UK farming’s ambitious goal of reaching net zero by 2040 is going to require some changes in arable farm practices and a willingness to think differently about resources if emissions are to fall.

The top three actions – changing farm practices, increasing productivity and making better use of inputs and resources – can all make a significant difference.

It allows farms to aim to reduce their impact while maintaining productivity.

See also: 6 soil carbon schemes for farmers to consider

Of the three main greenhouse gases (GHGs) associated with the farming industry, arable farming activities are most closely associated with two of them – nitrous oxide and carbon dioxide.

Nitrous oxide arises from nitrogen fertiliser production and application, while carbon dioxide comes mainly from fuel use and field operations.

The other GHG that is attributed to farming – methane – is only relevant to arable farms that are importing manures.

Starting point

Any farm business that wants to start to reduce GHG emissions must understand what the current on-farm situation is and what data is available.

This means farms can understand their starting position and the potential to reduce emissions.

While it may initially add to the office work burden, carrying out a carbon footprinting exercise gives a baseline and can then form a foundation for decision-making, allowing appropriate action to be taken.

As Emma Adams, senior farm carbon and soils adviser at Farm Carbon Toolkit, explains, there is mounting pressure on farmers from the supply chain to know what the carbon footprint of their business is, but there are also compelling internal reasons for doing so.

“Completing the process will give you a position of knowledge and make it possible to identify the hotspots for emissions, which are a good place to focus when making reductions,” she says.

“There are free online tools available that will help you to carry out the exercise. You don’t have to spend lots to establish where you are at the moment and identify if any changes in practice need to be made.”

She adds that the on-farm elements that have a high carbon cost tend to be expensive, such as fuel and fertiliser, so giving them attention will bring further benefits to the farm.

“That is why maximising the efficiency of resources used is a big part of improving your carbon footprint,” she points out.

“By focusing on carbon, building resilience into farming systems and improving resource efficiency, you can maximise productivity and minimise waste.”

Fertiliser

Nitrogen fertiliser is one of the biggest culprits when it comes to GHG emissions from arable farms, as nitrous oxide emissions arise from its production and use.

A very potent GHG, nitrous oxide comes from fertiliser use and attributes about 50% to the manufacturing process and 50% to its use.

The gas is released during spreading and when on the field, through processes such as volatilisation, leaching and direct loss.

It is a priority area for the industry and one that fertiliser manufacturers are addressing.

For instance, Yara has announced it intends to use green ammonia in carbon-neutral fertiliser products, the raw materials for which will be obtained using carbon dioxide-free energy sources rather than fossil fuels.

Until there’s been more progress, there are several actions that growers can adopt to reduce their reliance on nitrogen fertiliser.

However, they may also need to set themselves an overall fertiliser reduction target, says Ms Adams.

“Improving soil health, incorporating cover crops, widening the rotation and using organic sources of nitrogen are all helpful and should be part of the plan.

“Nitrogen fertiliser often makes a large contribution to the emissions of an arable farm.

“If you are reducing your use of inputs – either through better practice or technology – your emissions will fall. So too will the financial overhead.”

Other actions that can include the sourcing of fertiliser products – with those coming from the UK or Europe usually having a lower emissions factor than product coming from China, for example.

Inhibitors, used to slow the conversion of ammonium to nitrate, have a role with urea products and help to improve nutrient use efficiency (NUE), which remains low with many granular fertiliser products.

“The standard figure for NUE from granular products is 60%,” says Ms Adams. “So we know that 40% is being lost at the outset and we need to consider how to minimise these losses.”

Good practice may be boring but it is effective. “It’s about putting on the right product, at the right time and in the right place.

“Given the very high cost of many fertilisers, it makes sense to apply it with accuracy, when the weather and plant growth is going to maximise uptake of the product.”

Phosphorus and potassium fertilisers do not have the same level of nitrous oxide emissions associated with their use but do have a cost in terms of mining and hauling.

“There’s a much lower footprint with an organic source of these nutrients, so the use of muck, other organic fertility sources, or improving the uptake of existing nutrient stocks through methods such as cover cropping can help.”

Fuel

Fuel use makes a large contribution to emissions on a volume basis, although the resulting carbon dioxide produced from its use is less polluting than nitrous oxide.

As far as savings are concerned, there are some easy ones, says Ms Adams, who notes that the technology exists to track fuel use in real-time.

“One of the things that can make a huge difference is to look at how long tractors spend idling,” she says. “The figures will shock you, but they are easily reduced.”

The fuel use per hectare figure is one of the KPIs on Farm Carbon Toolkit’s calculator, so it’s easy to track how it’s changed.

“When looking at actions to reduce emissions, aiming to cut fuel use by 10-15% is a great place to start.”

Cultivations policy should also come under scrutiny, not just for the carbon losses that can arise from soil disturbance and reductions in organic matter, but also from wearing parts.

No-till will not suit every farm situation but does offer useful fuel reductions and soil carbon benefits.

“Arable farming involves a number of passes, some of which could be eliminated or combined  – particularly if input use reduction is the aim.

“Harvest is another hotspot when it comes to fuel use, minimising the time machinery is left idle on the headland or in the yard can save a lot of fuel.

“Each year is different but it is also worth considering the fuel use associated with grain drying.”

At current fuel prices, growers should do the calculations to see whether its cheaper to buy more fuel and increase emissions or to take a moisture penalty, she says.

Soil

For most arable farmers, the goal must be to have a balanced farming system that can still be highly productive, as well as sustainable.

“Look after your soils and minimise any damage that’s done to them,” recommends Ms Adams.

“Recognise that from time to time they can still be a source of carbon emissions, as all systems tend to have periods of decline.

“If the organic matter and, consequently the amount of carbon stored within the soil profile, is decreasing over time, this will be counted as an emission on your carbon footprint.”

Soils represent a huge opportunity for sequestration through capturing and storing carbon from the atmosphere.

However, focusing on soil health and quality will bring agronomic benefits to the farming system, through processes such as nutrient cycling, water storage and overall fertility.

“When measuring your soil organic matter content, the actual figure is less important than the direction of travel. If it’s going up, that’s great,” says Ms Adams. “If you look after your soil, it will look after you.”

Other areas for arable farmers to exploit when it comes to reducing GHGs include renewable energy, woodlands and diverse rotations.

“Opportunities to increase sequestration will vary according to the site, but the goal is to get the system in balance, so that emissions and sequestration are equal,” she says.

Transition Farmer Philip Vickers

A carbon footprinting exercise carried out before Philip Vickers became farm manager at Raby Estate in County Durham.

It confirmed that nitrogen fertiliser was the main culprit in terms of the farm’s total greenhouse gas emissions.

© Raby Estates

Given the nitrous oxide emissions associated with its production and application, Mr Vickers has plenty of ideas about how to reduce the estate’s reliance on bagged nitrogen and has already brought application rates down and made use of alternatives.

“Reductions are achievable,” he says. “This year, we used the lowest ever rate of nitrogen on our oilseed rape but achieved the highest yields.

“We may have mined some soil reserves in such a dry winter, but it showed that there is scope.”

Likewise, the estate’s 2022 spring barley crop received just 80kg/ha of nitrogen, with organic manures also being used to supply some of its nutrient requirements.

While he admits that the desire to save fertiliser stocks for next year helped with some of the decisions, Mr Vickers suspects that over-application may have featured in the past when fertiliser prices were lower.

As a result, close monitoring and targeting of nitrogen fertiliser is now carried out to ensure that it is matched to crop need and applied in optimum conditions.

“We know that the efficiency of nitrogen fertiliser use isn’t very good across the industry, so everything that we can do to improve this figure is worthwhile – especially given current prices and availability issues.”

For the first time ever, manures were applied to growing winter wheat and barley crops in the spring of 2022.

“Having never done this before, the idea filled me with dread,” he recalls.

“We used an experienced contractor with very big kit, and although we could see where he had been, there was a yield benefit.”

Getting hold of manures in 2023 could be a problem, he anticipates, as the avian flu outbreak has affected the supply of poultry manures and others are worth much more than they used to be.

Otherwise, he is keen to investigate composting as another way of supplying nutrients and is interested to hear from other farmers in the north of the country having success with the technique.

In terms of other greenhouse gases, fuel use has come down with the move to a regenerative system and cultivations have reduced, helping to lower carbon dioxide emissions.

“We know where we should be targeting our efforts, so we can continue to make progress with emissions and reaching net zero,” Mr Vickers adds.