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Title: Evaluation of fertiliser formulations on grassland N use efficiency and nitrous oxide emissions
Author: Harty, Mary
ISNI:       0000 0004 6058 3682
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2016
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Obligations to reduce greenhouse gas emissions (GHG) in agriculture (30% below 1990 levels by 2030) have seen renewed interest in switching from ammonium nitrate (AN) based to urea based fertilisers as a mitigation strategy for GHG emissions. The performance of a comprehensive range of urea based formulations was compared to Calcium AN in a two-year study over three sites across the island of Ireland. The performance criteria were nitrous oxide (N2O) emissions, ammonia (NH3) emissions, grassland yield and N uptake encompassing a range of soils and climatic conditions. The results of the main field experiments showed that all urea formulations reduced N2O emissions relative to CAN in all site-years with larger reductions under the heavier and wetter soil conditions. The inclusion of the urease inhibitor NBPT also reduced NH3 emissions relative to urea and maintained yield and N uptake relative to CAN in all six site-years. In contrast, the nitrification inhibitor dicyandiamide (DCD) showed inconsistent effects on NH3 emissions compared to urea and reduced yield and N uptake relative to CAN in three and four of six site-years respectively. The most climate favourable option was urea incorporating NBPT, however as it is more expensive than urea, a tax on urea or financial incentive to use NBPT will be required to ensure farmers select the stabilised urea incorporating NBPT over urea. In addition, the assessment of N2O emissions from the same fertilisers also contributes to a more detailed accurate national inventory of mineral fertiliser N2O emissions. The tier 1 reporting of emission factors (EF) under the Intergovernmental Panel on Climate Change (IPCC) requirements uses a default EF for N2O from soils of 1% of the N applied, irrespective of its form even though N2O emissions tend to be higher from nitrate-containing fertilisers compared to urea. This research generated tier 2 emission factors for mineral N fertiliser by formulation and soil type.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available