Based on the data from the Teagasc National Farm Survey sustainability reports over the past few years, tillage farmers emitted the equivalent of just over 2.3t CO2-e/ha.

However, when the livestock proportion is stripped out of these farms, the tillage proportion is just over 1.2t CO2e/ha.

When we compare this to other systems, cattle farms emit close to 4.5t CO2-e/ha and dairy farms close to 9.2t CO2-e/ha.

So, the starting point is that tillage farms are low emitters of CO2 equivalents per hectare.

How can this be improved?

The biggest contributor to greenhouse gas (GHG) emissions on tillage farms is nitrogen use. This input alone can account for 80% to 85% of all emissions per year.

These emissions come in two forms:

  • From the manufacture of NPK.
  • From the release of nitrogen in the form of N2O (nitrous oxide) and indirect emissions from leached nitrate.
  • The losses are associated with nitrous oxide lost to the air and nitrate leaching to groundwater.

    The N2O lost in a tillage systems is relatively low even when using CAN and a little lower if using urea, but it’s still relatively small.

    However, the losses of nitrate through the late summer and autumn can be significant in free-draining soils, which are mainly tillage soils.

    We also know from reports published by the Environmental Protection Agency that rivers in the main tillage catchments, particularly in the southeast, have high nitrate values and a proportion of this nitrate comes from tillage soils.

    So, with all that said, targeting nitrogen use on tillage farms is a sensible place to start to reduce GHG emissions, although the overall reductions will be small.

    Considering the cost of nitrogen in 2022, it’s a good year for farmers to look at ways to reduce nitrogen use on farm.

    There are a number of ways to reduce nitrogen use, including growing your own nitrogen by using leguminous crops, reducing nitrogen inputs by using less and increasing the precision of application.

    Use an alternative source of nitrogen by using organic manures and change the source of your nitrogen. We will look at these one by one.

    Grow your own nitrogen from leguminous crops

    Beans are a crop many people may have tried over the past 10 years. The crop can suffer from yield inconsistency and when the crop is poor, it can be very poor, like in 2018.

    However, growers who plant the crop on time, on the correct land and manage it carefully are achieving quite consistent yields year-on-year.

    Increasing the area of beans can significantly reduce fertiliser requirements. Take an example of an 80ha farm, growing winter barley (20ha), spring barley (56ha) and a small amount of beans (4ha).

    If the cropping is adjusted, where winter barley would stay the same (as it is already planted) and the farm maximises the area of beans (eg beans one in every five years) and reduce the amount of spring barley sown.

    This reduces the farm’s nitrogen requirement by 14% or close to 7t of CAN (or €4,340 at €620/t for CAN).

    These are significant savings and the overall profitability of the farm will not be compromised.

    Reducing nitrogen below the optimum rate for yield is tricky

    Nitrogen recommendations for crops are based on the economic optimum. This rate generally builds in a little extra nitrogen to ensure high yield, but not necessarily the highest yield.

    Increasing nitrogen above this level (eg 210 kg N/ha for winter wheat or 135kg N/ha for spring barley) does not guarantee a higher yield; rather, it is a sum of diminishing returns.

    Based on this, and knowing the cost of fertiliser and the sales price for grain, we can calculate the breakeven return (BER) for crops.

    Using Teagasc calculations, where CAN is €620/t and grain can be sold for €200/t, growers can apply 33kg/ha less nitrogen to crops (wheat or barley) and achieve a similar margin.

    Where grain rises to €220/t, growers can use 27kg/ha less nitrogen and still achieve a similar margin.

    Given the projected cost of nitrogen and the sales value of grain, reducing nitrogen will be profitable for most growers.

    Organic manures

    Where growers can get organic manures and maximise the embedded nitrogen then significant savings can be made. There are also savings in P and K contained in slurries.

    The value of slurries are discussed elsewhere in this supplement. For example, a grower applying good-quality cattle slurry 33m3/ha (3,000 gallons/ac) to 20ha (50ac) can save €6,000 on chemical fertiliser when the costs of N, P and K are accounted for (not including the costs of slurry spreading).

    Changing from CAN to protected urea

    Changing from CAN to protected urea can help to marginally reduce emissions on a plough-based system. Research shows some reductions are possible but other considerations such as achieving the correct spread width (out to 24m or beyond) may be more problematic. Examine the costs differential between CAN and urea as there appears to be a significant difference emerging this year.