“Earth Stood Hard as Iron”: the importance of soil

“In the Bleak Midwinter”* there is still plenty of life in the earth beneath our feet, though during the colder months underground activity slows down beneath the frosty crust. Our soil is a finite resource, and if we know something about how it came into being over millennia, we begin to realise how precious it is, for it takes up to 400 years to form one centimetre of topsoil, that layer of fertility which supports growth. Undergoing weathering (alternating cycles of rain, ice, heat), the different types of rocky surfaces of Earth gradually cracked and eroded so that lichens and mosses were able to establish, drawing important minerals from below. As these early lifeforms decomposed they provided enough nutrients for other plant life to root and grow. This process repeated until the resultant soil (with its varying amounts of sand, silt, clay and organic matter), was deep enough to support vegetation, from fungi to forests, that covered Earth’s surface wherever climate and conditions were hospitable. 

 A vast number of lifeforms have also evolved within the soil, which is home to a quarter of all Earth’s species, from foxes and rabbits down to nematodes and protozoa.  ‘Detritivores’ live in the leaf litter on the surface; creatures such as slugs (with their 27,000 teeth!) and woodlice, along with fungi and bacteria, begin the task of breaking down the leaves which are then incorporated into the soil.

Worms are at the top of the vast and intricate soil-web; they pull down plant detritus, eat soil, and excrete the resultant ‘vermicompost.’ Through their activity they mix up all the particles and form channels in the earth, enabling oxygen and rain to penetrate. In bitter winters earthworms burrow deeper into the ground and become dormant, wrapping themselves into tightly tangled balls and exuding an insulating slime which is high in nitrogen, helping to bind soil particles together.

With high worm activity the soil becomes a water holding ‘sponge’ that drains well, creating the best medium for plants to thrive. Good water storing capacity of our soils is vital, as the ‘sponge’ provides resilience against drought and flooding  and also enables the soil to store vast amounts of carbon. The excretions of earthworms make nutrients available for the rest of the unimaginable number of underground life forms – it is said that just a spoonful of good soil can hold six billion micro-organisms!

Scientists have long known that certain fungi have a symbiotic relationship with plant roots. These fungi send out gossamer-fine tubes (hyphae) which mingle with the roots, combining to form a ‘mycorrhiza’ ( Greek: literally fungus-root). The mycorrhizae together form a widely spreading network in the soil. From plant roots the fungi siphon off food - carbon rich sugar produced during photosynthesis. The plants, in turn, obtain nutrients that the fungi have acquired from the soil by means of enzymes that the trees don’t possess. More recent research has found that this amazing network, known colloquially as the ‘Wood Wide Web’, has other functions, which allow the plants themselves to interact and send messages underground to one another, to cooperate, and sometimes to compete. For example, a tree under attack from, say, insect infestation, can ‘tell’ another so that it can raise a defensive response in good time. It seems that, rather than simply being independent individuals, the trees are part of a social network extending far and wide, linked by the equivalent of the fibre optic cables of our own World Wide Web. But they definitely got there first, by millennia!

 Nutrient exchanges and communication between a mycorrhizal fungus and plants. 

By Charlotte Roy, Salsero35, Nefronus - Adapted from https://commons.wikimedia.org/wiki/File:R%C3%A9seau_mycorhizien.svg, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=92921450

You’ll already be aware that soils worldwide are being degraded by industrial scale farming as well as being concreted over for building. The UN has warned that there are only 60 harvests left in the world’s denatured soils, which will lead to food shortages. Badly managed soils lead to erosion (America’s ‘dustbowls’ being an extreme example), susceptibility to flooding, and massive carbon loss to the atmosphere. To help on an individual and community level we can learn about No-Dig Gardening, Permaculture, Regenerative Farming or Sustainable Agriculture. Each of these practices preserves soil structure: digging and tilling are minimised, organic matter is added to the soil surface leaving nature to do what it does best, and a variety of cover crops are used so that the earth is never left bare. This results in soil that is teeming with life, where plants are able to root deeply and natural emissions of greenhouse gases are reduced. The need for artificial fertilisers (with their high carbon footprint) and reliance on pesticides is minimised. The Government’s Environmental Land Management Schemes (ELMS) will encourage these initiatives - IF properly funded.

In our gardens we can mimic nature, leaving plants in situ to cover border soil over winter, providing habitat for myriad creatures; if we wish to cut back in spring, stems can be left in a pile until May, so that hibernating insects can escape before the material is added to the compost heap and eventually returned to the soil. Green manures can be used as cover crops in the vegetable garden.

 Autumn leaves on the grass can be raked up if they’re lying thickly, and either spread on sheltered beds or used to make wonderful leaf mould. We can aim to be pesticide free. Additionally, we can minimise expensive hard landscaping and where possible use materials that are permeable. And of course we must shun peat based composts. Peat bogs hold 30% of Earth’s organic soil carbon, and must be preserved.

I hope this introduction to a very complex subject will give you some insight into why “EARTH MATTERS” and encourage you to be aware of, and support initiatives to restore our soils - for the sake of biodiversity, to contribute to climate stability, and to sustain healthy food supplies for the generations to come.

November 2021

Sources:

*Christina Rossetti

 Wood Wide Web information: https://youtube.com/watch?v=yWOqeyPIVRo&feature=share

Wohlleben Peter "The Hidden Life of Trees", 2018,