One of the most inspiring clips I have watched recently is ‘Why soil is one of the most amazing things on Earth’ by BBC Ideas (link below). It talks about how this essential resource is being degraded, describes the role it has in the nitrogen carbon cycle of the earth and abundance of biodiversity it hosts. All good news for the planet – and our gardens! I dug a bit deeper to find out more about the treasure beneath our feet.

Soil-1

What is soil?

If I asked my children what soil is, they are likely to refer to the fun muddy stuff that makes up most of our back garden at this time of year! But what is it made of? The Rainforest Alliance describes soil as a “…natural body made up of minerals, air, water, organic matter, and living organisms.” Living organisms like earth worms break down and mix up our soil, creating deep gaps for air and water to pass through as they go. The Rainforest Alliance goes on to describe soil as a non-renewable resource, created over tens of thousands of years through the weathering of bedrock. They talk about how the soil organisms like fungi, interact with roots in hidden networks that transfer water and nutrients between plants – but the best bit of the research uncovered that chemicals allowing plants to communicate with one another are also transferred!

Soil-2

Function of soil

We perhaps take for granted that soil is abundant and productive in the UK. But the Government, through the Environment Agency, produced a report in 2019 that summarises risks to the health of our soil. The opening paragraph explains the crucial functions of soil in holding 3 times as much carbon as the atmosphere, reducing the risk of flooding by absorbing water, providing habitats for wildlife, and delivering 95% of food supplies. So, we are talking about a resource that is critical to maintain life on earth.  

Types of soil

When thinking about what plants to choose for our gardens, knowing what type of soil we are working with is essential. The Royal Horticultural Society explains in detail the characteristics of 6 types of soil found in the UK: Clay, sandy, chalky, loam, silt, and Peat. The main factor defining each one’s gardening characteristics being particle size.

Clay soils have the smallest particles, less than 0.002mm. They are heavy, can get compacted easily and are high in nutrients. They can be very wet and cold in the winter and get baked hard and crack in the summer. Clay soil smears easily and can be moulded and smoothed.

Silt soils are rare in gardens and have particles 0.002-0.05mm in size. They are fertile and retain moisture but are well drained, prone to washing away or wind erosion. Garden machinery and treading can easily compact silt soils.

Clematis_alba_luxurians_on_garage

Sandy soils are gritty, containing little clay, and with mostly sand particles of 0.05-2mm. They are light, dry, and warm. Often acidic, they are low in nutrients that can get washed out by rain. 

Stony soils have particles that are bigger than 2mm. Chalky soils can be stony and consist mostly of calcium carbonate or lime. They are very alkaline.

Loams are described by the Royal Horticultural society as a gardener’s best friend! They say this is because it has a perfect balance of all soil particle types. They still recommend adding organic matter regularly to loams, particularly when these soils are cultivated each year.

Plant choices for soil types

The RHS website has a comprehensive list of plants suitable for different soil types. For sandy soils it suggests lavender and buddleja. For clay soils mahonia and hydrangea, and for chalky soils clematis and dianthus. Geraniums are a plant that can thrive in all of those depending on how hardy their variety is.

Soil-4

How to protect and make the most of our soil

For those of us lucky enough to have gardens, we can play a part in protecting our soils through responsible gardening practices. The Soil Association offers tips to conserve the health of our soils. These include growing our own food and flowers, advising that leaving soil bare can mean rain can wash it and all its nutrients away. Another tip is to add organic matter such as fallen leaves, dead plants, and peat free compost to soil to help it hold on to its nutrients and to water. I sweep all my garden cuttings under my lavender bushes to let it break down and create new soil for example, or you can add a compost bin to make your own compost, though remember never to put cooked leftover food into it as it attracts rodents!

Soil-5

‘No Dig’ and ‘No Mow’ approaches to gardening also nourish the soil. No Dig involves covering areas with a material such as cardboard to exclude light and prevent weeds growing, then cover with a deep layer of organic mulch. This can be homemade compost, leaves, straw or fully rotted manure. Garden Organic are a charity that has useful information on No Dig gardening. No Mow is similar in that it aims to help strengthen the roots of plants by allowing them to grow deeper before grass or flowers are cut down.

I hope you have enjoyed a foray into the wonderful world of soil and whether you have a garden, window box or allotment, there are many ideas and options to look after and nurture this precious resource.