Learning to lower nitrous oxide levels

Nitrous oxide is the most significant of all the greenhouse gases released by UK agriculture.

Although only 6% of all UK greenhouse gases are in the form of nitrous oxide (N2O), two-thirds originate from agricultural production.

Now an initiative is being launched to determine how British farmers can reduce their emissions of the gas which is the most damaging of all greenhouse gases on a tonne-for-tonne basis.

Co-ordinator Roger Sylvester-Bradley of ADAS explains that current advice is based on work by the Intergovernmental Panel on Climate Change and applies to all temperate regions and not specifically the UK. The initiative is seeking funding partners. Fertiliser manufacturer GrowHow is already supporting the project.

Prof Sylvester-Bradley says there are areas that need to be examined, including:

Improved estimates of nitrous oxide emissions associated with production of the major UK arable crops, in anticipation of carbon accounting at the field and farm scale

Quantifying with N2O emissions associated fertiliser applications, soil conditions and composition of crop residues, crop species and growing conditions (eg regional climate, soil type)

The development of specific UK systems that allow for the management of N2O emissions

The development of strategies for minimising N2O emissions from UK field cropping and in the first instance to develop best practices for optimising GHG savings from biofuel production, through choice of genotype, agronomy and rotation.

Prof Sylvester-Bradley says that some people might imagine that by not applying artificial nitrogen fertilisers the problems of nitrous oxide emissions could be solved.

“But fertilisers are not the only source of emissions and if no fertiliser was applied, there would be a deficit of 7-8m tonnes of UK wheat alone that would have to be grown elsewhere, possibly on virgin land that would need ploughing up, releasing a lot more carbon dioxide.”

Transparent carbon footprints

Declarations of the carbon footprints of agricultural products are likely to become commonplace.

Sainsbury’s announced that it has been working with the Carbon Trust and nutrition company AB Agri to carbon-audit all 325 of its Dairy Development Group producers. An initial survey has been conducted taking into account electricity, fuel and machinery use, and manure storage. Further audits will take place over the next three years.

Areas for improvement that have already been identified include use of manure and fertiliser, feed efficiency and stocking rates. Some of the highest yielding farms were not the most carbon intensive. It is estimated that implementing improvements will reduce emissions by 10% a year.

Euan Murray of the Carbon Trust says that implementing carbon saving measures makes a farm more efficient.

He says that carbon accounting techniques are developing all the time allowing farmers to measure their environmental impact.

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