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  • 1
    Electronic Resource
    Electronic Resource
    Microbial population dynamics related to temporal variations in nitrification in three arable fields (2003)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 54 (2003), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: It seems possible that soil potential nitrification rates (PNRs) are determined by the size and structure of both the eubacterial and nitrifier populations. We have examined this possibility by comparing the structure of the eubacterial community with the subcomponents and dynamics of the ammonium-oxidizer population, within and between three arable fields. PNRs were significantly different between the three fields and also showed significantly different temporal patterns within each field. The use of eubacterial primers in polymerase chain reaction–denaturing gel gradient electrophoresis (PCR–DGGE) analyses indicated that the bacterial community structure in each field was significantly different from that in the others, and that the bacterial components of these communities changed with time through the season. In contrast, PCR–DGGE analyses specific to ammonium oxidizers suggested that the populations in all three fields were similar in types and did not vary with time. Competitive PCR suggested that there were large and biologically significant differences in the size of the nitrifier population between the three fields, but that within each individual field populations did not change over time. Sequencing identified the ammonium oxidizers in the Nitrosospira spp. cluster. There was also no relation between the size of the nitrifier populations and PNR. Functional expression, as PNR, apparently responded to changes in eubacterial community structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1351-0754.2003.0558.x
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  • 2
    Electronic Resource
    Electronic Resource
    Why plants bother: root proliferation results in increased nitrogen capture from an organic patch when two grasses compete (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 22 (1999), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We investigated whether the capacities of Lolium perenne L. and Poa pratensis L. roots to proliferate locally and to alter local nitrogen (N) inflows in a decomposing organic matter patch were important in their capture of N when grown together. In the presence of a patch, plants of both species were significantly heavier and contained more N. Root length and weight densities increased in the patch, but specific root length was unaltered. Although both species proliferated roots in the patch, L. perenne produced greater root length densities than P. pratensis, and also captured more N from the patch. Indeed, total N uptake from the patch was related to root length density within the patch. N inflows (rate of N uptake per unit root length) in the patch were no faster than in the whole root system for both species. Under the conditions of this study, root proliferation in an organic patch was more important for N capture from the patch than alterations in N inflows. Local proliferation of roots may be a key factor in interspecific competition for non-uniformly distributed supplies of N in natural habitats, so resolving the previous uncertainty as to the ‘adaptive’ nature of root proliferation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1999.00454.x
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  • 3
    Electronic Resource
    Electronic Resource
    Biological and physical resilience of soil amended with heavy metal-contaminated sewage sludge (2005)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    European journal of soil science 56 (2005), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Stability and resilience of a variety of soil properties and processes are emerging as key components of soil quality. We applied recently developed measures of biological and physical resilience to soils from an experimental site treated with metal-contaminated sewage sludge. Soils treated with cadmium-, copper- or zinc-contaminated, digested or undigested sewage sludge were studied. Biological stability and resilience indices were: (i) the time-dependent effects of either a transient stress (heating to 40°C for 18 hours) or a persistent stress (amendment with CuSO4) on decomposition, and (ii) the mineralization of dissolved organic carbon (DOC) released by drying–rewetting cycles. Physical stability and resilience measures were: (i) compression and expansion indices of the soils, and (ii) resistance to prolonged wetting and structural regeneration through drying–rewetting cycles. Soil total carbon and DOC levels were greater in the sludge-amended soils, but there were no differential effects due to metal contamination of the sewage sludge. Effects of metals on physical resilience were greater than effects on soil C, there being marked reductions in the expansion indices with Cd- and Cu-contaminated sludge, and pointed to changes in soil aggregation. The rate of mineralization of DOC released by drying and wetting was reduced by Zn contamination, while biological resilience was increased in the Zn-contaminated soil and reduced by Cd contamination. We argue that physical and biological resilience are potentially coupled through the microbial community. This needs to be tested in a wider range of soils, but demonstrates the benefits from a combined approach to the biological and physical resilience of soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2389.2004.00667.x
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  • 4
    Electronic Resource
    Electronic Resource
    Huge increase in bacterivores on freshly killed barley roots (1992)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 9 (1992), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1992.tb01765.x
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  • 5
    Electronic Resource
    Electronic Resource
    Application of an augmented nitrification assay to elucidate the effects of a spring barley crop and manures on temporal variations in rates (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 378-383 
    Details
    ISSN: 1432-0789
    Keywords: Key words Nitrification ; Manures ; Organic farming ; Controlling factors ; Augmented nitrification assay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of crop plants and farmyard or poultry manure applications on temporal variations in nitrification rates were measured in a field experiment. In order to elucidate factors which may have been governing such rates, an augmented nitrification assay was applied. The basis of the assay was to measure nitrification rates under circumstances where substrate, i.e. ammonium-ion, and water and spatial constraints had been removed. Nitrification rates showed marked temporal variation, of over one order of magnitude, throughout the growing season. Nitrification rates were also similarly increased when substrate and spatial constraints were removed, but distinct temporal variations still persisted. The pattern of such variations varied according to assay conditions in the augmented nitrification assay. Barley plants had a statistically significant effect on nitrification rates, positive early in the growing season and negative at the end. Manures stimulated nitrification, with poultry manure having a greater effect than farmyard manure, and there was evidence for a relationship between heterotrophic and autotrophic activity. Factors other than ammonium-ion concentration and water or spatial restrictions must also regulate nitrification rates in mineral soils; these could include population size or interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050261
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of animal manure application and crop plants upon size and activity of soil microbial biomass under organically grown spring barley (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 372-377 
    Details
    ISSN: 1432-0789
    Keywords: Key words Microbial biomass ; Organic farming ; Soil respiration ; Farmyard manure ; Poultry manure ; Hordeum vulgare ; Barley ; Fumigation extraction ; technique ; Fumigation incubation technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Temporal behaviour of microbial biomass C, N and respiration was measured under barley crops in two experiments on successive years in a recently converted organic production system in Scotland. Soils were fertilised with farmyard manure or poultry manure. Control soils received no manure at the start of the growing season. The effects of plants was also investigated by maintaining fallow subplots. C-flush values approximately doubled over the growing season in both years of the trial, showing a decline to pre-sowing values between the two seasons. This occurred in all soils, whether manured or not, or planted or fallow. Manure tended to increase the C-flush in the 2nd year only. N-flush in the 2nd year showed no increase in planted control plots but did increase in fallow soils. Manures significantly increased the N-flush. Respiration rates were stimulated by the presence of plants. Respiration rates were measured from soils taken from the field at post-sowing, mid-season and post-harvest occasions and incubated under constant conditions for up to 1 year. Here there was evidence that the effects of sampling and adjusting the moisture status could be as great upon microbial activity as the addition of the manures. C-flush also showed a consistent and persistent increase in these incubated soils. This suggests that the fundamental C-supplying characteristics of these soils was such that the biomass was moving towards a new equilibrium value fuelled by the relatively recent introduction of the organic farming regime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050260
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  • 7
    Electronic Resource
    Electronic Resource
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335867
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  • 8
    Electronic Resource
    Electronic Resource
    The effect of nitrate-nitrogen supply on bacteria and bacterial-feeding fauna in the rhizosphere of different grass species (1992)
    Springer
    Oecologia 91 (1992), S. 253-259 
    Details
    ISSN: 1432-1939
    Keywords: Bacteria ; Enchytraidae ; Nematoda ; Nitrogen ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Microbial growth in the rhizosphere is affected by the release of organic material from roots, so differences in carbon budgets between plants may affect their rhizosphere biology. This was tested by sampling populations of bacteria and bacteriophagous fauna from the rhizosphere of Lolium perenne, Festuca arundinacea, Poa annua, and Poa pratensis, under conditions of high and low nitrate availability. Concentrations of soluble phenolics and lignin varied considerably between the species but were not related to differences in rhizosphere biology. L. perenne and F. arundinacea supported fewer bacteria than the Poa species. There was no significant rhizosphere effect on the groups of protozoa. The major indicators of rhizosphere productivity were the bacterial-feeding nematodes (mainly Acrobeloides spp.), and there was a large positive effect of added nitrate. Nematode biomass was significantly lower in the rhizosphere of the slow-growing P. pratensis compared with the fast-growing P. annua, indicating that the differential allocation of carbon has affects on rhizosphere biology. A large rhizosphere effect on enchytraeid worms was also observed, and their potential importance in the rhizosphere is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317793
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  • 9
    Electronic Resource
    Electronic Resource
    Variations in the rates of nitrification and denitrification during the growth of potatoes (Solanum tuberosum L.) in soil with different carbon inputs and the effect of these inputs on soil nitrogen and plant yield (1991)
    Springer
    Biology and fertility of soils 11 (1991), S. 157-162 
    Details
    ISSN: 1432-0789
    Keywords: Carbon ; Denitrification ; Immobilisation ; Mineralisation ; Nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A potato crop (Solanum tuberosum L. cv. Maris piper) was grown in a soil to which N was added, as NH4NO3, with or without added C, as sucrose or straw. Shortly after amendment the soil, in all treatments, contained only relatively low levels of mineral N. However, these levels increased later. The increase, which was greatest in the absence of added C and least with added sucrose, occurred before the emergence of the plant canopy. The addition of C to the soil had no effect on plant yield, measured either as dry matter or total N content. The potential nitrification rate was high early in the season, and decreased significantly as the plants developed. The potential denitrification rate showed two significant peaks in activity, possibly related to plant development, the first to the development of new roots and the second to root senescence. It seems probable that the amount of C released by the potato plants was only about one-quarter of that required for the maximum microbial activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336382
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  • 10
    Electronic Resource
    Electronic Resource
    Soil microbial biomass and activity under a potato crop fertilised with N with and without C (1992)
    Springer
    Biology and fertility of soils 12 (1992), S. 265-271 
    Details
    ISSN: 1432-0789
    Keywords: Dehydrogenase activity ; Microbial biomass C ; Microbial biomass N ; N fertisisation ; C additions ; Soil respiration ; Solanum tuberosum L. ; Substrate-induced respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A range of soil microbiological parameters were measured at intervals throughout the growing season of a potato crop. Treatments applied to the soil at sowing were zero N fertilisation of N fertilisation at 120 kg N ha−1, either alone or supplemented with straw or sucrose at 1200 kg C ha−1. C and N flushes determined by fumigation-incubation and fumigation-extraction, and substrate-induced respiration, were measured as indicators of microbial biomass. Microbial activity was measured as respiration (CO2 production) and dehydrogenase activity (formazan production). The greatest effects were obtained from the addition of N plus sucrose. Both biomass size and activity were significantly stimulated for up to 25 days after incorporation, with the magnitude of the effects consistently diminishing over time. By 125 days after planting, there was no detectable legacy from any of the treatmentson any of the biomass parameters that were measured, and all values had reverted to those prevalent at planting. There was no consistent effect from adding N, either alone or supplemented with straw, on any of the biomass parameters. There was no evidence for crop-induced stimulation of the biomass. The experiment demonstrates that biomass is only influenced where the quantity, quality, and rate of incorporation of C into the soil is appropriate, in this case, only by adding C as a pulse of sucrose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336042
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