Carbon for farmers: Why you need to get a soil carbon baseline now
Everything you need to know about getting a high integrity soil carbon baseline that will stand the test of time.
Climate change is now an inevitable feature of the conversation around UK farming as the government strives to achieve ‘net zero’ emissions of greenhouse gases by 2050.
Although farming releases greenhouse gases, farmland can also remove carbon dioxide from the atmosphere. The amount of carbon removed can be sold in the form of carbon credits.
In this first our series of articles explaining carbon for farmers, Regenerate Outcomes’ Chief Scientific Officer and sheep and beef farmer Dr Matt Jordon introduces some key concepts and terminology to help farmers navigate all things carbon.
The importance of getting a soil carbon baseline now
There is much nervousness in the farming community about carbon markets and a lot of people are advising farmers not to sell carbon credits from your farm.
However, farmers should not let this put them off getting a measured soil carbon stock baseline in place.
Once you have a baseline, you can capture the value of your future management and actions, and track and evidence the improvements you’re making over time.
Matt Jordon, Regenerate Outcomes Chief Scientific Officer
Many farmers think that by doing nothing, you’re keeping your options open for the future.
While this is to some extent true, it also means you’re not recording the carbon you might be sequestering now.
If you only baselined in five years time, you would never be able to count the carbon you sequestered between now and then.
Broadly speaking, getting a baseline in place opens up more options for you in the future rather than reducing them.
“Getting a baseline in place opens up more options for you in the future rather than reducing them. ”
If done correctly or through a suitable programme, getting a baseline doesn’t need to commit you to entering the carbon market or selling carbon credits from your farm.
However, it does give you these options in the future, as well as the ability to make claims about your own business or use them in your food supply chain.
Don’t waste money on an inadequate baseline
If you’re going to invest in a baseline, you should make sure the data you’re getting will be fit for purpose.
Simply having a Loss on Ignition soil organic matter percentage for each field (as required by SAM1 in the English SFI) would not qualify as a soil carbon stock baseline.
Make sure that enough samples are taken and the sampling is done in a rigorous way that will stand the test of time.
Sampling depth is important; higher quality verification schemes typically don’t accept sampling down to only 30 cm or less.
Also make sure you’re getting the right analyses done; you need both soil carbon concentration and bulk density to calculate soil carbon stocks.
Keep the intended end-use in mind; for example some verification standards set sampling requirements and won’t accept baselining to a lower standard.
Unfortunately, some farmers and organisations spend lots of money on soil testing thinking that they’re getting a baseline, then find they can’t use it for their desired purpose because the data isn’t up to scratch.
It typically makes most sense to get a baseline which follows an international verification standard, so that you can be confident of getting the value from your baseline in the future.
Agricarbon carry out high integrity soil carbon baselining and measurement for Regenerate Outcomes
Many farmers find it beneficial to work with a trusted partner like Regenerate Outcomes who can facilitate baselining to a very high standard that is compatible with verification schemes and keeps all options open.
However, bear in mind that some other carbon programmes don’t actually require baseline sampling and just rely on satellites or models to predict soil carbon. Don’t think that by joining any carbon programme you will automatically get a measured baseline.
Getting your first soil carbon baseline
A soil carbon baseline represents the starting point from which future change is measured.
There are two key measurements needed from a soil sample to calculate the stock: the percentage soil carbon content and bulk density (measured in grams per cubic centimetre). Combined with the sampling depth, this gives the soil organic carbon stock.
Soil organic carbon percentage is most reliably measured using a technique called Dumas, in a purpose-built analyser. Dumas analysers heat up the soil sample and measure the amount of carbon dioxide released, corresponding to the starting carbon content of the sample.
The Loss On Ignition method is less reliable, as this is based on weighing the sample, burning the carbon off, then weighing it again to find the difference.
In terms of soil sampling to measure soil carbon stocks, the gold standard is to measure carbon content and bulk density from the same sample.
An Agricarbon soil core
Other sampling approaches may take separate samples in close proximity for carbon and density, but this introduces additional variation and so uncertainty.
Some sampling approaches pull and analyse individual cores, so the number of lab results matches the number of cores taken.
Other sampling approaches take what is known as a composite sample, where several cores are pulled and combined into one sample which is well mixed then analysed once.
This is the standard approach for field-level sampling for common soil nutrients (e.g. P, K, pH etc.) that most farmers will be familiar with, and is useful for management purposes.
However, for soil carbon stock baselining, while this gives a similar average result to individual core analysis, it risks misrepresenting the variation in carbon stocks across a field or farm.
Building carbon stocks from a baseline
Because change in soil carbon stocks is relatively slow, it is difficult to detect meaningful changes if you sample every year. Sampling every five years or so is a good compromise between frequent monitoring and ability to observe change.
Over five years, let’s assume your carbon stock increased by two tonnes, from 72 to 74 tonnes of carbon per hectare.
For comparison, this would correspond to approximately 0.1% increase in soil organic matter. Two tonnes of soil carbon represents 7.2 tonnes of carbon dioxide equivalent, so over the five years this would be a sequestration rate of 1.44 tonnes of carbon dioxide equivalent per hectare per year.
One carbon credit represents one tonne of carbon dioxide equivalent. Therefore, this would be equal to 1.44 carbon credits per ha per year.
Here, you can see how soil organic matter translates through to soil carbon stocks, and how a change in stocks over time gives a rate of sequestration or a number of carbon credits per hectare per year.
Carbon baselining and measurement at no upfront cost
Regenerate Outcomes provides rigorous soil carbon baselining and measurement.
Our mentoring team work with farmers to build productive soil by increasing organic matter. The increase can then be used to generate carbon credits which you can retain or sell for additional income.
We work with Agricarbon to measure increases in soil carbon. Agricarbon base their measurements on physical samples from your farm. Samples are completed at a depth to meet the demands of higher quality verification schemes.
This means the credits can attract a higher premium than those generated in other schemes.
Download our programme handbook to find out more.