Recent research update from Teagasc on climate is released

Measuring soil carbon stocks on farms

During the deep soil-sampling campaign in 2023-2024, over 1,000 samples were taken from 268 soil profiles on 67 Signpost farms for carbon analysis.

On each farm, the main soil types were identified and used to mark sampling locations to capture the combinations, agricultural systems and land management practices and soils. Samples were taken at four soil depths (0-15, 15-30, 30-45 and 45-60cm).

Early results show that soil organic carbon (SOC) stock values for our farms ranged from 48-199t C/ha, down to 60cm.

Tillage farms overall exhibited the lowest SOC stocks, with an average of 90t C/ha stock down to 60cm in the profile.

In contrast, SOC stocks in permanent grasslands were higher, with an average of 97t C/ha recorded within the full soil profile, with most of this (46t C/ha) concentrated in the first 15cm, which is 32% higher than values in croplands.

Carbon stocks in Irish soils are higher compared to Mediterranean soils. These results represent the stock of carbon stored and not the amount or rates sequestered.

Cutting emissions from slurry management on farms

Managing manure effectively is crucial for reducing agricultural emissions, as manure storage and animal housing are responsible for over 12% of greenhouse gas emissions, and nearly half of ammonia emissions.

These gases, including methane and nitrous oxide, are released during manure storage and application.

One way to reduce these emissions is through the use of slurry additives like acids, which can help cut down on ammonia and methane during storage.

However, slurry applied to soil can release nitrous oxide, and some slurry amendments may increase emissions when the manure is spread on land, due to higher nitrogen content.

Teagasc and AFBI research is examining the impact of low-emission slurry-spreading methods and slurry acidification on soil emissions.

Early results show that nitrous oxide emissions from soil are lower than expected, with no difference between spreading methods, or between acidified and un-acidified slurry.

These results are important, as they show that while reducing ammonia and methane emissions during manure storage is beneficial, it does not appear to cause higher emissions when the slurry is applied to fields.

Balancing the benefits and emissions: the role of lime in sustainable Irish farming

Lime has traditionally been used to neutralise soil acidity, improve nutrient availability, and improve grass and crop growth.

Liming of soil also releases nitrogen from the soil organic matter pool, reducing nitrogen fertiliser requirements.

In addition to the agronomic benefits of lime, Teagasc research has also found that increasing soil pH to between 6.5 and 7 can reduce the loss of the potent greenhouse gas nitrous oxide by 40%.

Liming is an important measure to reduce agricultural emissions and the target is to increase lime use to 2.5m tonnes by 2030.

However, it’s important to note that lime itself contributes to greenhouse gas emissions.

When lime is applied to soil, carbon dioxide is released back into the atmosphere. In 2022, lime accounted for 0.626 MtCO2e or 3% of agricultural emissions, with this figure expected to rise by 30% by 2030.

Emissions from lime are relatively small and the benefits of liming outweigh them. Ongoing research by Teagasc and AFBI under the LABMACC project aims to develop country-specific emission factors for lime.

This research is expected to lead to a reduction in lime’s emission factor, ultimately helping to lower agricultural emissions in Ireland.