Creating a healthy soil at Highbridge Community Farm

Climate change and the ethos of HCF

Most of us are familiar with the broad issues of climate change; an increase in atmospheric carbon dioxide (CO₂) concentration from 278 ppm in the preindustrial period (circa 1750) to 405.5 ppm in 2017; an increase of the greenhouse gas methane from 722 ppb to 1859 ppb in the same period, an increase in nitrous oxide from 270 ppb to 330 ppb in the same period. (Lal, 2019) This has already raised global temperatures by over 1⁰C since the Industrial Revolution with dire consequences as exemplified by the increase in frequency of extreme events throughout the world. Furthermore there is the real likelihood that we will miss the target set at the Paris Climate Conference (COP 21) in 2015 of limiting global warming to 1.5⁰C. (IPCC (Intergovernmental Panel on Climate Change, 2018)

The Highbridge Community Farm ethos (HCF) statement says "We have evolved from the Transition Movement and retain their founding principles - a community-led response to the pressures of fossil fuel depletion and climate change, supporting local economies and moving towards a more viable and sustainable future.  Now a mutual benefit co-operative society in our own right, we work together to produce food for ourselves with minimum use of fossil fuels and chemicals.  We support growing techniques that maintain the natural balance of the soil, preserve wildlife and their habitats, and encourage biodiversity.

Over the nine years of our existence our aim has been to grow good organic food. We have managed the soil to obtain good crops, without ever really addressing the issue of how to  improve the health, fertility and productivity of our soil in an environmentally sustainable way.  Ideally this soil should be resilient to be able to cope with whatever crop is planted in it and cope with whatever combination of weather events that is thrown at it. Probably the best measure of soil health and resilience is one with a high organic carbon content. This is in line with the Climate Accord proposed in Paris in 2015 which initiated the 4 per 1000 programme of raising Soil organic carbon (SOC) in world soils at the annual rate of 0.4% per year to a depth of 40 cm. (Chambers, 2016)  The UK signed up to this initiative and Environment Secretary Michael Gove has undertaken to deliver on this ambitious goal by supporting soil health improvements in the UK. (Eldridge, 2018)

There is an added benefit of raising SOC; the potential lowering of atmospheric CO₂ on a worldwide basis by raising SOC is approximately 84 ppm of CO₂. This burying of SOC in the soil in the form of humus is called sequestration. So raising SOC at HIghbridge Farm will be a win:win. We can play our part at HCF to produce a better, more resilient and productive soil and our efforts will benefit everyone if global CO₂ levels fall!

What is a healthy soil?

Dr F Crotty states "Soil health can be defined as a soil's ability to function and sustain plants, animals and humans as part of the ecosystem." She identifies five main factors that impact the health of the soil and can have a large influence over its capability and resilience to function; they are:

1. Soil structure
2. Soil chemistry
3. Organic matter content
4. Soil biology
5. Water infiltration, retention and movement through the profile (Crotty, 27 July 2017).

Farmers tell us that a good soil

·         drains well and warms up quickly in the spring

·         does not crust after planting

·         soaks up heavy rains with little runoff

·         stores moisture for drought periods

·         has few clods and no hardpan

·         resists erosion and nutrient loss

·         supports high populations of soil organisms

·         has that rich, earthy smell

·         produces healthy, high quality crops and grass

·         are easy to work in a range of conditions.                                                                                                 (LEAF -LInking Environment and farming, 2016)