This article was written by Andrew Ross.
Recently we had two Highbridge Community Farm soil samples analysed by the Soil Association. The samples came from plots 3&4 which have been practicing minimum dig and planting winter cover crops for two years now, so the soil here should be among the best on the farm.
What was in the samples?
The samples showed that soil organic matter was 11.2% on plot 3 and 12.6% on plot 4.
Soil organic matter is a complex mixture of all organic material found in the soil including living components (plant roots and microorganisms) and dead components (leaf litter and humic substances). It increases the soil water-holding capacity and provides a slow release source of energy for microorganisms which increases the cycling of nutrients within the soil.
These samples suggested that the total organic carbon stock in tonnes of carbon per hectare of land to a depth of 30 cm would be in the range of 199-212 tonnes for this part of the farm.
More SOIL oRGANIC MATTER MEANS BETTER GROWING CONDITIONS
The implication of this analysis is that our soil organic matter has risen from around 4% when we took on the land in 2010 to 12% in 2021.
This organic matter acts like a sponge and the top 30 cm of our soil now holds around 90 litres of water per square metre when it is at field capacity (full of water- but not waterlogged) instead of about 45 litres if there was no organic matter present. There are also many more nutrients available for our crops to grow well.
Plus, OUR plants REMOVEd carbon dioxide from the atmosphere
As well as improving our soil considerably we have effectively removed carbon dioxide from the atmosphere as the plants photosynthesised and made the atmospheric carbon dioxide into plant biomass which was then recycled and added to the soil as compost (along with manure). This is known as soil carbon sequestration.
beware of short cuts
Recently I attended an online Soil Association Symposium where I learned that companies are concerned about their contributions of carbon dioxide to the atmosphere because this is promoting global warming.
In their desire to appear “green” or environmentally-friendly, some companies are offsetting their CO2 (carbon dioxide) production by paying others to plant trees, restore wetland peat bogs (which are great for sequestering carbon) and even paying farmers to sequester carbon in their fields. One figure quoted was a payment to a farmer of £23 a ton for each ton of carbon sequestered.
The danger of this system of carbon offsetting is that it can become like the selling of Indulgences by the Roman Catholic church during the Middle Ages which allowed sinners to go on sinning. We don’t want to see companies paying money for carbon sequestration but being allowed to go on polluting the environment with chemicals or even carbon dioxide. Nor do we want to see woodland owners taking the money to plant trees or farmers taking the money to sequester soil, only for them to plough up the land again in 10 years time!
We live in a complicated world.