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Title: Microbial processes contributing to N₂O production in two sandy Scottish soils
Author: Castaldi, Simona
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1998
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The objective of the present work was to investigate the potential contribution of different microbial processes to N2O fluxes and the influence of the main environmental factors on these processes in two light textured Scottish soils. Two imperfectly drained brown forest soils of the Peffer Series, derived from fine beach sand, were studied. One was a sandy loam, sampled from a deciduous woodland and the other was a loamy sand, sampled from a nearby winter wheat field, at Gullane, East Lothian, Scotland. Both soils had slightly alkaline pHs. Field and laboratory studies showed that more than one process was responsible for N2O emissions. One source was yielding quite low fluxes (1.4 - 1.5 g N2O-N ha-1 yr-1) throughout the year and had a certain seasonality. A second source involved different processes which were yielding higher N2O fluxes and were favoured by the presence of high concentrations of mineral N and fresh organic matter. The arable soil showed a very low potential for N2O production from nitrifiable N2 by comparison with the N2O which was produced when the soil was provided with oxidized N (NO2- and NO3-) and a carbon source. A very active population of denitrifiers, probably adapted to predominantly aerobic conditions, seemed responsible for the fast rate of nitrate consumption and N2O production in the laboratory. It appears, therefore, that light soils could contribute significant N2O fluxes from denitrification, if fertilized with nitrate in the presence of readily decomposable organic matter. These conditions, however, were rare in the arable soil, which showed extremely low fluxes during the whole year. These fluxes were probably due to bacterial oxidation of the small quantity of NH4+ released by mineralization. The woodland soil had a very low rate of denitrification activity but a much higher N2O production via HN4+ oxidation and reduction of NO2- by some process mediated by autotrophic or heterotrophic nitrifiers, of which fungi could be an important component. Though results seemed to support this latter hypothesis, more evidence is needed on this aspect.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available