RSPB Volunteer, Alex Mackenzie, writes a summary of Hope Farm’s Technical Webinar on Carbon-friendly farming, chaired by Dr Rob Field. It featured insights from Dr Jenny Bussell, Soil Scientist at the Allerton Project; Sophie Arnold, Hope Farm Assistant Manager; and Clara Robinson, Hope Farm project manager.
Why the Focus on Carbon?
Over the past century, human activities such as fossil fuel consumption and land-use changes have caused a surge in atmospheric carbon levels, resulting in climate change. Agriculture is both a culprit and a potential saviour. It significantly contributes to greenhouse gas emissions, yet it could hold the key to mitigating climate change through carbon sequestration and emission reduction strategies. But what does this mean in reality.
Unlocking the Secrets of Soil Carbon at the Allerton Project, Game and Wildlife Conservation Trust: Dr Jenny Bussell
Understanding Soil Health
Soils are vital for sustaining life, regulating water flow, gas exchange, and cycling nutrients essential for plant growth. Soil organic matter (SOM) is crucial in maintaining soil health by enhancing water retention, reducing compaction, and allowing microbes and other soil life to flourish. Approximately 50% of the Earth's biodiversity is estimated to reside in soil.
Soil Carbon and Climate Change Mitigation
SOM, or soil carbon, is important for carbon sequestration because it's about 58% carbon. However, SOM is slow to build, the amount of carbon sequestered is hard to measure, and some carbon needs breaking down to release nutrients for crops to grow. Soil carbon is like a currency for farmers, which is both spent and saved. It exists in two forms: slow or active carbon. Slow carbon takes longer to accumulate and break down and ideally should remain undisturbed. In contrast, active carbon breaks down quickly, providing nutrients for crops. Activities such as cultivation can rapidly release all the soil carbon that took years to build, making it challenging to store carbon in soils for climate change mitigation.
Farming to Improve Soil Organic Matter at the Allerton Project
Increasing soil carbon while maintaining food production isn't a linear process, and carbon expenditure needs to be thought about throughout a full rotation. The goal is to minimise declines and maximise periods of carbon accumulation. For example, while practices like cultivation can reduce soil carbon through disturbance, this can be counterbalanced by growing cover crops for a year to rebuild the carbon store.
At the Allerton project, a demonstration and research farm in Leicestershire, a high-tech gas analyser and low-tech soil sampling methods track the impact of ploughing, disking, and direct drilling on soil carbon. Researchers have found that ploughing causes more disturbance, leading to higher carbon emissions, with all the carbon rapidly released within 2-3 days of ploughing. In contrast, direct drilling results in higher levels of SOM and healthier soil. Despite continually cycling carbon, it releases fewer emissions than ploughing.
Investigating Carbon Farming at RSPB Hope Farm: Sophie Arnold and Clara Robinson
Addressing Climate and Biodiversity Crises
The Paris Agreement mandates limiting temperature rise to 1.5 degrees Celsius, requiring net zero CO2 emissions by 2050. Agriculture is the second largest contributing sector, but unlike other sectors, CO2 is not its predominant emission. Therefore, it’s essential to calculate and understand our farming systems' existing greenhouse gas flux before making changes.
The RSPB's Carbon Farming Project is looking for win-win situations for biodiversity, nature, and the climate. It has three elements: an agroforestry research trial, running three prominent carbon calculator tools on Hope Farm and other farms around the UK, and reviewing these tools.
Agroforestry in the UK
At Hope Farm, we are running a 10-year agroforestry research trial planted in the winter of 2022. Agroforestry may offer numerous potential benefits, including improved air quality, water infiltration, and carbon sequestration. However, it's not commercially common in the UK, and what it can deliver, in reality, is not currently well understood. The trial at Hope Farm involves an 11-hectare field with 8 rows of trees interspersed with 24m cropping alleys. Monitoring encompasses biodiversity, carbon sequestration, CO2 flux, and crop yield compared to a control field. At this stage in the trial, it's too early to draw any conclusions, but the first full year of CO2 flux data is currently being analysed and will be made available as soon as possible.
The Agroforestry trial at RPSB Hope Farm
Using Carbon Calculators
The three carbon calculators on trial are Agrecalc, Cool Farm Tool and Farm Carbon Toolkit. The review revealed a high level of variation in the outputs produced. Divergence in outputs was most pronounced in farms with organic soils and high soya feed levels. Key sources of divergence included crop residues, enteric emissions, embedded emissions, land use inclusion, fertiliser production, manure management, and nitrous oxide emissions. Differences also stemmed from varying system boundaries, data entry requirements, and the incorporation of standardised datasets and emissions factors. However, it's important to remember that all carbon calculators are models and generally perform well - there is no correct answer.
Regarding usability, although the layouts vary across calculators, the information required for the calculations is largely the same. As the calculators develop, there's a need for better definitions and consensus on what should be included in farm-level assessments, including boundaries, covered enterprises, end goals, and financial considerations. Additionally, greater transparency in the confidence of calculator results is needed, including clear assumptions and error ranges.
Summing Up the Reality of Carbon-Friendly Farming: Dr Rob Field
Carbon-friendly farming can range from plot-scale changes in soil management to field-scale initiatives such as agroforestry to combining different approaches and trying to predict the impact on emissions across a whole farm. The big challenge for farming is managing land to balance carbon management with productivity while considering the implications for habitat management and wildlife.
Finally, the variability in outcomes from different carbon calculator tools underscores the importance of selecting a tool that fits one's farm and data management style to track changes within an individual farm rather than trying to make comparisons between farms.
Find the full recording of this webinar and other Hope Farm technical webinars here: https://www.youtube.com/watch?v=vXes5OsA1-k&t=157s