In its white paper, Net Zero by 2040, the NFU outlines a more ambitious target for agriculture, aiming to achieve carbon neutrality 10 years faster than the UK as a whole. By Marianne Curtis and Adam Clarke.
Speaking at the Association of Independent Crop Consultants (AICC) conference near Towcester, NFU climate change adviser Ceris Jones said to do this, the industry had to move much faster and further than ever before.
“It’s going to be about reducing our own emissions and doing what other sectors of the economy can’t do – taking carbon dioxide out of the atmosphere and storing it,” she said.
The way the NFU hopes the industry will achieve net zero is through its ‘three pillars’, which include improving production efficiency and reducing emissions, capturing carbon in farmland, and boosting agriculture’s contribution to renewable energy generation and the bioeconomy.
At the same conference, Dr Alastair Leake, director of policy at the Game and Wildlife Conservation Trust (GWCT), shed some light on the practical implications of reducing greenhouse gas emissions for arable farmers.
He pointed out that nitrogen fertiliser is by far the biggest culprit in terms of greenhouse gas emissions in the crop production sector, with 50% of N applied contributing 80-90% of wheat yield.
This means the remaining 50% contributes to just 10% of the yield and any losses have the potential to pollute, so improving nitrogen efficiency would provide big gains in terms of hitting emissions and environmental targets.
Dr Leake said: “Is there somewhere I would call the economic and environmental optimum [for nitrogen use]? We do tend to focus on the yield optimum, but what about the environmental one as well?”
He also pointed out that some of the UK’s most fertile soils – such as those in the fens across East Anglia – are being intensively farmed and slowly shrinking, releasing large amounts of carbon in the process.
With no plan in place to protect it, this is likely to continue, and a ‘restorative’ phase is needed in crop rotations – ideally establishing grass and clover leys – to capture carbon and put it back into soil.
“What I would like to see is farmers on Grade 1 peatland put grass leys in to restore fertility, stabilise soil and be paid to do it.
“We have had no problem in paying farmers to put 15-20% of their land into set-aside, so we should have no problem in paying farmers to put 15-20% of their land into soil restoration measures,” said Dr Leake.
In addition, reducing tillage and horsepower requirements on-farm will reduce carbon losses associated with practices such as ploughing and the diesel burned in the process of turning soil over.
However, this perception does need to be treated with caution in relation to overall greenhouse gas release, as demonstrated by work carried out by GWCT on gaseous emissions from the soil under different tillage regimes.
Interestingly, while ploughing did cause higher levels of CO2 emissions than minimum- or zero-tillage, the effect of cultivation on nitrous oxide emissions from the soil is the opposite, with soils under zero-tillage being the worst culprits.
“This is often because these soils are tighter and, therefore, more likely to be [more] anaerobic,” explained Dr Leake.
He added that if the nitrous oxide emissions data from the trial are turned into a carbon dioxide equivalent, there is very little net difference between the control and plough-based treatment.
This is important because there are calls for no-till farmers to be paid for carbon credits.
Although this may be a good idea for carbon capture, it might be outweighed in the context of greenhouse gas emissions by nitrous oxide.
“That would not necessarily be public money for public goods, so we have to be careful we are paying for the right things,” said Dr Leake.
Organic matter is also an area where there is a ploughing versus no-till debate, with the latter often said to the be the best system to build organic matter in soils.
While there are clearly many benefits from practising no-till instead of ploughing, including boosting organic carbon levels in topsoil, its overall advantage in this regard is questioned by another GWCT study.
Organic matter levels were tested at various depths down to 20cm in a no-till and plough-based system at the Allerton Project, Leicestershire, and a neighbouring farm.
Predictably, there was a higher concentration of organic matter in the top 10cm of a no-till system, then levels drop deeper down the soil profile.
However, in the ploughed soil there was a higher concentration down at 20cm, where residue had been buried each year.
“The overall difference between the two systems is marginal and I was pleased to see a report produced for Defra by Rothamsted [Research] and ADAS indicated that indeed was the case,” said Dr Leake.
He also highlighted the well-publicised benefits of cover crops in capturing nutrients and keeping them in the arable system, improving nitrogen use efficiency and adding carbon to the soil through their roots.
Similarly, agroforestry – where trees and cropping or grassland coexist – and planting or improving hedgerows and suitable woodland management can also help capture more carbon around the farm.
However, he warned farmers should not necessarily get too hung up on the idea of capturing carbon, as many of the practices which will help meet emissions targets also provide a much wider benefit.
For example, cover crops have agronomic benefits and, along with trees and hedgerows, help promote biodiversity. Switching to zero-till systems can also increase soil biology, such as earthworms, and increase production efficiency, not just reduce CO2 losses.
“I’m very keen we avoid getting utterly focused on a low or no carbon agenda and forget we have many other things we have to do in terms of economics, wildlife and biodiversity, too,” he added.
Other ways of reducing the farm carbon footprint include producing fuel on site for woodchip burners, investing in solar panels for electricity supply and using natural or sustainable building materials for improving infrastructure.
Specific examples at the Allerton Project – led by Dr Leake – are its use of straw to insulate new buildings, and the car park constructed from a material made from recycled silage wrap, instead of laying concrete which has a high energy requirement.
“The second use plastic will take a lorry up to 30 tonnes and it is permeable, so [water] doesn’t run off and flood the village next door – it soaks in.
“And we’ve made even better use of it by sowing it with wildflowers and the bees can make use of it in the summertime.”