Healthy soil and sustainable growing

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Climate-friendly Farming
The new approach of ‘rich-soil’ farming reveals that correctly managed 
agriculture could help us to turn back the carbon clock.
http://www.resurgence.org/magazine/article2955-Climate-friendly-Farming.html

Putting the many approaches to agriculture into simplistic categories and 
making sweeping generalisations about their merits and faults has led to 
farmers of all kinds feeling that their methods are unfairly criticised. 
There are farmers employing good techniques in every category. As well as 
working harder than many other professions, for low remuneration, most 
farmers care about their work and want to provide the best products and 
maintain their livelihoods for the future. However, pressures including 
competition, prices, perceived need for high productivity, sector policy and 
marketing of agricultural inputs have led to many farm practices that 
‘borrow’ more carbon from the soil each year than they put back.

There is a newly emerging way of looking at farming that recognises good 
techniques being practised on any type of farm. It gives credit where due and 
creates a level playing field for assessing all approaches to farming: 
traditional, mechanised, intensive, organic, biodynamic or permaculture. This 
universal aspect of good farming could perhaps be called ‘rich-soil farming’.

The three major considerations in the assessment of food production are the 
quality and quantity of food produced and the ability to continue production. 
At a biological level, it is soil that produces food, and its production 
capacity can be enhanced or reduced. Typical rich forest soil might be made 
up of approximately 15% air, 15% water, 60% rock and minerals and 10% organic 
matter. Organic matter is decomposed plant matter (humus) and animal life in 
the form of microbes and insects, and is at least 50% carbon. As the rock 
content of soil is stable, and air and water content are affected by organic 
matter, the critical controllable factor that determines food quality, 
quantity and continued productivity is increasing or decreasing its organic 
matter content.

Over 70% of Britain is covered with agricultural land, so the greater part of 
the soil and plant life of this island is controlled by human management. The 
soils of natural oak forests in the UK contain around 10% organic matter but 
in the majority of British agricultural land this has been reduced to an 
average of 3.5% and in some intensively farmed arable land to just 1%. But 
the good news is that while some farming practices decrease soil organic 
matter, others increase it, and a host of recent studies are helping to 
define the effectiveness of different practices.

In my role as designer of the Resurgence Carbon Calculator and a promoter of 
low-carbon lifestyles, I was recently approached by Jonathan Smith of Climate 
Friendly Food (CFF), an organisation dedicated to reducing the climate impact 
of food and farming. Jonathan asked me to work on the development of a new 
carbon calculator for farmers and growers, that takes into account the 
sequestration processes in soil and plant life. He envisaged that the 
farmers’ and growers’ carbon calculator would form the basis of the world’s 
first low-carbon food certification programme, enabling food producers to 
calculate and label the climate impact of their produce and allowing 
consumers to choose products that help mitigate the effects of food 
production on the climate. What neither of us expected was that the carbon 
calculator unveiled a previously underestimated benefit of rich-soil farming: 
that it sequesters atmospheric carbon dioxide at an incredible rate.

Micro-organisms and organic matter in healthy soils ‘store’ carbon, and 
initial research suggests that farmland may have the potential to sequester 
as much CO2 per hectare as a forest. But not all farmland is healthy: much of 
it over the years has been denatured by industrialised agricultural 
practices. Plants form a ‘carbon highway’ from atmosphere to soil, and this 
process of turning air into soil has four stages: the first is 
photosynthesis, whereby plant leaves use the sun’s energy to absorb carbon 
dioxide and separate the carbon and oxygen to form sugars; secondly, 
resynthesis occurs inside the plant, where the sugars are transformed into 
more stable carbon compounds; thirdly, exudation and the release of organic 
matter happen when plants exude carbon into the soil through their roots, and 
when leaf, stem and root matter enters the soil through the natural lifecycle 
process; and fourthly, humification takes place when soil microbes decompose 
plant carbon into a more stable form (humus).

All farmland employs the first three stages, but much intensive agriculture 
fails to maintain the fourth stage, the soil microbial life. It is the 
microbes that make the humus, storing carbon in the soil and preventing it 
from re-oxidising to the atmosphere. Humus also provides nutrition to plants 
and, like a sponge, holds on to the water content of the soil.

Rich-soil farming increases soil organic matter and microbial life by 
maintaining a balance between the organic matter removed from the land as 
crops and that returned to the land as compost or manure. Nitrogen-fixing 
crops are used to fertilise the land and support soil life, and their high 
growth rates rapidly sequester carbon. Natural pest controls avoid poisoning 
microbes and promote insect and animal diversity, in turn sequestering more 
carbon dioxide because the very bodies of Earth’s life forms are made of 
carbon. Maintaining soil cover and adopting minimal tillage avoids the 
oxidisation of carbon from the soil and keeps microbes alive with a constant 
supply of food from plant roots.

The prototype growers’ carbon calculator showed that even on a small scale a 
farm employing rich-soil practices can sequester so much carbon that even if 
the farmer uses diesel tractors and four-wheel drive vehicles and engages in 
other fuel-intensive activities, soil sequestration will still make it a net 
carbon sink.

Further calculations suggest that on a global scale, rich-soil farming could 
have a sequestration potential so powerful that it could turn back the carbon 
clock. These figures are backed up by the latest science. A 2007 study for 
the Intergovernmental Panel on Climate Change estimates that if world 
agriculture adopted best practices to increase soil organic matter content, 
it could mitigate 6 to 10 billion tonnes of carbon dioxide equivalent per 
year by 2030, which is between 20% and 35% of current annual global emissions 
(29 billion tonnes per year). As the world has approximately 5 billion 
hectares of agricultural land, this equates to a sequestration rate of 
between one and two tonnes of carbon dioxide per hectare, which, considering 
the growth rates of many plants, could be conservative. For example, recent 
research has found that forests can absorb over 8 tonnes of carbon dioxide 
per hectare every year for hundreds of years, and if very best practices were 
adopted, rich-soil farming could potentially match this. To quantify the 
sequestration potential of best farm practices, CFF is building a database of 
soil samples and changes in organic matter content from year to year.

To mitigate 100% of current global emissions, the world’s agricultural land 
would need to sequester an average of 6 tonnes of CO2 per hectare per year, 
and research so far shows that some systems can achieve this. Anything above 
that level would begin to turn back the carbon clock, bringing down 
atmospheric carbon dioxide levels to that of consecutive previous years. CFF 
believes that rich-soil farming can produce quality food for a growing world 
population whilst enhancing biodiversity, food security and healthy 
ecosystems, and at the same time mitigate significant amounts of global 
carbon dioxide.

At the time of writing (August 2009), the prototype growers’ carbon 
calculator is being field-tested and further research is being conducted. The 
calculator will undoubtedly need to be further calibrated and fine-tuned. But 
what is not in doubt is that rich-soil farming – indeed, gardening too – has 
an enormous and growing part to play in addressing climate change.

Climate Friendly Food launches the carbon calculator for organic growers in 
October 2009 (non-organic version launching 2010), together with the world’s 
first low-carbon food certification programme. For more information visit 
www.climatefriendlyfood.org.uk With thanks to Jonathan Smith for his 
important contribution to this article.

Mukti Mitchell is a carpenter, sailor and author and a pioneer of low-carbon 
lifestyles. www.lowcarbonlifestyle.org