Today is World Soil day, but why on earth do we need a day on soils?
It’s no coincidence that our planet shares its name with the stuff. Soil, earth, or dirt, as it is known in the USA, is important. Franklin D. Roosevelt knew that – in 1936 he said ‘The history of every Nation is eventually written in the way in which it cares for its soil’ – a reflection perhaps of the fact that many great civilisations have crumbled alongside their soils, degraded through years of cultivation to the point where food production was simply not viable.
But it’s 2014, and agricultural technology is far more advanced than any of the great ancient civilisations of the past. So how are we doing? Well, sadly – we are still making mistakes.
It may be the 21st century, but we have some serious soil problems – probably the worst since humans appeared on the planet. Thirty per cent of the world’s croplands have become unproductive, with the area of soil degradation in the last 40 years amounting to an area larger than the United States and Mexico combined.
Whilst much of the worst degradation has occurred in the developing world, often resulting from the failure to maintain and build fertility, problems are seen even in the UK. Arable soils in particular have become vulnerable to droughts and floods and the future ability of these soils to maintain high yields is in doubt. One study found more nutrients in urban soils than agricultural, with the researchers suggesting that we only have 100 harvests left in the UK. Indeed, we are already seeing declines in wheat and oil seed rape yields in some parts of the UK, possibly linked to soil degradation.
Until the 20th century, when farmers’ soils grew ‘tired’ after years of cultivation, the solution was usually to move on. But as science has progressed over recent decades, soil was discovered to be a substrate holding key nutrients required by plants. As those plants are harvested, the soil nutrients are gradually depleted, and crops suffer. Recent inventions including superphosphate made from mined rock and the Haber-Bosch process (converting nitrogen from the air into a fertiliser) meant we could at least replenish the key nutrients and keep plants healthy.
But this was overly simplistic– we have wildly underestimated soil, and what it does for us. We now know that healthy soils are more than a matrix supporting a nutrient soup – they are very much alive.
A healthy soil contains millions of individuals and thousands of species: a quarter of all life on earth is in the soil. This life – from earthworms to protozoa, fungi and bacteria, as well as dung beetles and other amazing creatures like springtails and water bears – creates a complex ecosystem.
Plants have evolved to work with this soil ecosystem. Soil organisms break up and aerate soils and filter and recycle nutrients, making them available to plants through complex interactions which we are only just beginning to understand. A classic example is the threadlike fungi called Mycorrhizae – these act as extenstions to a plant’s roots and help plants choose and extract exactly what nutrients they need from the soil.
Currently, the way that most crops are farmed gives no consideration to this soil life and the relationships they have with plants. Pesticides applied to soil can damage many species.
A healthy soil ecosystem needs a good proportion of organic soil matter, which is formed largely of decomposing plant and animal matter. It’s this that gives healthy soils their moist crumbly consistency and fabulous earthy smell.
As crops are harvested, less decaying matter is returned to the soil, depleting soil organic matter, which in turn impacts the soil organisms that thrive on the stuff. Over time, this changing community of organisms destabilises the soil, causing it to dry out or become water logged more easily.
In addition, soils gradually erode, worsened by conventional farming’s tendency to leave soils bare and exposed, and damaged by compaction from heavy machinery.
In the short-term this means that farms suffer more than is necessary from extreme weather. In the long-term, it can lead to declines in yield, despite the application of chemical fertilisers. Our health may suffer too – crops harvested from conventionally managed farms have now been shown to contain less nutrients – in particular 19-69% fewer antioxidants which may be important to our health.
The founder of the Soil Association recognised this link between soil health and human health over sixty years ago and the response was to develop what was then, and still is, a radical, yet practical and workable method of farming. It’s a system that protects and nurtures the soil and the life within it by putting it at the centre of the farming system – organic farming.
I hope that World Soil Day helps create an increased understanding of why organic farming approaches are so important for the long-term sustainability of our soils, our yields, our health, and – dare I say it? – our very civilisation.
To find out more about these approaches, please download the short Soil Association briefing below.