Despite the large quantity of research undertaken into the sustainability of food production and transportation systems, there is currently little consensus on the total contribution that greenhouse gas (GHG) emissions make to the overall GHG budget of food production systems. To date, most research has focused on the miles that food has travelled and the energy put into the production of pesticides and fertilisers associated with crop production. Understanding whether food imported from distant countries has a higher GHG footprint than locally produced food remains a very topical issue. Our fundamental lack of knowledge of this issue is limiting policy development in this area. Due to difficulties in field measurements mathematical models such as DNDC (DeNitrification DeComposititon) are being used to predict GHG emissions from different ecosystems. In this thesis, a combination of field measurements and model simulations were used to evaluate GHG emissions from different agricultural production systems undertaken in different countries (UK, Spain and Kenya). This thesis also considered the accuracy of the model by undertaking a sensitivity analysis and evaluating the outputs from different model versions. In addition, the accuracy of using a QIO value approach to predict organic matter degradation was also evaluated. Overall, the results suggested that different model versions gave varying outputs, suggesting that predictions of GHG emissions obtained with models such as DNDC should be treated with caution. However, the model did predict similar results to those obtained in the field, although the model outputs tended to be higher. For comparison of GHG emissions from vegetable types grown in different geographical regions, no specific region produced lower GHG results when averaged across all crops. However, when individual crops were considered, Spain had the highest GHG emissions. The models showed different degrees of sensitivity to different inputs, with some not showing any variation at all. In the Q10 evaluation experiments the Q10 values varied greatly, though all gave results above the standard Q10 of 2. Further research is needed into the accuracy of climate and farm management models, and whether or not it is necessary to compare large data sets when considering different vegetable types and areas.
|Source Sets||Ethos UK|
|Type||Electronic Thesis or Dissertation|
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