Tillage Farmers in a unique position
Michael Hennessy, Head of Teagasc Crops Knowledge Transfer Department, tells us how tillage farmers are in a unique position with the lowest greenhouse gas output per hectare.
The tillage farmers of Ireland are in a unique position compared to other enterprises. The sector has the lowest greenhouse gas output per hectare compared to cattle rearing, which is four times higher, and the dairy sector which is eight times higher. The sectors emissions are small but there are emissions nonetheless and we should be trying all methods possible to reduce these even further. Nitrogen is the largest contributor to these emissions, accounting for roughly 80% of the emissions. Reductions can be achieved by increasing nitrogen use efficiency by reducing the total applied, replacing chemical N with organic N or changing to a legume crop ( beans/peas) to eliminate the need for nitrogen altogether.
James Doran, Teagasc Advisor caught with Michael Hennessy, Head of Crops KT, Teagasc at #Ploughing2022 to discuss cover crops and soils. Generally tillage soils can have somewhere between 2% and 5% of carbon in the soils. The earlier you sow cover crops, the more nitrogen they are going to capture between one spring barley and the next spring barley. The earlier you sow them in the more you're going to get out of them.
Long term grass ley generally have high soil organic carbon content and can have limited potential to increase these levels further. As many of soils may have reached an equilibrium of organic matter over time therefore applying organic manures, such as farm yard manures or slurries may not result in capturing the embedded organic carbon into the soil.
Soils which have been in tillage for some time (10+ years) tend to have lower soil carbon or soil organic carbon. The process of cultivation will “burned off” soil carbon and the more intensive the cultivation the greater the loss. However on the other side of the coin this creates an opportunity as tillage soils readily accept organic matter and can build soil carbon levels over time.
There are a number of ways which organic carbon can be added to the soil which include; returning straw residues, growing cover crops and applying organic manures. The additional benefits of increasing organic carbon in the soil are many including a healthier and more resilient soil to stresses like drought, water logging, compaction, etc. Build up of soil carbon is not easy and takes time. Any increases are slow, with little progress over a period of 2-3 years, and it can be as long as 10-15 years before significant increases can be observed.