At the recent Tullamore Farm Open Day, there was huge interest in the farm’s soil carbon results and soil carbon in general.
Soils on the farm were sampled to a depth of 30cm last May and tested for soil carbon in the lab. The results are shown in the map above right.
The lowest level of soil carbon per hectare was 21.9t/ha and the highest was 98.8t/ha. The average soil carbon level on the farm was 61.1t/ha.
In total, there are 4,930.7t of carbon currently stored in the top 30cm of the soil on Tullamore Farm.
We will test all these areas again in about three years’ time and if the total amount of carbon stored in the soils on the farm increases during this period, this will have helped to offset emissions created on the farm. However, farmers are not rewarded for this sequestration at present. It is accounted for in the country’s national inventory.
Why did results differ?
It was clear from the soil carbon results that soil type and management had an impact on soil carbon levels.
The land on the outfarm in Cloona had the lowest soil carbon levels, as it had been in long-term tillage. The land around the farmyard was generally higher in carbon than the rest of the farm.
For example, the field next to the farmyard had 88.4t/ha of carbon in the top 30cm of the soil. This may have had animals grazing more regularly and may have gotten more slurry or farmyard manure than the rest of the farm due to its proximity to the yard.
The land across the road from the farmyard is wetter and more peaty, compared to the sandy land around the yard itself. Soil carbon levels are generally higher on this land.
There is a lot of room to increase soil carbon levels on Tullamore Farm, as the carbon content in general is fairly low. Also, there is potential to increase some fields quicker than others.
The continuous tillage land in Cloona could increase significantly with the addition of grazing animals and organic manures. However, carbon can also be released during reseeding for example.