increased or remained unchanged, and shoot growth was either unaffected or even decreased (19 of 36 cases). This analysis suggests that: (a) Azospirillum spp. participates in the partitioning of dry matter (both carbon compounds and minerals) at the whole plant level by affecting root functions, and (b) the bacteria affect crop grass through multiple mechanisms operating during plant development.
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    Gaseous nitrogen losses from fertilized soil during nitrification and denitrification using the acetylene blockage technique (1986)
    Springer
    Biology and fertility of soils 2 (1986), S. 65-70 
    Details
    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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    URL: http://dx.doi.org/10.1007/BF00257581
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    Nitrogen availability in some Wisconsin forests: comparisons of resin bags and on-site incubations (1986)
    Springer
    Biology and fertility of soils 2 (1986), S. 77-82 
    Details
    ISSN: 1432-0789
    Keywords: Ecosystem production ; Mineralization ; Nitrification ; Ion exchange resin bag method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Estimates of ammonium and nitrate availability in conifer and hardwood forests using an ion exchange resin (IER) bag method and with on-site incubations of soil cores in buried bags were compared. Correlations between the two methods were generally high. Correlation coefficients (r) between IER nitrate and buried-bag mineralized nitrate ranged from 0.87 to 0.92. Both methods also correlated well with aboveground net primary production, litter fall N content, and fine root biomass. The major differences between the methods related to the relative importances of ammonium and nitrate forms of available N. The IER method indicated that both ammonium and nitrate were important on all sites, with nitrate predominating in most soils. The buried-bag results indicated that available N was primarily in the form of nitrate (all ammonium was oxidized), but that nitrate was insignificant on infertile sites.
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    URL: http://dx.doi.org/10.1007/BF00257583
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    Volatile and water-soluble inhibitors of nitrogen mineralization and nitrification in a ponderosa pine ecosystem (1986)
    Springer
    Biology and fertility of soils 2 (1986), S. 97-104 
    Details
    ISSN: 1432-0789
    Keywords: Nitrogen mineralization ; Nitrification ; Water-soluble inhibitors ; Allelochemic control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Bioassay experiments were performed to test for inhibition of the processes of nitrogen mineralization and nitrification by organics in the forest floor of a ponderosa pine ecosystem. Water-extractable organics in the forest floor were tested by applying filtered extracts to the assay soil. The extract decreased nitrate production by 17.0% and decreased net mineralization by 4.1%. Inhibition by volatile organics was tested by placing vials containing forest floor or selected terpenoids of ponderosa pine in sealed jars containing the assay soil. Nitrate production was inhibited by 87.4% and 100%, and net nitrogen mineralization was inhibited by 73.3% and 67.7% in the jars with forest floor and terpenoids, respectively. Organics which are partially water-soluble and are volatile (such as terpenoids) would be very effective inhibitors of nitrogen cycling processes.
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    URL: http://dx.doi.org/10.1007/BF00257586
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    Effects of prescribed fire on rates of decomposition and nitrogen mineralization in a ponderosa pine ecosystem (1986)
    Springer
    Biology and fertility of soils 2 (1986), S. 87-95 
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    ISSN: 1432-0789
    Keywords: Fire effects on mineralization ; Ammonification ; Nitrification ; Ponderosa pine soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effects of a prescribed fire in a ponderosa pine ecosystem on the rates of decomposition and nitrogen mineralization (including ammonification and nitrification) in the forest floor and mineral soil horizons were evaluated. The prescribed fire immediately increased the rates of nitrogen mineralization and nitrification in the forest floor of all burned plots and in the mineral soil of one plot. The rates of decomposition, as measured by CO2 evolution, in both the forest floor and mineral soil were not significantly different immediately after the burn when expressed on an organic matter basis. The rates of nitrogen mineralization in the forest floor and mineral soil were higher 6 and 10 months after the burn. The rate of decomposition (as measured by respiration) was lower in the forest floor but not in the mineral soil 6 and 10 months after the burn. Volatile organics that may inhibit rates of nitrogen mineralization may have been consumed by prescribed fire.
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    URL: http://dx.doi.org/10.1007/BF00257585
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    Gram-positive bacterial flora on the root surface of wheat (Triticum aestivum L.) grown under different soil conditions (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 121-125 
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    ISSN: 1432-0789
    Keywords: Wheat ; Rhizosphere ; Soil Microflora ; Gram-positive Bacteria ; Coryneform Bacteria ; Arthrobacter spp. ; Mol% G+C ; Diaminopimelic acid ; DAP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We identified 108 Gram-positive bacterial strains isolated from the root surface of wheat grown under different soil conditions. The strains were divided into four groups based on morphological and physiological characteristics, but most appeared to be coryneform. The taxonomic position of the various groups was verified by the guanine+cytosine DNA contents of the strains. In general, the ranges of these values agreed with those described for the respective taxonomic positions in the literature, with a few exceptions. With soil improvement the distribution of the various groups on the root surface changed, with the coryneform group becoming dominant. This group was further divided into five subgroups, according to cell wall components, cellulose-decomposition, and morphological characteristics, and were identified to genus level. The distribution of these subgroups on the root surface of wheat did not alter with soil improvement. The genus Arthrobacter, the dominant subgroup, predominated in every plot.
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    URL: http://dx.doi.org/10.1007/BF00336051
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    Soil pH changes during legume growth and application of plant material (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 236-242 
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    ISSN: 1432-0789
    Keywords: Soil pH ; Legume ; Alkalinity ; Decarboxylation ; Ammonification ; Vicia faba L. ; Nitrification ; Zea mays L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract During cultivation of legumes soil is acidified due to proton release from roots. As a consequence of proton release, plants accumulate organic anions which may, if returned and decomposed in the soil, neutralize the soil acids. Until now the detailed processes responsible for the change in soil pH after incorporation of plant material have not been completely understood. Using a pot experiment we studied the changes in acid and base in soil during growth of field beans (Vicia faba L. cv. Alfred) and after incorporation of the plant material into the soil. Soil pH was significantly decreased by field beans from 6.00 to 5.64 in a cultivation period of 45 days. Proton release amounted to 32.7 mmol H+ pot-1, which was approximately equivalent to the accumulated alkalinity in the plant shoots (34.4 mmol). Return of field bean shoots caused a significant soil pH increase from 5.64 to 6.29. Within 7 days more than 90% of the added alkalinity was released. After 307 days incubation, soil pH decreased to 5.86 due to nitrification. In a second experiment, maize leaves (Zea mays L.), containing various concentrations of nitrogen and at various alkalinities, were incorporated into the soil. Soil pH change was positively correlated to alkalinity and malate concentration and negatively correlated to total nitrogen and water-soluble organic nitrogen of incorporated leaves. It is concluded that the soil acidification caused by legume cultivation can be partly compensated for if crop residues are returned to the soil. Addition of plant material may initially cause an increase in soil pH due to decomposition of organic anions and organic nitrogen. Soil pH may decrease if nitrification is involved. The concentrations of nitrogen and alkalinity of added plant material are decisive factors controlling soil pH change after incorporation of plant material.
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    URL: http://dx.doi.org/10.1007/BF00335950
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    N2O emissions from different cropping systems and from aerated, nitrifying and denitrifying tanks of a municipal waste water treatment plant (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 257-265 
    Details
    ISSN: 1432-0789
    Keywords: N2O release ; Cropping systems ; Waste water treatment ; Activated sludge ; Nitrification ; Demitrification ; 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 mg N2O 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 NH 4 + . 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 donorto-acceptor ratios (CH2O 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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    Soil protozoa and forest tree growth: non-nutritional effects and interaction with mycorrhizae (1995)
    Springer
    Biology and fertility of soils 20 (1995), S. 263-269 
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    ISSN: 1432-0789
    Keywords: Ectomycorrhiza ; Lactarius ; Minearl nutrition ; Picea abies ; Plant growth ; Protozoa ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Mycorrhizal (Lactarius rufus Fr.) and non-mycorrhizal Norway spruce seedlings (Picea abies Karst.) were grown in a sand culture and inoculated with protozoa (naked amoebae and flagellates) extracted from native forest soil or with protozoa grown on agar cultures. A soil suspension from which the protozoa were eliminated by filtration or chloroform fumigation was used as a control. After 19 weeks of growth in a climate chamber at 20–22°C, the seedlings were harvested. Protozoa reduced the number of bacterial colony-forming units extracted from the rhizoplane of both non-mycorrhizal and mycorrhizal seedlings and significantly increased seedling growth. However, concentrations of mineral nutrients in needles were not increased in seedlings with protozoan treatment. It is concluded that the increased growth of seedling was not caused by nutrients released during amoebal grazing on rhizosphere micro-organisms. The protozoa presumably affected plant physiological processes, either directly, via production of phytohormones, or indirectly, via modification of the structure and performance of the rhizosphere microflora and their impact on plant growth. Mycorrhizal colonization significantly increased the abundance of naked amoebae at the rhizoplane. Our observations indicate that protozoa in the rhizosphere interact significantly with mycorrhizae.
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    Plant and soil responses to mycorrhizal fungi and rhizobacteria in nodulated or nitrate-fertilized peas (Pisum sativum L.) (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 164-168 
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    ISSN: 1432-0789
    Keywords: Key wordsBacillus ; Glomus ; Mycorrhiza ; Pisum ; sativum ; Plant response ; Rhizosphere ; Root nodule ; Soil aggregation ; Soil pH ; Symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Rhizosphere organisms affect plant development and soil stability. This study was conducted to determine the effects of a vesicular-arbuscular mycorrhizal (VAM) fungus [Glomus mosseae (Nicol. &〉; Gerd.) Gerd. and Trappe] and a rhizobacterium (Bacillus sp.) on nitrate-fertilized or nodulated pea (Pisum sativum L.) plants and on the status of water-stable soil aggregates. The plants were grown in pots in a yellow clay-loam soil, and inoculated with the VAM fungus and the rhizobacterium, with one of the two, or with neither. The Bacillus sp. and G. mosseae did not affect shoot dry mass in nodulated plants. Under N fertilization, the VAM fungus enhanced plant growth, while the rhizobacterium inhibited shoot growth, VAM root colonization, and nodule formation, but enhanced the root:shoot and the seed:shoot ratios. The inhibition of shoot growth and of root colonization appeared to be related. The water stability and pH of the VAM soils were higher than those of the non-VAM soils. The rhizobacterium enhanced the water-stable aggregate status in the non-VAM soils only. Under both N-nutrition regimes, the soils had the greatest proportion of the water-stable aggregates when inoculated with both rhizo-organisms and the lowest when colonized by neither. The two rhizo-organisms affected both plants and soil, and these effects were modified by the source of N input through N2 fixation or fertilization.
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    URL: http://dx.doi.org/10.1007/s003740050225
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    Enhanced dissolution of phosphate rocks in the rhizosphere (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 169-174 
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    ISSN: 1432-0789
    Keywords: Key words Dissolution ; Open leaching ; Organic acids ; Phosphate rocks ; Plant uptake ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Dissolution of two phosphate rocks (PRS) which vary in their chemical reactivity was examined using two soils in the absence (closed-incubation and open-leaching) and presence (thin-layer) of plants. Greater dissolution was obtained in the presence than in the absence of plants. In the absence of plants, open-leaching resulted in higher dissolution than the closed-incubation system. Removal of the dissolved Ca from the zone of PR dissolution is considered to be the main reason for the increased dissolution in the open-leaching columns. In the case of the thin-layer experiment, removal of Ca and P through plant uptake and the supply of protons (H+) through the release of organic acids are considered to be the main reasons for the enhanced dissolution of PRs in the rhizosphere.
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    Influence of iron pyrites and dicyandiamide on nitrification and ammonia volatilization from urea applied to loess brown earths (luvisols) (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 179-182 
    Details
    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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    Kinetics of nitric oxide consumption in tropical soils under oxic and anoxic conditions (1997)
    Springer
    Biology and fertility of soils 25 (1997), S. 82-88 
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    ISSN: 1432-0789
    Keywords: Key words Denitrification ; Nitrification ; NO reduction ; NO oxidation ; KM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The kinetics of nitric oxide consumption in four tropical soils were studied under oxic and anoxic conditions in a flow-through system in the laboratory. Under anoxic conditions the soils had a very high affinity for NO, resulting in K M values of 0.02–0.27 ppmv NO (equivalent to 0.04–0.50 nM NO in the aqueous phase). These K M values were lower than literature values for NO consumption by denitrifying bacteria. Under oxic conditions the kinetics of NO consumption in the tropical soils were completely different, exhibiting K M values higher than 1.7 ppmv. These higher K M values were similar to literature values for NO consumption by aerobic heterotrophic bacteria. Thus, the tropical soils studied seem to contain two different NO consumption activities which can be distinguished by their kinetics and which predominate under aerobic and anaerobic conditions, respectively. However, it was not possible to quantify the contribution of each process to total NO consumption under natural conditions. Under aerobic conditions NO turnover kinetics were positively correlated with soil respiration, N mineralisation and soil organic carbon, whereas under anaerobic conditions they were positively correlated with potential and actual denitrification rates and pH.
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    Stimulation of microbial activity following spring applications of nitrogen (1997)
    Springer
    Biology and fertility of soils 26 (1997), S. 28-30 
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    ISSN: 1432-0789
    Keywords: Key words Soil microbial biomass ; Specific respiration ; Ammonification ; Nitrification ; Priming effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil microbial biomass (SMB) activity was investigated in a long-term experiment in which grazed swards received annual inputs of 200 N kg ha–1. SMB total C and total N, specific respiration, ammonification and nitrification were examined over a 10 week period, following the first and the second seasonal applications of N. Whilst there was no effect on biomass C and N, additions of N appeared to increase biomass activity. Nitrification was weakly correlated with ammonification (r 2=0.413) and the latter was stimulated by the addition of N (P〈0.05), suggesting a ‘priming’ effect.
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    Concurrent measurements of net mineralization, nitrification, denitrification and leaching from field incubated soil cores (1998)
    Springer
    Biology and fertility of soils 26 (1998), S. 323-330 
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    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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    Kinetic properties and stability of potato acid phosphatase immobilized on Ca-polygalacturonate (1998)
    Springer
    Biology and fertility of soils 27 (1998), S. 97-103 
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    ISSN: 1432-0789
    Keywords: Key words Potato acid phosphatase ; Ca-Polygalacturonate ; Rhizosphere ; Mucigel ; Michaelis-Menten kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Acid phosphatase from potato was adsorbed and immobilized on a pre-formed network of Ca-polygalacturonate, a substrate which has a composition and morphology similar to the mucigel present at the root-soil interface. The influence of different types of organic buffers on enzyme adsorption and activity was investigated. The highest enzyme activity, for free and adsorbed enzyme, was obtained with Na-maleate buffer at pH 6.0, which was used for all subsequent experiments. The Michaelis-Menten kinetic parameters, Vmax and Km, were determined for free and adsorbed phosphatase. Vmax showed a 60% decrease upon adsorption (2.09±0.30 U/mg, for the soluble form and 0.84±0.15 U/mg, for the adsorbed enzyme), whereas Km increased from 0.49±0.15 mM for the free enzyme to 0.99±0.20 mM for adsorbed phosphatase. Phosphatase adsorption decreased as the concentration of NaCl increased, indicating that the enzyme is bound to the carrier gel through coulombic interactions. Adsorption increased stability of the enzyme as compared with the free enzyme (t 1/2 of the activity was 9.4 days and 5.8 days, respectively), but increased thermal and proteolytic inactivation. The pH/activity profile revealed no change in terms of shape or optimum pH (4.5) upon adsorption of the enzyme. These results indicate that adsorption of acid phosphatase on Ca-polygalacturonate induces changes in the kinetic properties and stability of the enzyme, and the same type of response can be extrapolated from these results for acid phosphatases of the rhizosphere.
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    Mechanisms of N2O and NO production in the soil profile of a drained and forested peatland, as studied with acetylene, nitrapyrin and dimethyl ether (1998)
    Springer
    Biology and fertility of soils 27 (1998), S. 205-210 
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    ISSN: 1432-0789
    Keywords: Key words Nitrous oxide ; Nitric oxide ; Organic soil ; Nitrification ; Inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Acetylene, dimethyl ether (DME) and 2-chloro-6-trichloromethyl pyridine (nitrapyrin) were used as inhibitors to study the contributions of nitrification and denitrification to the production of N2O and nitric oxide (NO) in samples taken from the soil profile of a peatland drained for forestry. Acetylene and DME inhibited 60–100% of the nitrification activity in field-moist samples from the 0–5 cm and 5–10 cm peat layers, whereas nitrapyrin had no inhibitory effect. In the 0–5 cm peat layer the N2O production could be reduced by up to 90% with inhibitors of nitrification, but in the 5–10 cm peat layer this proportion was 20–30%. All the inhibitors removed 96–100% of the nitrification potential in peat-water slurries from the 0–5 cm peat layer, but the 5–10 cm layer had a much lower nitrification activity, and here the efficiency of the inhibitors was more variable. Litter was the main net source of NO in the peat profile. NO3 – production was lower in the litter layer than in the peat, whereas N2O production was much higher in the litter than in the peat. Denitrification was the most probable source of N2O and NO in the litter, which had a high availability of organic substrates.
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    The number of bacteria in the rhizosphere during plant development: relating colony-forming units to different reference units (1999)
    Springer
    Biology and fertility of soils 28 (1999), S. 285-291 
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    ISSN: 1432-0789
    Keywords: Key words Chrysanthemum ; Rhizosphere ; Rhizobacteria ; Root age ; Reference unit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The number of bacteria was determined during the growth of chrysanthemum plants on young (tip) and old (base) root parts. We assessed if the same conclusions could be drawn on the dynamics of bacterial populations during plant development when different reference units were used to express the bacterial counts. The results indicated that the total number of bacteria on the base decreased significantly during plant development, when expressed per root length, per root fresh weight or per root surface. The number of bacteria on the tip only decreased significantly when expressed per root length. Using the unit of dry weight of adhering soil, contradictory results were obtained for both base and tip; in general, the number of bacteria increased significantly during plant development. Thus, different reference units may lead to different conclusions. Root surface seemed to be the best unit to use, but the use of this unit requires time-consuming measurements. Regression analyses indicated that the reference unit "root surface" was highly correlated with root fresh weight (R 2=93%). Thus, once this relation is determined, the less time-consuming unit can be measured in the experimental work. To analyse the data, the colony-forming units should be expressed per root surface. Besides bacterial numbers during plant development, we assessed whether the bacterial populations collected showed different growth rates on agar plates. The growth rates of bacteria from the tip and base and different development stages of the plants showed differences, indicating differences in the metabolic state of the collected populations.
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    Solubilization of inorganic phosphates and growth emergence of wheat as affected by Azotobacter chroococcum mutants (1999)
    Springer
    Biology and fertility of soils 28 (1999), S. 301-305 
    Details
    ISSN: 1432-0789
    Keywords: Key words Azotobacter chroococcum ; Inorganic phosphate solubilization ; Indole acetic acid ; Growth emergence ; Wheat ; Phytohormone production ; Rhizosphere ; Phosphate solubilizing bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Phosphate-solubilizing strains of A. chroococcum isolated from the wheat rhizosphere were evaluated for their ability to solubilize tricalcium phosphate (TCP), Mussoorie rock phosphate (MRP) and also for indole-acetic-acid (IAA) production. Strains were selected on the basis of the clearance zone on solid agar media of Pikovskaya and Jensen's media containing TCP, and phosphate solubilization in Jensen's liquid culture medium containing both TCP and MRP. Mutants of the best phosphate-solubilizing (TCP 1.52 μg ml–1 MRP 0.19 μg ml–1), IAA-producing A. chroococum strain P-4, were developed and screened for P solubilization and phytohormone production. Five mutants solubilized more P (in the range of 1.5–1.7 μg/ml–1 of TCP and 0.19–0.22 μg ml–1 of MRP) than the parent strains. In vitro growth emergence studies of three wheat varieties, viz. C-306, WH-542 and HD-2009, showed better performance with phosphate-solubilizing mutants than with the parent strain.
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    URL: http://dx.doi.org/10.1007/s003740050497
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    Phosphate-solubilizing microorganisms associated with the rhizosphere of mangroves in a semiarid coastal lagoon (2000)
    Springer
    Biology and fertility of soils 30 (2000), S. 460-468 
    Details
    ISSN: 1432-0789
    Keywords: Key words Mangrove ; Bacillus spp. ; Enterobacter spp. ; Inorganic phosphate-solubilizing microorganisms ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The phosphate-solubilizing potential of the rhizosphere microbial community in mangroves was demonstrated when culture media supplemented with insoluble, tribasic calcium phosphate, and incubated with roots of black (Avicennia germinans L.) and white [Laguncularia racemosa (L.) Gaertn.] mangrove became transparent after a few days of incubation. Thirteen phosphate-solubilizing bacterial strains were isolated from the rhizosphere of both species of mangroves: Bacillus amyloliquefaciens, Bacillus licheniformis, Bacillus atrophaeus, Paenibacillus macerans, Vibrio proteolyticus, Xanthobacter agilis, Enterobacter aerogenes, Enterobacter taylorae, Enterobacter asburiae, Kluyvera cryocrescens, Pseudomonas stutzeri, and Chryseomonas luteola. One bacterial isolate could not be identified. The rhizosphere of black mangroves also yielded the fungus Aspergillus niger. The phosphate-solubilizing activity of the isolates was first qualitatively evaluated by the formation of halos (clear zones) around the colonies growing on solid medium containing tribasic calcium phosphate as a sole phosphorus source. Spectrophotometric quantification of phosphate solubilization showed that all bacterial species and A. niger solubilized insoluble phosphate well in a liquid medium, and that V. proteolyticus was the most active solubilizing species among the bacteria. Gas chromatographic analyses of cell-free spent culture medium from the various bacteria demonstrated the presence of 11 identified, and several unidentified, volatile and nonvolatile organic acids. Those most commonly produced by different species were lactic, succinic, isovaleric, isobutyric, and acetic acids. Most of the bacterial species produced more than one organic acid whereas A. niger produced only succinic acid. We propose the production of organic acids by these mangrove rhizosphere microorganisms as a possible mechanism involved in the solubilization of insoluble calcium phosphate.
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    Release and consumption of nitrogen by snail feces in Negev Desert soils (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 399-404 
    Details
    ISSN: 1432-0789
    Keywords: Key words Snails ; Nitrogen ; Desert ; Mineralization ; Nitrification ; Respiration ; Feces ; N cycling processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Snail grazing and feces production have been shown to be major components of the nitrogen (N) budget of Negev Desert ecosystems. However, the movement of N from feces into soil N cycling processes has not been studied. In this study, we measured immediate N release from different types of snail feces following wetting of dry desert soils, and characterized potential net N mineralization and nitrification and soil respiration over a 12-day incubation under laboratory conditions. The dynamics of inorganic N exhibited two distinct phases during the 12-day incubation: (1) immediate release of inorganic N following wetting of the soil and (2) decline of inorganic N from day 1 to day 12 of the incubation. The immediate pulse of N release from this one wetting event (6–25 mg N m–2) was larger than annual atmospheric inputs of N to Negev Desert ecosystems (〈2 mg N m–2); however, from 50 to 80% of the N released upon wetting was consumed by the end of the incubation. There were differences in inorganic N release and respiration from feces from different kinds of snails, and from feces from the same species of snail fed different plants. The results suggest that while snail feces contribute significant amounts of plant available N to Negev ecosystems, plants must compete with other “sinks” for this N.
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    Release and consumption of nitrogen by snail feces in Negev Desert soils (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 399-404 
    Details
    ISSN: 1432-0789
    Keywords: Snails ; Nitrogen ; Desert ; Mineralization ; Nitrification ; Respiration ; Feces ; N cycling processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Snail grazing and feces production have been shown to be major components of the nitrogen (N) budget of Negev Desert ecosystems. However, the movement of N from feces into soil N cycling processes has not been studied. In this study, we measured immediate N release from different types of snail feces following wetting of dry desert soils, and characterized potential net N mineralization and nitrification and soil respiration over a 12-day incubation under laboratory conditions. The dynamics of morganic N exhibited two distinct phases during the 12-day incubation: (1) immediate release of inorganic N following wetting of the soil and (2) decline of inorganic N from day 1 today 12 of the incubation. The immediate pulse of N release from this one wetting event (6–25 mg N m-2) was larger than annual atmospheric inputs of N to Negev Desert ecosystems (〈2 mg N m-2); however, from 50 to 80% of the N released upon wetting was consumed by the end of the incubation. There were differences in inorganic N release and respiration from feces from different kinds of snails, and from feces from the same species of snail fed different plants. The results suggest that while snail feces contribute significant amounts of plant available N to Negev ecosystems, plants must compete with other “sinks” for this N.
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    Azospirillum spp. participation in dry matter partitioning in grasses at the whole plant level (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 435-440 
    Details
    ISSN: 1432-0789
    Keywords: Azospirillum spp. ; Crop plants ; Plant growth-promoting rhizobacteria ; Plant inoculation ; Rhizosphere ; Shoot-to-root ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Plant growth-promoting rhizobacteria, particularly those from the genus Azospirillum spp., may affect root functions such as growth and nutrient/water uptake, which in turn may affect shoot growth. Calculations based on data from literature on shoot and root mass of crop grasses (79 plant/bacteria associations were analyzed) revealed that inoculation with Azospirillum spp. increased the shoot-to-root (S/R) ratio in about half of reported cases and decreased the S/R ratio in the other half. In 11 of 35 cases, the S/R ratio increased when the shoot mass increased more than the root mass. In 23 of 35 cases, the root mass did not increase, yet the S/R ratio still increased. Thus, the increase in the S/R ratio indicated that shoot growth responds to inoculation more than root growth. A decrease in the S/R ratio occurred when (a) root growth dominated shoot growth even though both increased (16 of 36 cases), or (b) root growth either increased or remained unchanged, and shoot growth was either unaffected or even decreased (19 of 36 cases). This analysis suggests that: (a) Azospirillum spp. participates in the partitioning of dry matter (both carbon compounds and minerals) at the whole plant level by affecting root functions, and (b) the bacteria affect crop grass through multiple mechanisms operating during plant development.
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    URL: http://dx.doi.org/10.1007/BF00335919
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    Nitrogen fertilizers promote denitrification (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 211-220 
    Details
    ISSN: 1432-0789
    Keywords: Key words Denitrification ; Fertilizer efficiency ; 15N ; Labelled dinitrogen ; Nitrification ; Nitrous oxide ; Urea ; Waterlogged soil ; Water-soluble organic carbon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A laboratory study was conducted to compare the effects of different N fertilizers on emission of N2 and N2O during denitrification of NO3 – in waterlogged soil. Field-moist samples of Drummer silty clay loam soil (fine-silty, mixed, mesic Typic Haplaquoll) were incubated under aerobic conditions for 0, 2, 4, 7, 14, 21, or 42 days with or without addition of unlabelled (NH4)2SO4, urea, NH4H2PO4, (NH4)2HPO4, NH4NO3 (200 or 1000 mg N kg–1 soil), or liquid anhydrous NH3 (1000 mg N kg–1 soil). The incubated soil samples were then treated with 15N-labelled KNO3 (250 mg N kg–1 soil, 73.7 atom% 15N), and incubation was carried out under waterlogged conditions for 5 days, followed by collection of atmospheric samples for 15N analyses to determine labelled N2 and N2O. Compared to samples incubated without addition of unlabelled N, all of the fertilizers promoted denitrification of 15NO3 –. Emission of labelled N2 and N2O decreased in the order: Anhydrous NH3〉urea〈$〉\gg〈$〉 (NH4)2HPO4〉(NH4)2SO4≃NH4NO3≃NH4H2PO4. The highest emissions observed with anhydrous NH3 or urea coincided with the presence of NO2 –, and 15N analyses indicated that these emissions originated from NO2 – rather than NO3 –. Emissions of labelled N2 and N2O were significantly correlated with fertilizer effects on soil pH and water-soluble organic C.
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    URL: http://dx.doi.org/10.1007/s003740050233
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    Carbon and nitrogen mineralization in subarctic agricultural and forest soils (1988)
    Springer
    Biology and fertility of soils 6 (1988), S. 33-38 
    Details
    ISSN: 1432-0789
    Keywords: Microbial activity ; Nitrification ; Taiga ; Tillage system ; Crop residue management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary C and N mineralization potentials were determined, in a 12-week laboratory incubation study, on soil samples obtained from recently cleared land which had been cropped to barley for 4 years (field soils) and from nearby undisturbed taiga (forest soils). Treatments for the cropped soils were conventional and no-tillage with and without crop residues removed. An average of about 3% of the total C was evolved as CO2 from the field soils compared with 〉 10% and 4% for the upper (Oie) and lower (Oa) forest-floor horizons, respectively. Significantly more C was mineralized from the Ap of the no-till treatment with residue left on the surface than from the other field Ap horizons. Both forest-floor horizons showed rather long lag periods for net mineralization compared with the field soils, but at the end of the incubation, more mineral N was recovered from the forest Oie despite a rather wide C:N ratio, than from the field soils. After 12 weeks about 115, 200 and 20 μg mineral N/g soil were recovered from the field Ap, the forest Oie and the forest Oa horizons, respectively. Very little C or N was mineralized from the B horizon of the forest or the field soils. Nitrification was rapid and virtually complete for the field soils but was negligible for both forest-floor O horizons.
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    URL: http://dx.doi.org/10.1007/BF00257917
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    Methane-oxidizing activities and methanotrophic populations associated with wetland rice plants (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 261-265 
    Details
    ISSN: 1432-0789
    Keywords: Key words Methane ; Wetland rice soils ; Oryza sativa ; Methane oxidation ; Acetylene Propylene oxide ; Methanotrophs ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Acetylene up to 500 μl l–1 did not affect methane formation in anoxic soil up to 12 h, but further incubation for 1 week showed strong inhibition of methanogenesis. To ascertain the extent of the oxidation of methane produced from rice-planted pots, the effect of acetylene on methane emission was studied. Two rice varieties (Toyohatamochi and Yamahikari) were grown in a greenhouse in submerged soil in pots. At about maximum tillering, heading, and grain-forming stages, methane fluxes were measured. Flux measurement was performed for 3 h from 6 pm, then acetylene at 100 μl l–1 was added to some of the pots. At 6 a.m. the following day, methane fluxes were again measured for 3 h. Only at maximum tillering stage of the variety Toyohatamochi was a significant increase (1.4 times) in methane flux caused by acetylene observed, whereas in the other treatments no significant increase in methane fluxes by acetylene could be defected. To ascertain the activity of methane monooxygenase (MMO), propylene oxide (PPO) formation from propylene was measured with excised roots and a basal portion of stems of the rice plants grown on the submerged soil. A level of 0.1–0.2 μmol PPO h–1 plant–1 was recorded. The roots showed the highest PPO formation per gram dry matter, followed by basal stems. Methane oxidation was roughly proportional to PPO formation. Soluble MMO-positive methanotroph populations were measured by plate counts. The number of colony-forming units per gram dry matter was 106–105 in roots, and 104–103 in basal stems. These results indicate the possibility of methane oxidation in association with wetland rice plants.
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    URL: http://dx.doi.org/10.1007/s003740050241
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    Using the spermosphere model technique to describe the dominant nitrogen-fixing microflora associated with wetland rice in two Egyptian soils (1989)
    Springer
    Biology and fertility of soils 7 (1989), S. 158-163 
    Details
    ISSN: 1432-0789
    Keywords: Rhizosphere ; N2-fixation ; Wetland rice ; Dominant microflora ; Spermosphere model ; Enterobacter cloacae ; Enterobacter agglomerans ; Citrobacter freundii ; Klebsiella planticola ; Azospirillum lipoferum ; Azospirillum brasilense
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary This study is an attempt to describe the dominant N2-fixing microflora associated with the roots of wetland rice. Rice cultivar Giza 171 was grown in a phytotron on two alluvial Egyptian soils for 8 days, a stage when the nitrogenase activity of undisturbed plants reached a level of 245 × 10−6 mol C2H4 h−1 g−1 dry weight of leaf. The roots and rhizosphere soils were then used for counting and isolating dominant diazotrophs. Counts and initial enrichment steps were carried out on a selective medium made of an axenic rice plantlet, the “spermosphere model”, incubated under 1 % acetylene. The counts were very high, exceeding 108 bacteria g−1 dry weight of rhizosphere soil. Enterobacteriaceae were dominant; most isolates were Enterobacter cloacae belonging to different biotypes in the two soils. Enterobacter agglomerans, Citrobacter freundii and Klebsiella planticola were also present as members of the dominant microflora. Azospirillum brasilense and Azospirillum lipoferum were present as well, but less abundant.
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    N2O emissions from different cropping systems and from aerated, nitrifying and denitrifying tanks of a municipal waste water treatment plant (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 257-265 
    Details
    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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    Nitrification of ammonium in different components of a flooded rice soil system (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 321-326 
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    ISSN: 1432-0789
    Keywords: Key words Nitrification ; Flooded rice soils ; Rhizosphere ; Rice variety ; Crop growth stage ; Organic amendment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nitrification associated with the various components [subsurface soil from unplanted and planted (rhizosphere) fields, standing water and surface soil from planted and unplanted fields and leaf sheath suspensions] of submerged rice paddies was examined in incubation experiments with solutions inoculated with soil or water samples. Substantial nitrification occurred in all samples, standing water and surface soil samples in particular, during their 40-day incubation with NH4 +-N. Almost all the NH4 +-N, disappeared during incubation with standing water, was recovered as NO3 –-N. This, compared to 70–80% from all soil samples and only 29% from leaf sheath suspensions. Significant loss of nitrogen, especially from leaf sheath suspensions, is probably due to nitrification-denitrification as evidenced by its complete recovery in the presence of N-Serve. Nitrification potential of the soil and water samples varied with the crop growth stage and was more pronounced at tillering and panicle inititation stages than at other stages. Nitrification potential of samples from green-manure-amended plots was distinctly less than that of samples from control and urea-amended plots. Most probable number (MPN) estimates of ammonium-oxidizing bacteria were always higher in surface soil in both planted and unplanted plots at all stages of crop growth.
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    Gram-negative bacterial flora on the root surface of wheat (Triticum aestivum) grown under different soil conditions (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 273-281 
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    ISSN: 1432-0789
    Keywords: Wheat ; Triticum aestivum ; Rhizosphere ; Soil microflora ; Gram-negative bacteria ; API 20 NE ; Flavobacterium spp ; Cytophaga
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We identified 161 Gram-negative bacterial strains isolated from the root surface of wheat grown under different soil conditions. The strains were divided into seven groups based on major morphological and physiological properties. Taxonomic allocation of the groups was verified by guanine+cytosine contents of DNA. Except for one group, which may be assumed to include bacteria belonging to the genera Flavobacterium and Cytophaga, the various groups were taxonomically united. The distribution of the groups changed with soil improvement. Pseudomonads predominated in unimproved soil, but Flavobacterium and Cytophaga spp. were predominant in the most improved soil. As all the strains were non-fermentative by Hugh and Leifson's test, API 20NE identification was applied. However, many strains were misidentified by this system, especially in the Flavobacterium and Cytophaga spp. group. For ecological studies, the strains were classified to species level by the API 20 NE system and by the results of a combination of guanine+cytosine (mol%) and isoprenoid quinone data. The pattern of distribution of the bacteria on the root surface of wheat varied at species level within one genus depending on soil conditions.
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    Movement of urea and its hydrolysis products as influenced by moisture content and urease inhibitors (1996)
    Springer
    Biology and fertility of soils 22 (1996), S. 101-108 
    Details
    ISSN: 1432-0789
    Keywords: Key words Urea ; Urease inhibitors ; Hydroquinone ; Phenylphosphorodiamidate ; N-(n-butyl)phosphorothioic triamide ; Nitrification ; Nitrogen movement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A laboratory experiment was conducted on an Aquic Udifluvent Belgian soil in order to study the movement of urea and its hydrolysis products. This study was carried out at two moisture levels (10 and 20%) upon the addition of three types of urease inhibitors: hydroquinone, phenylphosphorodiamidate (PPDA), and N-(n-butyl)phos- phorothioic triamide (NBPT). The results clearly show the effects of the inhibitors in retarding the hydrolysis of urea. The highest effect was observed with NBPT, followed by hydroquinone, and PPDA. The effect was more pronounced at 10% than at 20% moisture content. It was clear that subsequent nitrification of the NH4 + formed was inhibited at the lower moisture level. At 10% moisture, from the 7th day of incubation on, some NH4 + moved about 3 cm and reached the top of the soil column. At 20% moisture, no NH4 + reached the surface as it was quickly nitrified. After 17 days of incubation and at 20% moisture, the total mineral N was more or less homogeneously distributed within the soil column. In contrast, at 10% moisture, the remaining urea and the hydrolysis products were still concentrated at the place of application. The distribution of urea and its hydrolysis products was comparable with 7 days of incubation at 20% moisture and 17 days at 10%.
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    Mineralization of carbon and nitrogen, and nitrification in Scots pine forest soil treated with fast- and slow-release nitrogen fertilizers (1996)
    Springer
    Biology and fertility of soils 22 (1996), S. 214-220 
    Details
    ISSN: 1432-0789
    Keywords: Dicyandiamide ; Forest soil ; Mineralization ; Nitrification ; Urea ; Urea-formaldehyde
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We studied the effects of fast- and slow-release organic N fertilizers (urea and urea-formaldehyde, Nitroform) on mineralization, nitrification, and N leaching in an acid, poor forest soil. We also studied the effects of a nitrification inhibitor (dicyandiamide) applied together with urea. Net nitrification, mineralization of N and C were determined by aerobic laboratory incubation of soil samples taken one and three growing seasons after N application. Numbers of autotrophic nitrifiers were estimated by a most probable number method three growing seasons after the treatment. Urea increased the CO2 production immediately after application, but after three growing seasons, CO2 production was the lowest in the urea-treated soils. In the nitroform-treated soils, the concentration of exchangeable NH inf4 sup+ after the first and third growing seasons was of the same magnitude, in contrast to the urea-treated soils, where hydrolysis took place immediately. Three growing seasons after application, the highest amount of NH inf4 sup+ accumulated during the laboratory incubation was in the nitro-form-treated soils. Unlike urea, nitroform did not increase the production of NO inf3 sup- or the number of NH inf4 sup+ oxidizers. In the urea+dicyandiamide-treated soils there was less NO inf3 sup- and a lower number of nitrifiers than in the urea-treated soils. The results showed that a slow-release N fertilizer, such as nitroform, increases the availability of mineral N in acid forest soils without increasing nitrification and hence the risk of NO inf3 sup- leaching.
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    URL: http://dx.doi.org/10.1007/BF00382515
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    Effects of rate and depth of fertilizer application on emission of nitrous oxide from soil fertilized with anhydrous ammonia (1986)
    Springer
    Biology and fertility of soils 2 (1986), S. 201-204 
    Details
    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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    URL: http://dx.doi.org/10.1007/BF00260844
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    Effects of various nitrogen fertilizers on emission of nitrous oxide from soils (1986)
    Springer
    Biology and fertility of soils 2 (1986), S. 195-199 
    Details
    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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    URL: http://dx.doi.org/10.1007/BF00260843
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    Effects of ammonium and nitrate on mineralization of nitrogen from leguminous residues (1995)
    Springer
    Biology and fertility of soils 20 (1995), S. 49-52 
    Details
    ISSN: 1432-0789
    Keywords: Nitrification ; N immobilization ; N mineralization ; N interaction ; N-Serve ; Nitrapyrin ; Soil N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A laboratory incubation experiment was conducted to compare the effects of NH inf4 sup+ and NO inf3 sup- on mineralization of N from 15N-labelled vetch (Vicia villosa Rotn) in an Illinois Mollisol, and to determine the effect of a nitrification inhibitor (nitrapyrin) on mineralization of vetch N when used with NH inf4 sup+ . The addition of either NH inf4 sup+ or NO inf3 sup- (100 and 200 mg N kg-1 soil) significantly increased mineralization of vetch N during incubation for 40 days. The effect was greater with NH inf4 sup+ than with NO inf3 sup- , and a further increase occurred in the presence of nitrapyrin (10 mg kg-1 soil). The addition of NO inf3 sup- retarded the nitrification of NH inf4 sup+ -N derived from vetch.
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    URL: http://dx.doi.org/10.1007/BF00307840
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    Growth and nitrogen nutrition of maize (Zea mays L.) in soil treated with the nitrification-inhibiting insecticide Baythroid (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 161-165 
    Details
    ISSN: 1432-0789
    Keywords: ANI ; Baythroid ; Cyfluthrin ; Insecticide ; 15N ; Nitrification ; N uptake ; Synthetic pyrethroid ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A pot experiment was conducted to compare the uptake and dry matter production potential of NH inf4 sup+ and NO inf3 sup- and to study the effect of Baythroid, a contact poison for several insect pests of agricultural crops, on growth and N uptake of maize (Zea mays L.). Nitrogen was applied as (15NH4)2SO4, K15NO3, or 15NH4NO3 and in one treatment Baythroid was combined with 15NH4NO3. Source of N had, in general, a nonsignificant effect on dry matter and N yield, but uptake of NO inf3 sup- was significantly higher than that of NH inf4 sup+ when both N sources were applied together. Substantial loss of N occurred from both the sources, with NH inf4 sup+ showing greater losses. Baythroid was found to have a significant positive effect on dry matter yield of both root and shoot; N yield also increased significantly. Uptake of N from both the applied and native sources increased significantly in the presence of Baythroid and a substantial added nitrogen interaction (ANI) was determined. The positive effect of Baythroid was attributed to: (1) a prolonged availability of NH inf4 sup+ due to inhibition of nitrification, (2) an increased availability of native soil N through enhanced mineralization, and (3) an enhanced root proliferation.
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    Antagonistic effect of Pseudomonas spp. on pathogenic fungi and enhancement of growth of green gram (Vigna radiata) (1999)
    Springer
    Biology and fertility of soils 29 (1999), S. 62-68 
    Details
    ISSN: 1432-0789
    Keywords: Key words Pseudomonas spp. ; Vigna radiata ; Rhizosphere ; Antifungal activity ; Dinitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Pseudomonas species were isolated from the rhizosphere of green gram [Vigna radiata (L.) Wilczek] and some of the rhizobacterial isolates were found to have a wide range of antifungal activity inhibiting growth of the phytopathogenic fungi Aspergillus sp., Curvularia sp., Fusarium oxysporum and Rhizoctonia solani in culture. These isolates also showed slight inhibition of the growth of a Bradyrhizobium strain (Vigna) in a spot test which was mainly a result of nutrient competition as culture supernatants of the Pseudomonas isolates did not inhibit the growth of bradyrhizobia but inhibited the growth of fungi. The rhizobacterial isolates produced siderophores in Fe-deficient succinate medium. However, the inhibition of fungal growth by different Pseudomonas isolates in Luria Bertani and King's medium B which were not limiting in Fe3+ ions suggested that, besides siderophores, other antifungal compounds (antibiotics) produced by these rhizobacteria were involved in antagonism. On coinoculation of green gram with Pseudomonas strains MRS13 and MRS16 and Bradyrhizobium sp. (Vigna) strain S24, there was a significant increase in nodule weight, plant dry weight and total plant N as compared to inoculation with Bradyrhizobium strain S24 alone, suggesting that the nodule-promoting effects of Pseudomonas sp. lead to an increase in symbiotic N fixation and plant growth.
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    URL: http://dx.doi.org/10.1007/s003740050525
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    Effect of low pO2 on colonization of maize roots by a genetically altered Pseudomonas putida [PH6(L1019)] (1997)
    Springer
    Biology and fertility of soils 26 (1997), S. 43-49 
    Details
    ISSN: 1432-0789
    Keywords: Key words Low pO2 ; Rhizosphere ; Pseudomonads ; Competition ; LacZY
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Among the factors which may affect colonization of roots by soil bacteria is that of rhizosphere oxygen partial pressure (pO2). The oxygen concentration in the root zone influences both microbes and roots. Roots exposed to low pO2, as might occur during flooding and waterlogging of the soil, become more leaky and loss of soluble carbon increases. To determine whether periods of low pO2 increased root colonization by a genetically altered pseudomonad we inoculated 3- to 4-week-old maize plants, grown in soil and transferred to a hydroponic system or grown in fritted clay, with Pseudomonas putida PH6(L1019)(lacZY+) following exposure of the roots to air or cylinder N2. Numbers of heterotrophs and the marked pseudomonad were determined by dilution plating. Low pO2 generally increased the numbers of bacteria associated with roots exposed to the treatments in solution or in undisturbed fritted clay rooting medium. Under low pO2 in a hydroponic system, roots of intact maize plants tended also to have higher soluble organic C and hexose (anthrone-detectable sugars) than roots exposed to air. The effect of low pO2 was most pronounced in the fritted clay where low pO2 favored colonization by the marked strain; numbers were 3- to 96-fold greater than those on roots flushed with air but accounted for only 0.06–0.61% of the total population. Roots exposed to low pO2 tended to accumulate more C. Results suggest that in the fritted clay, the pseudomonad was able to exploit the increased C supply and to achieve greater numbers on roots exposed to low pO2, whereas the dilution of carbon released from roots in the hydroponic apparatus did not allow for the same magnitude of increase on roots.
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    URL: http://dx.doi.org/10.1007/s003740050341
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    Effects of marigold (Tagetes sp.) roots on soil microorganisms (1998)
    Springer
    Biology and fertility of soils 27 (1998), S. 149-154 
    Details
    ISSN: 1432-0789
    Keywords: Key words Marigold ; Tagetes ; Rhizosphere ; Nematode suppression ; Bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Marigolds (genus Tagetes) suppress populations of soil endopathogenic nematodes such as Pratylenchus penetrans and Meloidogyne species. Nematode suppression by marigolds is thought to be due to thiophenes, heterocyclic sulfur-containing molecules abundant in this plant. When activated, thiophenes such as α-terthienyl produce oxygen radicals. If marigold roots release such a powerful biocidal agent and it is activated in soil, microbial populations in the marigold rhizosphere should be substantially perturbed. We made various measurements of microbial population size and activity in soils that had been cropped to marigolds (Crackerjack, Creole) in the field and in the greenhouse, and compared these with bare soil and soil cropped to rye (Secale cereale L.). Total extractable microbial biomass (measured by the fumigation extraction method), total bacteria (measured by epifluorescence microscopy on 5-(4,6-dichlorotriazine-2-γl) aminofluorescein-stained preparations), heterotrophic bacteria (measured by plate count on various media), and nitrite-oxidizing bacteria (measured by the most-probable-number method) were not significantly different in any of the treatments. Residues of 14C-labelled rye were mineralized slightly more rapidly in rye-cropped soil than in the other treatments, which were comparable. The rates of die-back of introduced cells of the bacteria Escherichia coli and Rhodococcus TE1 were similar in marigold-cropped and control soils, suggesting that there was not a noteworthy accumulation of biocidal agents in soils cropped to marigolds. We conclude that marigolds do not cause a general depression in the numbers of microorganisms in soils, and that nematode control by this plant may not be due to the release of a biocidal agent into the soil.
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    URL: http://dx.doi.org/10.1007/s003740050413
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    Combining field incubation with nitrogen-15 labelling to examine nitrogen transformations in low to high intensity grassland management systems (2000)
    Springer
    Biology and fertility of soils 30 (2000), S. 492-499 
    Details
    ISSN: 1432-0789
    Keywords: Key words Nitrogen-15 mean pool dilution ; Mineralization ; Immobilization ; Nitrification ; Field incubation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The 15N isotope dilution method was combined with a field incubation technique to provide simultaneous measurements of gross and net rates of N turnover in three long-term swards: unfertilized (Z) or receiving N either from N fixation as clover (C), or as 200 kg fertilizer N ha–1 year–1 (F). Uniform N enrichment of soil microplots was achieved with a multi-point soil injector to measure mineralization/immobilization turnover and nitrification over a 4-day incubation. Net rates of mineralization ranged between 0.6 and 2.9 μg N g–1 day–1 and in all three treatments were approximately half the gross rates. Nitrification rates (gross) were between 1.0 and 1.6 μg N g–1 day–1. In the F treatment, the turnover of NH4 +-N and NO3 –-N pools was on a 2- and 4-day cycle, respectively, whereas in the N-limited treatments (C and Z) turnover rates were faster, with the NO3 –-N pools turning over twice as fast as the NH4 +-N pools. Therefore, available N was recycled more efficiently in the C and Z treatments, whereas in the F treatment a higher N pool size was maintained which would be more vulnerable to leakage. A large proportion of the added 15N was recovered in the soil microbial biomass (SMB), which represented a 4–5 times larger sink for N than the plant biomass. Although the C treatment had a significantly lower SMB than the grass-only treatments, there were no differences in microbial activity. Gross rates of nitrification increased along the gradient of N input intensity (i.e. Z〈C〈F), and the addition of a nitrification inhibitor (C2H2) tended to increase microbial immobilization, but did not influence plant N uptake. In this study, the value of combining different techniques to verify net rates was demonstrated and the improved methodology for 15N labelling of soil enabled measurements to be obtained from relatively undisturbed soil under natural field conditions.
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    URL: http://dx.doi.org/10.1007/s003740050028
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    Survival and cell culturability of biocontrol Pseudomonas fluorescens CHA0 in the rhizosphere of cucumber grown in two soils of contrasting fertility status (2000)
    Springer
    Biology and fertility of soils 32 (2000), S. 217-221 
    Details
    ISSN: 1432-0789
    Keywords: Key words  Pseudomonas fluorescens ; Cucumber ; Rhizosphere ; Biocontrol ; Culturability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The effect of cucumber roots on survival patterns of the biocontrol soil inoculant Pseudomonas fluorescens CHA0-Rif was assessed for 22 days in two non-sterile soils, using a combination of total immunofluorescence cell counts, Kogure's direct viable counts and colony counts on plates containing rifampicin. In Eschikon soil (high fertility status for cucumber), CHA0-Rif persisted as culturable cells in bulk soil and in the rhizosphere, but colony counts were lower than viable counts and total cell counts inside root tissues. The occurrence of viable but non-culturable (VBNC) cells inside root tissues (5 log cells g–1 root) was unlikely to have resulted from the hydrogen peroxide treatment used to disinfect the root surface, as hydrogen peroxide caused the death of CHA0-Rif cells in vitro. In Siglistorf soil (low fertility status for cucumber), the inoculant was found mostly as non-culturable cells. Colony counts and viable counts of CHA0-Rif were similar, both in bulk soil and inside root tissues, whereas in the rhizosphere viable counts exceeded colony counts at the last two samplings (giving about 7 log VBNC cells g–1). In conclusion, soil type had a significant influence on the occurrence of VBNC cells of CHA0-Rif, although these cells were found in root-associated habitats (i.e. rhizosphere and root tissues) and not in bulk soil.
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    Misidentification of soil bacteria by fatty acid methyl ester (FAME) and BIOLOG analyses (2000)
    Springer
    Biology and fertility of soils 32 (2000), S. 256-258 
    Details
    ISSN: 1432-0789
    Keywords: Key words Arthrobacter ; Micrococcus ; Rhizosphere ; Similarity index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Fatty acid methyl ester (FAME) analysis is commonly used by soil scientists as a sole method for identifying soil bacteria. We observed discrepancies with this method for identifying certain species of bacteria. Therefore, we used carbon substrate oxidation patterns (BIOLOG) and some simple physical and chemical tests to determine the extent of these discrepancies. Identification with FAME profiles gave false positives for Arthrobacter globiformis, Micrococcus kristinae, and M. luteus, and identification with BIOLOG patterns gave a false positive identification for A. globiformis. A visual check and Gram stain are recommended when FAME analysis identifies soil isolates as M. kristinae or M. luteus, and an additional spore formation test is recommended when FAME and BIOLOG analyses identify isolates as A. globiformis.
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    URL: http://dx.doi.org/10.1007/s003740000244
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    Production of root-derived material and associated microbial growth in soil at different nutrient levels (1987)
    Springer
    Biology and fertility of soils 5 (1987), S. 126-132 
    Details
    ISSN: 1432-0789
    Keywords: Residual soil 14C ; Microbial biomass ; Root-derived organic matter ; Fluorescent pseudomonads ; Rhizosphere ; Nutrient levels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Maize plants were grown for 42 days in a sandy soil at two different mineral nutrient levels, in an atmosphere containing 14CO2. The 14C and total carbon contents of shoots, roots, soil and soil microbial biomass were measured 28, 35 and 42 days after germination. Relative growth rates of shoots and roots decreased after 35 days at the lower nutrient level, but were relatively constant at the higher nutrient level. In the former treatment, 2% of the total 14C fixed was retained as a residue in soil at all harvests while at the higher nutrient level up to 4% was retained after 42 days. Incorporation of 14C into the soil microbial biomass was close to its maximum after 35 days at the lower nutrient level, but continued to increase at the higher level. Generally a good agreement existed between microbial biomass, 14C contents and numbers of fluorescent pseudomonads in the rhizosphere. Numbers of fluorescent pseudomonads in the rhizosphere were maximal after 35 days at the lower nutrient level and continued to increase at the higher nutrient level. The proportions of the residual 14C in soil, incorporated in the soil microbial biomass, were 28% to 41% at the lower nutrient level and 20%6 – 30% at the higher nutrient level. From the lower nutrient soil 18%6 – 52%6 of the residual soil 14C could be extracted with 0.5 N K2SO4, versus 14%6 – 16% from the higher nutrient soil. Microbial growth in the rhizosphere seemed directly affected by the depletion of mineral nutrients while plant growth and the related production of root-derived materials continued.
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    URL: http://dx.doi.org/10.1007/BF00257647
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    A sensitive method for measuring cyanide and cyanogenic glucosides in sand culture and soil (1987)
    Springer
    Biology and fertility of soils 5 (1987), S. 141-147 
    Details
    ISSN: 1432-0789
    Keywords: Cyanogenic glucosides ; Cyanide ; Root exudates ; Rhizosphere ; Linum usitatissimum ; Pteridium aquilinum ; Linamarase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Sensitive methods for measuring cyanide and cyanogenic glucosides in soil and sand culture have been developed. A microdiffusion technique is described which depends on the enzymic conversion of linamarin and lotaustralin to HCN, its release following acidification and incubation, and its detection in NaOH. Conditions for hydrolysis and HCN recovery have been optimised. The cyanide content of a silt loam soil (under non-cyanogenic wheat) was 5.47 nmol cyanide g−1 air-dried soil whilst that in an organic soil under the cyanogenic bracken, Pteridium aqgilinum, was 12.2 nmol g−1. Exudation of cyanogenic glucosides by linseed, Linum usitatissimum, was measured in plant growth tubes containing sand and a nutrient medium. Sterile plants exuded an average of 6.88 nmol glucosides plant−1 week−1 whilst, in contaminated tubes, the level fell to 4.72 nmol. Analysis of plant roots on each sampling occasion showed that 6.88 nmol was, on average, equivalent to 16.15% of the total root content of cyanogenic glucosides. There was a low but positive correlation between fresh weight of plant roots and the level of exuded glucosides. There was no evidence that plant roots produced free HCN.
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    Responses of nitrous oxide, dinitrogen and carbon dioxide production and oxygen consumption to temperature in forest and agricultural light-textured soils determined by model experiment (2000)
    Springer
    Biology and fertility of soils 32 (2000), S. 67-72 
    Details
    ISSN: 1432-0789
    Keywords: Key words Denitrification ; Nitrification ; Nitrous oxide ; Respiration ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The experiment, carried out on a forest and arable light-textured soil, was designed to study the temperature response of autotrophic and heterotrophic N2O production and investigate how the N2O flux relates to soil respiration and O2 consumption. Although N2O production seemed to be stimulated by a temperature increase in both soils, the relationship between production rate and temperature was different in the two soils. This seemed to depend on the different contribution of nitrification and denitrification to the overall N2O flux. In the forest soil, almost all N2O was derived from nitrification, and its production rate rose linearly from 2  °C to 40  °C. A stronger effect of temperature on N2O production was observed in the arable soil, apparently as a result of an incremental contribution of denitrification to the overall N2O flux with rising temperature. The soil respiration rate increased exponentially with temperature and was significantly correlated with N2O production. O2 consumption stimulated denitrification in both soils. In the arable soil, N2O and N2 production increased exponentially with decreasing O2 concentration, though N2O was the main gas produced at any temperature. In the forest soil, only the N2 flux was related exponentially to O2 consumption and it outweighed the rate of N2O production only at 〉34  °C. Thus, it appears that in the forest soil, where nitrification was the main source of N2O, temperature affected the N2O flux less dramatically than in the arable soil, where a temperature increase strongly stimulated N2O production by enhancing favourable conditions for denitrification.
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    URL: http://dx.doi.org/10.1007/s003740000218
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    The effect of fertilisation on soil nitrifier activity in experimental grassland plots (1988)
    Springer
    Biology and fertility of soils 5 (1988), S. 344-349 
    Details
    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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    Mechanistic model for nitrous oxide emission via nitrification and denitrification (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 231-238 
    Details
    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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    URL: http://dx.doi.org/10.1007/s003740050236
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    Seasonal, annual, and treatment-induced variation in available nitrogen pools and nitrogen-cycling processes in soils of two Douglas-fir stands (1988)
    Springer
    Biology and fertility of soils 6 (1988), S. 93-99 
    Details
    ISSN: 1432-0789
    Keywords: Ammonium ; Nitrate ; N-mineralization ; Nitrification ; Fertilization ; Irrigation ; Forest ecosystems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Forest-floor and 0–10 cm depth mineral soil horizons in two stands of Douglas fir were sampled for available NH4 +-N and NO3 −-N, N-mineralization potentials, and nitrification potentials for 2 years. The plots in each stand were sampled for 1 year, treated with either ammonium sulfate, carbohydrate (sawdust-sucrose), irrigation, carbohydrate plus irrigation, or no treatment (control), and then sampled for 1 year following treatment. In general, the direction of change following the treatments was the same for both the forest-floor and the mineral soils. Fertilization increased the NH4 +-N and NO3 −-N pools, nitrification potential, and N-mineralization potential, while treatment with carbohydrate decreased all of these characteristics. Irrigation generally increased NH4 +-N pools, nitrification potential, and N-mineralization potential, but decreased these characteristics in the soil at one site. Irrigation plus carbohydrate gave similar results to those of carbohydrate alone. Treatments altered pool sizes and/or potentials, but did not reduce within-year variance in any of these characteristics. Distinct seasonal patterns occurred in all measurements, suggesting that control of short-term variation in N-transformation processes is by factors which are dynamic in nature.
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    URL: http://dx.doi.org/10.1007/BF00257656
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  • 94
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    Relationships between soil moisture content and nitrous oxide production during nitrification and denitrification (1988)
    Springer
    Biology and fertility of soils 6 (1988), S. 106-111 
    Details
    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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    URL: http://dx.doi.org/10.1007/BF00257658
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  • 95
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    A method of selective inhibition to distinguish between nitrification and denitrification as sources of nitrous oxide in soil (1988)
    Springer
    Biology and fertility of soils 6 (1988), S. 112-119 
    Details
    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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    URL: http://dx.doi.org/10.1007/BF00257659
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  • 96
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    Root activity and carbon metabolism in soils (1988)
    Springer
    Biology and fertility of soils 7 (1988), S. 71-78 
    Details
    ISSN: 1432-0789
    Keywords: Root activity ; Rhizosphere ; C metabolism ; Microbial biomass ; Microbial activity ; Wheat ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Two different soils were amended with 14C-labelled plant material and incubated under controlled laboratory conditions for 2 years. Half the samples were cropped with wheat (Triticum aestivum) 10 times in succession. At flowering, the wheat was harvested and the old roots removed from the soil, so that the soil was continuously occupied by predominantly active root systems. The remaining samples were maintained without plants under the same conditions. During the initial stages of high microbial activity, due to decomposition of the labile compounds, the size of the total microbial biomass was comparable for both treatments, and the metabolic quotient (qCO2-C = mg CO2-C·mg−1 Biomass C·h−1) was increased by the plants. During the subsequent low-activity decomposition stages, after the labile compounds had been progressively mineralized, the biomass was multiplied by a factor of 2–4 in the presence of plants compared to the bare soils. Nevertheless, qCO2-C tended to reach similar low values with both treatments. The 14C-labelled biomass was reduced by the presence of roots and qCO2-14C was increased. The significance of these results obtained from a model experiment is discussed in terms of (1) the variation in the substrate originating from the roots and controlled by the plant physiology, (2) nutrient availability for plants and microorganisms, (3) soil biotic capacities and (4) increased microbial turnover rates induced by the roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00260736
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  • 97
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    Carbon and nitrogen accretion and dynamics in volcanic ash deposits from different subarctic habitats (1988)
    Springer
    Biology and fertility of soils 7 (1988), S. 79-87 
    Details
    ISSN: 1432-0789
    Keywords: Microbial biomass ; Mineralization ; Nitrification ; Subarctic ; Volcanic ash
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary C and N pool sizes and rates of mineralization were studied in volcanic-ash deposits found in different subarctic habitats in southwestern Alaska. Surface ash samples were taken from white-spruce, alder, and moist- and dry-tundra habitats and were analysed for total and microbial C and N. C and N dynamics were studied using a 28-day aerobic laboratory incubation, with weekly measurement of evolved CO2 and determination of inorganic-N pools initially and after 10 and 28 days. Total and microbial C and N and cumulative respired CO2 all followed a similar pattern among the different habitats, with the moist-tundra habitat having the highest values and the spruce site the lowest. The size of the microbial biomass C and N pool in the spruce habitat was among the lowest reported for any ecosystem. Little net N mineralization occurred in the spruce-forest and dry-tundra ash over 28 days. Ash from the moist-tundra habitat immobilized a significant amount of N during the first 10 days of incubation, yet showed a large net release of N after 28 days. In contrast, the ash from the alder site exhibited net mineralization after both periods, with N production after 28 days being about 3.5 times that after 10 days. In addition, the alder-habitat ash was the only soil that showed net nitrification. Rates of total C and N accretion in the tundra and alder habitats were rapid relative to rates found for primary successions. The results of this study show that habitat has a profound effect on C and N cycling in subarctic environments.
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    URL: http://dx.doi.org/10.1007/BF00260737
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  • 98
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    Long-term effects of different inorganic pollutants on nitrogen transformations in a sandy cambisol (1989)
    Springer
    Biology and fertility of soils 7 (1989), S. 254-258 
    Details
    ISSN: 1432-0789
    Keywords: N-mineralisation ; Nitrification ; Arginine ammonification ; Inorganic pollutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Long-term effects of 12 inorganic pollutants on N transformations were studied in a sandy cambisol. As, Be, Br, Cd, Cr, F, Pb, Hg, Se, Sn, and V were added to the soil as inorganic salts in 1975 and 1976. Soil samples were taken in 1984 to determine total N mineralisation and nitrification. All pollutants except Se and Sn inhibited N mineralisation. The most toxic elements under investigation were Be and Hg. Nitrification was reduced to a lower degree than total N mineralisation. As, Be, Cd, Cr, F, Pb, Se, and Sn failed to inhibit this process at all. It is assumed that nitrifying bacteria became adapted to these pollutants in the course of time. The arginine-ammonification method was less sensitive in detecting the effects of pollutants on N transformation than the N mineralisation test.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00709657
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  • 99
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    Electronic Resource
    Inoculation of rice with nitrogen-fixing bacteria —problems and perspectives (1987)
    Springer
    Biology and fertility of soils 4 (1987), S. 21-26 
    Details
    ISSN: 1432-0789
    Keywords: Bacterial inoculation ; Rice yield ; Associative nitrogen fixation ; Azotobacter spp. ; Azospirillum spp. ; Pseudomonas spp. ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The present status and merits of inoculating rice with N2-fixing bacteria are discussed in the light of recent advances. Bacterial inoculation improves plant growth and rice yield but not uniformly. The yield response to inoculation is more pronounced in the presence of moderate levels of fertilizer N. Evidence for the establishment and activity of the inoculated bacteria is limited, and the poor survival of the inoculum under field conditions further complicates the effects of inoculation. There is no clear evidence that improved growth and mineral content following inoculation are due to increased N2 fixation. Beneficial effects of the inoculum on rice, such as plant growth promotion, N2 fixation and antagonism effects against pathogens need to be further investigated under laboratory and field conditions. Improved management practices, such as organic amendments, suitable water and soil management, selection of efficient microbial strains, selection of effective breeding lines with high associative nitrogen fixation, and better management of agrochemicals are some of the measures suggested for deriving benefits from bacterial associations with rice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00280346
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  • 100
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    Organic and inorganic soil phosphates and acid phosphatase activity in the rhizosphere of 80-year-old Norway spruce [Picea abies (L.) Karst.] trees (1989)
    Springer
    Biology and fertility of soils 8 (1989), S. 128-133 
    Details
    ISSN: 1432-0789
    Keywords: Organic phosphates ; Rhizosphere ; Mycorrhizal roots ; Acid phosphatase ; Picea abies (L.) Karst. ; Norway spruce
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Inorganic and organic phosphates (P) were measured in bulk soil, rhizosphere soil and mycorrhizal rhizoplane soil of Norway spruce. Various methods of P extraction and estimation were compared. In addition, acid phosphatase activity and mycelial hyphae length were determined. In soil solutions from various locations, about 50% (range 35%–65%) of the total P was present as organic P. Compared to the bulk soil, the concentrations of readily hydrolysable organic P were lower in the rhizosphere soil and in the rhizoplane soil; this difference was particularly marked in the humus layer. In contrast, the concentrations of inorganic P either remained unaffected or increased. A 2- to 2.5-fold increase was found in the activity of acid phosphatase in the rhizoplane soil in comparison to the bulk soil. There was a positive correlation (r = 0.83***) between phosphatase activity and the length of mycelial hyphae. The results stress the role of organic P and of acid phosphatase in the rhizosphere in the P uptake by mycorrhizal roots of spruce trees grown on acid soils.
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    URL: http://dx.doi.org/10.1007/BF00257756
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