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  • Key words Nitrous oxide  (3)
  • Brassica  (2)
  • Springer  (5)
  • Blackwell Publishing Ltd
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  • Springer  (5)
  • Blackwell Publishing Ltd
  • 1
    ISSN: 1432-0789
    Keywords: Key words Nitrous oxide ; Clover ; Herb ley ; Soil pH ; Allium cepa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  N2O emissions were measured from three contrasting onion (Allium cepa L.) production systems over an 8.5-month period. One system was established on soil where a clover sward had 3 months earlier been ploughed in (ploughed clover site). This production system followed conventional production management practices. The other two systems were established on soil where a mixed herb ley had 3 months earlier been either ploughed or rotovated. These last two production systems followed the guidelines of the International Federation of Organic Agriculture Movements (IFOAM). Cumulative N2O emissions were significantly greater from the ploughed clover site compared to the ploughed ley site (3.8 and 1.6 kg N2O-N ha–1, respectively), while cumulative N2O emissions from the ploughed ley and rotovated ley sites were not significantly different from each other. Emissions from all sites were dominated by episodes of high N2O flux activity following seedbed preparation and drilling, when soil water suction (SWS) was shown to be the rate-controlling variable. The decline in the N2O fluxes after these peak emissions followed clear exponential relationships of the form F=Ae– kt (r≥0.91), where F is the daily flux and A is the y-intercept. First-order decay constants (k) during these periods of declining N2O fluxes (corresponding to half-lives of 2.6–3.0 days) were not significantly different in magnitude from the first-order rate constants that characterised the increasing SWS. Gross differences in cumulative emissions between the clover and ley sites were attributed to the influence of differing soil pHs at the two sites on the N2O:(N2O+N2) ratio in the denitrification products. It also appeared that fertiliser applications to the clover site had both direct and indirect effects on N2O emissions by: (1) enhancing N2O emissions via potential nitrification, (2) increasing the NO3 – supply for enhanced N2O emissions via denitrification, and (3) influencing the N2O:(N2O+N2) ratio by lowering soil pH and increasing NO3 – concentrations. Onion crop yields were greater at the clover site, mainly due to the higher density of planting made possible under a conventional production philosophy. Expressing the yield on the basis of net N2O emissions, 23 t onions kg–1 N2O-N was obtained from the ploughed clover, which was double that obtained for the two systems based on the ley site. However, when the N2O emissions from the cultivation of the soils prior to the sowing of the onions was included, all three systems produced a similar yield per kilogram of N2O-N emitted, averaging 10 t kg–1.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 28 (1998), S. 51-55 
    ISSN: 1432-0789
    Keywords: Key words Nitrous oxide ; Nitrification ; Denitrification ; Soil cores ; Acetylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Nitrous oxide (N2O) emissions via the nitrification (I nit) and denitrification (I den) pathways were successfully measured with in-field incubation of soil cores in preserving jars at 0 Pa and 5–10 Pa acetylene. From the incubations, fractions of nitrification – N2O over total N2O (I nit / I tot) – and denitrification – N2O over total N2O (I den / I tot) – were obtained. Actual field emissions of N2O via nitrification (F nit) and denitrification (F den) were calculated by multiplying the fractions from the incubation technique with the daily N2O emission (F day) determined with a direct soil cover method. The approach presented here was successful for a whole range of soil moisture conditions in intensive grassland. F nit and F den followed the trends of soil ammonium and soil nitrate.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0789
    Keywords: Key words Nitrous oxide ; Methane ; Clover ; Herb ley ; Cultivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Nitrous oxide (N2O) emissions and methane (CH4) consumption were quantified following cultivation of two contrasting 4-year-old pastures. A clover sward was ploughed (to 150–200 mm depth) while a mixed herb ley sward was either ploughed (to 150–200 mm depth) or rotovated (to 50 mm depth). Cumulative N2O emissions were significantly greater following ploughing of the clover sward, with 4.01 kg N2O-N ha–1 being emitted in a 48-day period. Emissions following ploughing and rotovating of the ley sward were much less and were not statistically different from each other, with 0.26 and 0.17 kg N2O-N ha–1 being measured, respectively, over a 55-day period. The large difference in cumulative N2O between the clover and ley sites is presumably due to the initially higher soil NO3 – content, greater water filled pore space and lower soil pH at the clover site. Results from a denitrification enzyme assay conducted on soils from both sites showed a strong negative relationship (r=–0.82) between soil pH and the N2O:(N2O+N2) ratio. It is suggested that further research is required to determine if control of soil pH may provide a relatively cheap mitigation option for N2O emissions from these soils. There were no significant differences in CH4 oxidation rates due to sward type or form of cultivation.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 75 (1988), S. 784-794 
    ISSN: 1432-2242
    Keywords: Brassica ; Genome evolution ; Phylogenetic tree ; Molecular taxonomy ; Restriction fragment length polymorphisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Restriction fragment length polymorphisms (RFLPs) of nuclear DNAs have been used to explore the origin and evolution of the six cultivated Brassica species. Extensive RFLP variation was found at the species, subspecies and variety levels. Based on RFLP data from Brassica and related genera, a detailed phylogenetic tree was generated using the PAUP microcomputer program, which permits a quantitative analysis of the interrelationships among Brassica species. The results suggested that 1) B. nigra originated from one evolutionary pathway with Sinapis arvensis or a close relative as the likely progenitor, whereas B. campestris and B. oleracea came from another pathway with a possible common ancestor in wild B. oleracea or a closely related nine chromosome species; 2) the amphidiploid species B. napus and B. juncea have evolved through different combinations of the diploid morphotypes and thus polyphyletic origins may be a common mechanism for the natural occurrence of amphidiploids in Brassica; 3) the cytoplasm has played an important role in the nuclear genome evolution of amphidiploid species when the parental diploid species contain highly differentiated cytoplasms. A scheme for the origins of diploid and amphidiploid species is depicted based on evidence gathered from nuclear RFLP analysis, cpDNA RFLP analysis, cytogenetic studies and classical taxonomy.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 79 (1990), S. 497-506 
    ISSN: 1432-2242
    Keywords: Brassica ; Molecular taxonomy ; Genome evolution ; Phylogenetic analysis ; Restriction fragment length polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary RFLPs were used to study genome evolution and phylogeny in Brassica and related genera. Thirtyeight accessions, including 10 accessions of B. rapa (syn. campestris), 9 cultivated types of B. oleracea, 13 nine-chromosome wild brassicas related to B. oleracea, and 6 other species in Brassica and allied genera, were examined with more then 30 random genomic DNA probes, which identified RFLPs mapping to nine different linkage groups of the B. rapa genome. Based on the RFLP data, phylogenetic trees were constructed using the PAUP microcomputer program. Within B. rapa, accessions of pak choi, narinosa, and Chinese cabbage from East Asia constituted a group distinct from turnip and wild European populations, consistent with the hypothesis that B. rapa had two centers of domestication. A wild B. rapa accession from India was positioned in the tree between European types and East Asian types, suggesting an evolutionary pathway from Europe to India, then to South China. Cultivated B. oleracea morphotypes showed monophyletic origin with wild B. oleracea or B. alboglabra as possible ancestors. Various kales constitute a highly diverse group, and represent the primitive morphotypes of cultivated B. oleracea from which cabbage, broccoli, cauliflower, etc. probably have evolved. Cauliflower was found to be closely related to broccoli, whereas cabbage was closely related to leafy kales. A great diversity existed among the 13 collections of nine-chromosome wild brassicas related to B. oleracea, representing various taxonomic states from subspecies to species. Results from these studies suggested that two basic evolutionary pathways exist for the diploid species examined. One pathway gave rise to B. fruticulosa, B. nigra, and Sinapis arvensis, with B. adpressa or a close relative as the initial ancestor. Another pathway gave rise to B. oleracea and B. rapa, with Diplotaxis erucoides or a close relative as the initial ancestor. Raphanus sativus and Eruca sativus represented intermediate types between the two lineages, and might have been derived from introgression or hybridization between species belonging to different lineages. Molecular evidence for an ascending order of chromosome numbers in the evolution of Brassica and allied genera was obtained on the basis of RFLP data and phylogenetic analysis.
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