NFU climate change specialists, Jonathan Scurlock and Ceris Jones discussed the science behind N2O emissions from agriculture and took questions from members.
Attendees heard how fertiliser use efficiency is key to minimising these emissions. Nutrient management planning and precision agriculture can reduce N2O emissions by ensuring that nitrogen is only applied according to crop or pasture need.
Alternative approaches to fertiliser application were discussed, such as foliar application of nitrogen which could improve efficiency of uptake by avoiding nitrogen entering the soil.
However, unexpected rain and chemical leaf scorching are barriers to be overcome.
What is N2O?
N2O is a long-lived gas which accounts for approximately 32% of UK agricultural emissions.
It is an unavoidable part of food production, produced when nitrogen is broken down by soil microbes. N2O losses can be particularly bad from wet and compacted soils.
It was agreed that scientific developments are going to be crucial in providing solutions, with more research needed into technologies such as biochar, inoculating seeds with nitrogen-fixing microbes and breeding for improved nitrogen use efficiency.
NFU Deputy President Tom Bradshaw said: “For the majority of our members this is about driving efficiencies. What’s good for reducing N2O emissions is good for your bottom line – it’s about building that business resilience.
“Whether that is about driving animal health and welfare or using inhibited nitrogen, it should be a net gain for the business rather than a cost for the business.”
Q: Will nitrification inhibitors damage soil microbiology and overall soil health?
A: It is a valid concern that at present, nitrification inhibitors are not universally effective, and they may work better in some soils/environments than others. This needs further research.
Q: How realistic is the opportunity to improve foliar nitrogen uptake, particularly for cereals?
A: The NFU’s net zero Science Advisory Panel believes that when compared with nitrogen uptake from the soil, foliar N application has significant potential to increase the efficiency and reduce nitrogen losses. Breeding for enhanced foliar absorption of N may even be a desirable trait in the future. Many companies are working on this presently, as well as other innovations such as seeds pre-inoculated with N-fixing microbes, but these developments are not commercially available at the moment.
Q: Does covering up a slurry store make any difference to your N2O emissions?
A: Slurry covers are proven to be beneficial for reducing ammonia emissions but not so much for N2O, and even this benefit depends on the type of slurry cover.
Q: What is the current progress being made on treating slurry to reduce emissions?
A: There are a number of new processes in development (such as N2Applied and CCm Technologies) that treat slurry or digestate, reducing ammonia emissions and producing a concentrated organic fertiliser. The overall objective is to upgrade raw manures/slurries as natural sources of plant nutrients, making them easier, cheaper, and more effective to apply, at a time of rising prices for synthetic fertilisers. Overall, this circular approach to farming is hugely beneficial to minimise the need for imported nutrients.
Q: What are the overall net impacts of N2O when putting slurry through an AD (Anaerobic Digestion) plant?
A: AD is an enabling technology for better nutrient management through measuring the nutrients in order to make the best use of them and therefore helping to minimise N2O losses.
Q: What work has been done on digestate in general, especially higher nitrogen content digestate?
A: Defra currently takes a rather precautionary approach to managing slurry in AD plants, seeing the technology as a risk multiplier that may increase ammonia emissions by making nutrients more readily available in digestate. We would rather they saw AD as an enabling technology for managing nutrients more efficiently and minimising unwanted losses as ammonia or N2O.
Q: What research is being done to help us with N2O emissions and how is it/could it be funded?
A: Government funded some research on nitrification inhibitors about 10 years ago, but there has been little since. The NFU has called for policy incentives to better evaluate effectiveness of controlled release fertilisers and nitrification inhibitors under real-world conditions, but we agree that more independent advice (e.g. from AHDB) is needed to give farmers confidence in new products.
Q: What role does the NFU have in regard to managing N2O emissions?
A: Our job is to bring rigour to the evidence being brought forward. NFU members cannot be put on the wrong side of this, by thinking they are doing something right but spending money on something that doesn’t actually work. Independent research review is essential to determine what is factual and effective.
Q: How do N2O emissions vary between soya protein feed and soya replacements like PAP (Processed Animal Protein) and insect protein, given that the environmental impact of soya is so important for animal feed?
A: Politically, soya is a subject that is not going to go away. We need to stay ahead of this topic, and the NFU is having conversations about insect protein, PAP and other substitutes, given the likely drive by supply chains to reduce reliance on soya within all feed rations. The main greenhouse gas impact of soya feed in poultry it through associated deforestation and loss of soil carbon, depending upon where it is grown, rather than N2O emissions.
Q: Should regulation of fertiliser ammonia emissions be delayed until independent research proves the economic value of protected urea?
A: Farmers and growers need to demonstrate as an industry that we can minimise our ammonia emissions ourselves, rather than being regulated by government. Maintaining access to untreated urea is crucial for competition with ammonium nitrate, so we have to move ahead with ’Option 4’ which we have delayed to 2024, a self-regulation approach that limits our use of unprotected urea mostly to colder months – and research on the value of protected/inhibited urea can continue alongside that.
Q: What can we do to stop diffuse pollution of nitrogen into water courses, hedgerows, etc?
A: It is down to every one of us to maximise the efficiency of our use of expensive nutrients around field margins, whether spreading organic solids or applying inorganic liquid fertilisers. Buffer strips also intercept nutrients, reducing the concentration of nitrogen in surface water runoff.