What happens when you try to train 100 Finnish farmers carbon management?

What happens when you try to train 100 Finnish farmers in the ninja arts of carbon management plans for their farms—the subtle yet essential tweaks to farming practices to put carbon back into the soil rather than mining out every last ounce? 

Funny enough, researchers from the Centre for Sustainable Production and Consumption, Finnish Environment Institute, Helsinki, asked such a question in 2018. 

Presumably motivated by similar worries about the loss of soil organic carbon that pepper several posts on sustainably FED, the Fins completed research for the people by the people exercise to answer the question.

• More carbon in the soil than in the atmosphere
• You really need to know this
• Fixing climate with soil carbon has a big bonus
• Textile waste is useful, so we need to recycle it

At a workshop, volunteer farmers, most early adopters of novel approaches and knew what they were doing around crop rotations, field operations, fertilization and animal husbandry, were given a crash course in the science of soil carbon and then signed up to 

• select a plot on their farm for carbon-farming experiments 
• take soil samples at the start of the study and after five years
• make a 5-year carbon-farming plan (Plan) for the plot

As part of the carbon-farming plan to increase the carbon stock of a chosen field plot (roughly 3 ha size) over five years, the farmers were asked to choose a “carbon pathway” from options that

1. increase photosynthesis during crop growth
2. Lengthen the photosynthesis period (winter sown crops, leys and cover crops) 
3. improve soil biological activity; 
4. improve soil structure and rooting depth and 
5. managing organic soils for carbon storage. 

Each Carbon Farming Plan consisted of a crop rotation, the planned use of cover crops, organic amendments and specific management actions (tillage, seed mixtures, fertilizer) to increase soil carbon. 

This is what we would expect to happen if farmers are told about soil carbon by scientists. From experience, they would already understand the benefits of carbon-rich soil and quickly adapt the science concepts to their operations.

Almost half of the 100 farmers chose to improve soil structure (49), followed by increasing soil biological activity (25), increasing photosynthesis duration (18), increasing photosynthesis intensity (13) and maintaining C-stock on organic soils (2).

Adaptation focused on cover crops, importing nutrient-rich soil amendments, subsoiling and ley diversity. Less popular was the addition of nutrient-poor material, including leys in monocropping rotations, improved grazing practices, and maintaining C-stock on organic soils and agroforestry. 

Given a choice, farmers were adaptive even if they kept changes within their frame of reference.

Farmers preferred to gain carbon from internal sources. Even though half the farmers planned to add manure or soil amendments, only a third of this carbon input came from outside the farm. 

The researchers then used some basic carbon accounting to predict the consequences of the farmer’s plans. What they found looked like this, where anything above the red line is good

Planned additions and removals from soil organic carbon pools in the 105 carbon farming plans. Points above the 1:1 line have a positive carbon balance. Trial fields (filled), control fields (unfilled).  Source: Mattila, T. J., Hagelberg, E., Söderlund, S., & Joona, J. (2022). How farmers approach soil carbon sequestration? Lessons learned from 105 carbon-farming plans. Soil and Tillage Research, 215, 105204

But here is the thing.

The farmers were asked to maintain a control plot for comparison. The predicted difference between carbon storage with the Carbon Farming Plan and on the control field was small, with a predicted difference of 0.14% difference in SOM concentrations in 5 years. Only 16% of the Carbon Farming Plans would have resulted in > 0.5% difference in SOM change between carbon farming and control plots. 

As the measurement of a difference of 1 t C/ha in SOC stock requires hundreds of samples, many planned differences are below current detection limits and would not be detected by field sampling.

The researchers grappled with the lack of correlation between the amount of carbon in the soil currently and the planned addition of carbon.

They suspected that the farmers were either not aware of the organic matter content in their soil, did not think of carbon balances when planning or lacked patience and added much more carbon than needed for maintenance. Perhaps, they thought, farmers are not systems thinkers.

Turns out most scientists aren’t systems folk either.

What sustainably FED suggests

This kind of science is bold and risky. A guided citizen science study in a short-term paired plot design where the desired result – an increase in soil carbon – is hard to measure and attribute. Note that some control fields (open circles on the graph) are above the red line. 

There is a risk to the adoption of any practice change if the outcome is uncertain. It is awkward if the gain is present but undetectable with current measurement tools.

In the aggregate, the planned additions and removals from soil organic carbon pools chosen by the Finnish farmers were positive—more C input than estimated decomposition, so carbon should accumulate in the soil overall.

But if this is not detectable at the farm scale, the benefit is collective, not individual. This makes it hard to reward farmers for their soil carbon gains based on actual sequestration, the preferred method of the carbon market mechanisms, even if on average, the carbon farming plans worked.

We think these results suggest the activity gets the reward and not the actual sequestration.

Science source

Mattila, T. J., Hagelberg, E., Söderlund, S., & Joona, J. (2022). How farmers approach soil carbon sequestration? Lessons learned from 105 carbon-farming plans. Soil and Tillage Research, 215, 105204

Hero image from photo by David Mark from Pixabay