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A number of key issues that the local dairy sector must address in the future are set out in the third EU Sustainable Fact Book, published by the Dairy Council NI (DCNI).
In the introduction, written by DCNI chief executive Mike Johnson, he focuses on the pressure to reduce greenhouse gas emissions, with NI expected to cut carbon emissions by at least 82% by 2050 as part of the overall UK target to be net zero carbon by that date.
But, he also points out sustainability isn’t just about the environment, with dairy farming providing an important source of nutrients for humans, as well as income generation within rural communities.
As a result, Johnson argues that it is “imperative” that policy decisions are based on evidence, and designed in partnership with the sector.
Methane
One area where this is perhaps most pressing at present is in how methane emitted by ruminant livestock is assessed in greenhouse gas accounting systems. In NI, estimates suggest that methane accounts for up to 65% of greenhouse gases from agriculture.
However, in his contribution to the DCNI publication, air quality specialist Professor Frank Mitloehner from the University of California, notes that the current international accounting systems do not allow for the fact that methane has a short life of around 10 years.
Methane breaks down into carbon dioxide (CO2) and water vapour, with this CO2 taken up by plants, which are subsequently eaten by animals. “This is recycled carbon, that is not adding additional carbon to the atmosphere,” notes Mitloehner.
By contrast, burning a fossil fuel such as oil, coal and gas adds new CO2 to the atmosphere, which is leading to global warming “at an alarming rate,” he points out.
So on the one hand, agriculture’s contribution to overall emissions is exaggerated. But it is also the case that if farmers can reduce methane emissions (eg. by using feed additives), it will immediately have a cooling effect on the planet, as more methane is being destroyed (after 10 years) than is being emitted.
“The dairy sector can play a role in keeping climate warming at bay, providing we succeed in reducing methane,” concludes Mithloehner.
Heifer rearing
Among the other issues explored in the DCNI report is the impact on greenhouse gas emissions from calving heifers at 24 months.
Analysis of APHIS data in 2016 suggested that the average age at first calving for dairy heifers in NI was 27.5 months. Reducing this to 24 months could lower overall dairy emissions by 7%.
Water quality
However, the future is not just about greenhouse gas emissions, with the pressure on the dairy industry to play its part in improving water and air quality, by making best use of inputs.
The key to ensuring efficient use of slurry and fertiliser is to correct soil pH using lime, and to apply nutrients to match crop needs.
With excess Phosphorus (P) run-off a major cause of lower water quality in NI, P-containing fertiliser should not be spread on land above the optimum index of 2+, and slurry should ideally be targeted at low index fields.
On many dairy farms in NI, the major source of P is via concentrate feed, not fertiliser.
The DCNI report notes that CAFRE benchmarking figures show that some farms can produce yields of 8,000l using 1.7t concentrate, while others are feeding up to 4t for the same output of milk.
High feed levels can lead to a surplus of P, which increases the risk that it eventually ends up washed into waterways. And if diets are too high in protein, this can lead to low N use efficiency, which is ultimately lost as ammonia.
On many farms, the key to improving concentrate use efficiency is to increase the quality of forage offered, which will indirectly benefit the environment and ultimately, the bottom line.
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