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The secret to perfectly balanced and fertile soil, even in winter

A winter veg garden is still alive under the frosty surface - Gap Gardens 
A winter veg garden is still alive under the frosty surface - Gap Gardens

In these shortest of days, life below ground is quiet but active, many invertebrates are surviving, like travellers to Mars, only as eggs or chrysalises.

Sean Borodale, the poet, puts it better: “the sleeping time, the closed membrane of the egg – half of eternity’s symbiosis. This is how winter stores its greater proportion, in preoccupation: packets of forming anatomy.”

Leatherjackets, the pupae and larvae of all sorts of insects, as well as frogs and snakes, wait out the winter down below the frost layer where conditions remain constant and steady. If the top layer of soil dips below seven degrees C, biological activity slows down considerably.

Worms burrow as far as 6ft down; some produce an antifreeze called glycol; some wrap themselves in mucus slime. Mycorrhizal fungi survive winter as spores.

Archaea, soil microbes only recently discovered, are thought to be among the most ancient living things on or in the earth. They are unperturbed by extremes of circumstance, living in hot springs as well as permafrost. Strange and opaque are the ways of the underworld.

Soil is a mixture of organic matter, minerals, gases, liquids, and organisms. It is teaming with organisms, more than a billion to the gram – an astonishing thought. Most of them, 98 per cent, humans have not identified.

Disrupt this equilibrium at your peril – I am only beginning to understand it is best to disturb your soil as little as possible. The expertly dug and raked plot can be a thing of beauty, but I have always been too busy, too much a “short cuts” merchant, to care for the tidy winter garden.

It has its satisfactions, but I realise now that my recalcitrance may have made me, however inadvertently, better in tune with the soil and the commonsense way of gardening.

Why? Because the “pedosphere”, as the scientific classification of the soil layer of the planet is called (companion to the more familiar “atmosphere”), is the medium for plant growth; water storage; the atmospheric modulator extraordinaire; the great carbon sink. It acts as a global engineering medium and recycling facility, abounding with animate life.

A natural soil profile shows how shallow the fertile zone can be - Alamy
A natural soil profile shows how shallow the fertile zone can be - Alamy

The whole soil-plant organism reminds me of a big digestive system in reverse, consuming apparently waste products and creating delicious food at the end. Contra David Attenborough it is the soil, not the ocean, which contains the most abundant biodiversity on earth, and is the least understood.

Billions of organisms, and 11 million species. It’s almost a spiritual experience, running soil through your hands, kneading the clod to feel its make-up and propensities, how it sticks together or to your fingers, smeary or granular, scrunching into a stable ball or crumbling away.

When in a new garden it is never long before, like Mole in The Wind in the Willows, Mr B [aka Julian Bannerman], plugs in his paws, catching the telegraphic signals from down below. He looks for molehills, those despised and anxious-making heaps of delicious friable loam on your lawn.

Moles are the megafauna of the underworld, mining their underground corridors for worms – and worms are much more abundant in a healthy open loam. Respect the mole and live with his hills, for he represents the good health of your underworld.

We know that moles are blind – did we also know that, although their ears are tiny, they are highly tuned to vibration? But the amazing mole nose and sense of smell is the key. The mole sniffs out a worm in the dark, and calculates the direction stereoscopically, a navigational method increasingly recognised as important for salmon and shearwater migration in sea and air.

But, although mole’s nostrils are only millimetres apart, they give accurate separate directional readings to the brain. So, if the left side is blocked, poor moley goes round and round to the right, and vice versa. Block both nostrils and, flummoxed, they miss the worm completely.

I remember now with shame how, in the 1980s, we would buy bales of sphagnum moss peat to sweeten and lighten our garden soil. Now, biochar is the trending thing, a fantastically stable charcoal form of humus (my sons mock me for pronouncing it like the Mediterranean chickpea dip) whose soil benefits have been understood since ancient times. Most normal garden soils need to be opened and lightened up, and we all know that organic matter is the magic soil improver.

Another confession: until recently, I thought compost was for pedants. Compost convert that I am, I intend to join the compost makers in a big way in our new garden. The bounty of veg we grew this first year here on a patch left untilled for 30 years was miraculously without pests and diseases. No blackfly on the beans.

Garden designer Isabel Bannerman has come to appreciate no-dig methods and home made compost -  Jay Williams
Garden designer Isabel Bannerman has come to appreciate no-dig methods and home made compost - Jay Williams

This is how we need to keep it. Our experience this first season seems to confirm that garden tools break up existing structure in undisturbed soil, the structure that maintains and develops a honeycomb of small air passages.

Many or most of these have been made by either worm movement (fantastically slow, which is why they get massacred by machine tools) or generations of hyphae – tiny threads put out by mycorrhizal fungi, which push microscopic boreholes through the soil and then die, leaving only air or water.

While alive, they symbiotically provide the biological link between root and soil, taking sugars down from plants and water and mineral nutrients such as phosphates up to the plants.

What else can we do for the soil? We can leave the leaves, or at least collect them in a pit in the garden where they will make crumbly brown mulch with immodest haste. Three times this November, perfectly sane people have told me how dispiriting it is to rake up leaves from their lawns each day only to have more fall in the night – somehow implying the spitefulness of trees.

“Why bother though?” I beg of them. “What does it matter if your lawn looks a bit of a mess?” Why not watch the miracle take place instead? Have you ever seen how leaves stick up in the morning like the shark’s fin in Jaws, pulled down into the subterranean nightclub by so many wriggly hermaphrodites? They are feeding the soil, aerating the lawn without you having to lift a finger or a rake, let alone a leaf blower.

Leaving vegetation also reduces soil erosion and the curious compacting effect of heavy rain on bare soil. It stops “crusting” in dry periods. A good, deep mulch will insulate your soil, protect roots and reduce the frost layer. This will protect the roots of perennials and tender things like dahlias, too. Leave as many plants to die and feed that earth as you dare. Generally we have approached the whole business of growing stuff the wrong way, from the leaf down instead of the roots up.

Isabella Tree, rewilder-in-chief, has said in an interview that: “If we only focused on the soil, we’d realise it’s a living, complex organism … everything comes full circle back to the soil in the end, but we are only beginning to start thinking about it properly. Before the war, as a farmer you would smell, taste, and touch your soil – but now tractors have air-conditioned, sealed cabins, so we’ve lost touch with it.

Soil has so much to teach us, yet we know so little about it. We need to connect humus with humility and start to respect it again. The good news is how quickly soil seems to restore itself, given the opportunity.”

In the darkness of the under-land, there is so much for us to learn and understand. And winter is a good time to think about and look after our garden soil, the earth. I recoil rather at the use of the term “dirt”, it seems so dismissive, redolent of an attitude problem with things that are mucky. But “earthiness” and, these days especially, being “down to earth”, is a valued quality. I never really considered why the ruling body of the organic movement is the Soil Association.

Soil is the point; the key thing is the earth beneath our feet. Soil needs to be understood better by gardeners, it needs to be cherished as an organism of great complexity – not just dirt. Perhaps it is helpful to think of it more like Philip Pullman’s “Dust”, the all-empowering linchpin of life on earth.