Experiments were conducted at the University of Aberdeen under controlled laboratory conditions to examine the interactive effect of combining crop residues barley (<i>Hordeum vulgare</i>), clover <i>(Trifolium pretense)</i>, cowpea (<i>Vigna unguiculata</i>), <i>Leucaena (Leucena leucocephala</i>) and <i>Mucuna (Mucuna pruriens)</i> and inorganic N fertiliser on N<sub>2</sub>O emission and mineral N dynamics. Emissions of N<sub>2</sub>O increased following sole application of the residues dependent on their utility or chemical composition. In general emissions were significantly higher from soils amended with low C:N ratio clover, cowpea, <i>Leucena </i>and <i>Mucuna </i>residues compared to the high C:N ratio barley species. N<sub>2</sub>O emission was further increased following combined application of crop residues and inorganic N fertiliser but the magnitude of emission was influenced by the proportional ratios at which the residue-N and the fertiliser-N were combined, and the C:N ratio, lignin and polyphenols contents of the residues, with the low lignin and low polyphenols cowpea treatment emitting higher N<sub>2</sub>O over 30 days compared to the high lignin <i>Mucuna </i>and the high polyphenols <i>Leucena </i>treatments. Results from experiments demonstrated that whilst there is the potential for N<sub>2</sub>O emission to be controlled through varying ratios of residue:fertiliser input, the magnitude and direction of interactions between these N sources varies between different species as a result of their differing qualities. Based on our applications of <i>Leucaena, Mucuna </i>and cowpea residues, the 75:25 residue: fertiliser ratio at 100 mg N kg<sup>-1</sup> soil is recommended from this study as offering the best compromise between release of N for crop uptake and management of N<sub>2</sub>O emission, but this requires further investigation at field scale.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:540326 |
| Date | January 2010 |
| Creators | Frimpong, Kwame Agyei |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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