My most vivid childhood memories all concern soil. I remember spending a lot of time sitting in the garden building mud pies, naming my pet woodlice and throwing worms at my sister. Now, I spend most of my time thinking about the very thing I once played with. It is wonderful stuff.
If you look at soil under a microscope, you see an intricate honeycomb structure of soil pores filled with microorganisms, air and water droplets. Soil is the beehive of the undergrowth that filters our drinking water and recycles nutrients, and creates the rich fertility that feeds us. Microorganisms, along with nematodes, fungi and all sorts of bizarre looking creatures, give structure to the soil by producing glues, much like a honeybee does with nectar. Without them soil is essentially useless.
Upsetting the balance
Soil is Mother Earth’s gut – its microorganisms digest her food while her flora produce the necessary bacteria and yeasts to keep her healthy. But much like our own gut, our inability to see these flora and fauna with the naked eye leaves us disconnected from their fundamental importance. We feed our guts – and that of the plant world – with toxins and foodstuffs we know we shouldn’t, and in doing so reduce the good bacteria and increase our chances of disease.
Circle of life
Soils anchor root systems, allowing plants to grow, vines to climb and trees to spread their canopies far and wide. When branches fall, soil-dwelling creatures such as woodlice, centipedes and spiders start the process of decay by feeding on the wood. Soil micoorganisms and fungi then get to work on breaking down the cellulose and lignin in the wood until eventually there is nothing left but nature’s own mulch. Without the functional role of soil microorganisms and fungi in this process, many of Britain’s invertebrates would not be able to survive. The interaction of soil biota is profoundly important to the health of soil, but as George Monbiot and others have said, ‘We are treating our soil like dirt.’
Trophic cascades
Monbiot is trying to ‘rewild’ Britain to enhance biodiversity, but his focus lies mainly on matters above ground. We also need to recognise and champion the life below it. Take the notion of a ‘trophic cascade’, a process that releases lower trophic levels from top-down control by predators. For the soil, the top ‘predator’ is the nematode, a predominantly microscopic worm-like animal.
Nematodes can play a parasitic role and attack plants, but many feed on fungi, bacteria, protozoa and even other soil nematodes and, as a result, keep their numbers in check. They also indirectly affect plant fitness. Insect-parasitic nematodes, for instance, are natural enemies to predators such as the ghost moth caterpillar, whose larva feeds on the roots of a variety of wild and cultivated plants. In one study that looked at this interaction specifically on bush lupine, it was found that in a healthy system insect-parasitic nematodes not only kill the caterpillar but also increase the survival and production of this flowering shrub species. If soil biodiversity is not respected this type of synergistic ‘biological control’, which the authors believe is not uncommon elsewhere, is lost and with it the ability to regulate the population of other organisms. In other words, a trophic cascade ensues.
If soils are healthy, nematodes also convert nutrients into forms that are available to plants, so they are fundamentally important to food production systems. However, because we underestimated the importance of having an intact and diverse soil system, nematodes have been subject to physical disturbances or chemical inputs that reduce favourable species and increase plant-parasitic nematodes (the ones that farmers don’t want). In some intensive farming systems these have now become major pests and farmers are using yet more dangerous chemicals in an attempt to control them.
Reducing complexity
Meanwhile, earthworms – the architects of the soil that can be seen with the naked eye – have long been treated as pests by grounds people and gardeners who try to maintain the aesthetic value of their lawns. Up until 2003, when it was found to be carcinogenic, the toxic chemical chlordane, a persistent organochlorine, was used to kill worms in gardens, lawns and even on fields of corn and citrus. While it has been outlawed, alternatives still remain that deplete the soil of worms and microorganisms.
What we failed to recognise is that worm casts (the squiggly piles of soil you see sometimes) are in fact richer in plant nutrients than soil, with about three times more calcium and several times more nitrogen, phosphorus and potassium. While they are not aesthetically pleasing, they provide the natural fertiliser needed to replenish the soils. It is a complex world down there, but our lack of understanding has meant that we have been slowly reducing the numbers of certain species and the nutrient regulating capacity of the soil food web.
Working with nature
Seven million front lawns are now paved in Britain, and many back gardens are turfed and mowed on a regular basis. Turf grass requires more water and maintenance, has minimum wildlife value and low aesthetic value compared with a diverse garden. Despite this, turf sales, including sales of fake grass, continue to increase as our busy lives prevent those of us with gardens from tending them.
To ensure wildlife thrives we must take a holistic perspective that includes above- and below-ground diversity. As soil microbiologist Elaine Ingram has said, agriculture should be the art of nurturing soil life.
Agricultural land that is less disrupted such as pastures, hay fields and orchards tend to host more beneficial nematodes, while the application of organic residues help to suppress plant-parasitic nematodes. And for soils that are depleted in certain nutrients, adding microbial ‘wildlife’ back to the soil through a good compost mix will, over time, lead to improving yields. Further, reintroducing earthworms for instance, can initially increase pasture growth by as much as 70–80%, and in the long term this works out at about a 25% gain in growth.
For gardeners, disruption could be all but eliminated through no-dig techniques (also known as ‘no-till’ for you farmers out there). Green mulch and green manures – such as mustard, rye and vetches – replenish the soil with nutrients and keep it covered from the elements, while raised beds eliminate compaction from trampling. But each crop has different requirements so it is worth doing some research before applying these methods.
To rewild poor soils, wormeries, wildflowers and native plants all provide simple solutions. Native plants can be more beneficial to soil health and wildlife than non-native species, as they are suited to local soils and climate. Comfrey, for example, is a member of the borage family native to much of Europe, including Britain, with an expansive root system that can cycle nutrients and accumulate excess nitrogen in its leaves. The leaves can be picked and steeped to create a liquid fertiliser that, in turn, increases microbial decomposition in the soil. Not only is comfrey edible, it makes fantastic mulch, attracts beneficial insects and has medicinal properties – it is a good all rounder.
Telling tales
Monbiot believes that in order to succeed at rewilding Britain we need to fill our ecosystems with wonder and enchantment. While there are storytellers for the countryside, there are fewer for the soil, but this is starting to change.
To mark the UN International Year of Soils, the Centre for Contemporary Art and the Natural World have created a Soil Culture programme that brings soil to life. Together with the Soil Sisters, it is using art, storytelling, cultural exchange and food to highlight the threats and solutions facing Bristol, Britain and the rest of the world. Soil has an unconventional beauty and contains so many memories that our children may never be able to share if it is paved over or depleted of life.
I haven’t lost my love for soil, but the passion has been harder to maintain as I moved from village to city. I am sure the same can be said for a lot of us. We just aren’t allowing ourselves the time to reconnect with soil, feel it in our hands and give thanks to the microscopic world for the marvellous job it does of feeding us – when it is healthy and happy. We need to care for it, so it can care for us.
Photograph: CIAT
