Reducing Nitrogen Emissions
Nitrogen fertiliser is a key nutrient that drives agricultural production. Ruminant livestock graze nitrogen-rich pasture or crops to produce meat or milk. However, some nitrogen is lost from the soil into the environment as a greenhouse gas called nitrous oxide (N₂O). N₂O can be released directly through the activity of micro-organisms in the soil called denitrifiers, or indirectly through nitrate (NO₃⁻) that leaches into water or ammonia (NH₃).
N₂O is a very strong greenhouse gas—about 265 times more powerful than carbon dioxide (CO₂)—and it can stay in the atmosphere for around 100 years. In Ireland in 2022, N2O accounted for 5 MTCO2e or 22.3% of agricultural GHG emissions (EPA, 2024).
Priority Research Questions
- Can precision N application, novel fertilisers and grazing management strategies reduce N₂O emissions and increase N use efficiency?
- What is the effect of soil type, land-use, management practice, sward type and weather on N₂O emissions?
- What is the interaction between soil nutrient status (i.e. soil index) and soil pH on N₂O emissions and N use efficiency?
- What is the impact of feeding diets with less crude protein in bovine and pig production systems on N use efficiency and N₂O emissions?
- What is the genetic variability in N use efficiency in grazing livestock and its impact on N₂O emissions?
Anticipated Research Outcomes
- Establishment of low nitrogen farming systems.
- Refinement of N₂O emission factors for fertiliser and a range of excreta across a range of soil types and land use/management systems.
- Refinement of NH3 emission factors for housing and manure storage and mitigation options to reduce emissions.
- Improved data collection relating to N fertiliser use, excretion, manure storage and land-spreading.
- Development of a Tier 3 model for quantification of N₂O emissions and nitrate leaching across a range of soil types, land-uses and management practices.
Dominika Krol
Nitrogen Pillar Lead
Research Snapshots
Clover
How Does It Work?
Clover fixes nitrogen from the atmosphere. Nitrogen fixation is the name of this process whereby white clover can fix N from the atmosphere and make it available for plant growth, thereby reducing the requirement for chemical Nitrogen.
Benefits of white clover
The benefits of white clover tend to occur from May onwards as sward white clover content increases. The main benefits of white clover inclusion in grass swards are:
- Increased herbage quality compared to grass-only swards in the summer months.
- Increased dry matter (DM) intake in summer and autumn.
- Higher milk production and live weight gain.
- Nitrogen fixation – white clover fixes nitrogen (N) from the atmosphere making it available for plant growth.
Cover Crops
Cover crops are species or mixtures of species grown over the autumn-winter period between two cash crops mainly for the purpose of generating some benefits for the cropping system rather that as cash crops themselves. Benefits of cover crops can include reduced nutrient loss, improvement of soil organic matter or carbon levels, reduced soil erosion, improved soil structural characteristics, improved biodiversity, reductions in pests and diseases of the following crops, increased nutrient supply to the following crop and yield benefits in the following cash crop.
Dr Richie Hackett presenting on Cover Crops on Irish Tillage Farms at the Signpost General Assembly in November 2024.
Read More
Current Projects on Reducing Nitrogen Emissions
Popular Publications from the Nitrogen Pillar
Signpost Webinar
The potential of plantain to reduce nitrate leaching in pasture systems - 4 April 2025