WORLD AT OUR FEET
In our pursuit of the perfect garden, we often overlook the very thing it relies on. So how can we improve the health of our soil – and our plants?
As gardeners we generally regard our glorious plants and well-tended designs with the utmost pride, but below ground there is a whole other world in our care, a very secret and mysterious one. Perhaps more like a universe, it is this which feeds our gardens, sustains our wildlife and gives us life on this planet, yet we overlook its staggering complexity and importance in our everyday lives. This is the universe of the soil, and more importantly the life within it.
Our soil is under threat on a global scale. Our planet has already lost 70 per cent of its fertile topsoil, mainly through industrial agriculture increasing the rate of erosion. A United Nations report states that globally we are losing 24 billion tonnes of topsoil every year – that’s the area of 30 football pitches every minute. A recent government report claims that the UK loses around 2.2 million tonnes of topsoil every year. With this current trajectory we could lose most of our fertile soil in the next 60 years, and it is worryingly most of this damage has only been done in the past 150 years. Among all the doom and gloom, you may be wondering how this relates to you as a gardener.
The RHS estimates there are 24 million gardens in the UK and that is an incredible amount of land when added together. It is
easy to separate our gardens from the wider environment, to hear the plea of the natural world but sometimes still to act against our better instincts in pursuit of perfection in our own space. But it is in our management of the soil that we can make the most change. By altering our methods and priorities, we can make our gardens healthier for all and change the perceptions of what a good garden should look like. And perhaps the first step to take is to change our idea of what makes a ‘perfect’ garden.
This is a notion being tested in the USA with many institutions and gardens shifting their idea of what constitutes a ‘perfect’ lawn. Last year I visited Chicago Botanic Garden, New York Botanical Garden, Brooklyn Botanic Garden, Harvard University, Mount Cuba Center in Delaware and Chanticleer in Pennsylvania; not only do all these gardens accept the odd clover in their lawns, but they use its beneficial qualities – retaining nitrogen while providing fodder for emerging queen bumblebees.
In the USA, as in Britain, there is currently a sustainability renaissance. The destruction of soil caused by industrial agriculture has led to great work being carried out in regenerative farming. Both horticulture and agriculture have a lot to teach each other on the topic of sustainability. Research on the regeneration of soil has found its way
into American horticulture, helping to develop new practices with some amazing results.
Rather than assessing the health of the soil purely in terms of its chemistry – that is, nitrogen, phosphorus and potassium (NPK) – management methods now focus more heavily on the biology of the soil, the microbes, bacteria, protozoa, fungi and other microorganisms. A single teaspoon of rich garden soil can contain up to one billion bacteria and several metres of fungal filaments along with several thousand protozoa and nematodes. A pint of soil can contain as many organisms as all the humans who have ever lived. Each plays a role, with nutrient-rich bacteria being consumed by larger predators (protozoa and nematodes), which in turn release nutrients back into the soil for use by plants.
The use of mycorrhizal fungi in gardening has seen a huge increase, and for good reason. When partnered with a plant, the fungi can increase water uptake by 40 per cent (increasingly relevant as our climate changes) and strengthen the plant to fend off attacks from pathogens. Encouraging the native mycorrhizal fungi in your own garden is likely to give far better results than using the commercial product, as ‘native’ fungi have higher survival rates when released back into the garden from which they came. In fact, certain places now follow a form of cultivation called Natural Korean Farming (NKF), which is based on the idea, first developed in Korea, of growing and using your own native microbes, especially fungi.
The Chicago Botanic Garden has an entire department dedicated to microbial life in the soil. There is a test plot that tracks the effectiveness of mulches, bio-char and compost extractions in gardens. Compost extractions work by removing a sample of microbial life from compost through an aerobic water system, a process known as ‘brewing’. This increases the microbial populations then applied to the soil. The results are directly linked to practical work in the gardens.
Organic fertilisers and liquid feeds such as seaweed provide a good alternative to synthetic fertilisers such as phosphorus. The mining of phosphate rock itself is unsustainable. Soil is damaged during extraction, erosion and compaction result and greenhouse gases are released. Much of the phosphate leaches into water sources, poisoning them and the surrounding soil. In any case, phosphate reserves are predicted to run out by 2030.
It is now more urgent than ever that we use sustainable practices in our gardens. The one thing we do know is that there is no silver bullet or single answer to any of this. To make our gardens truly sustainable, we must start to question our gardening practices and learn from current research. The universe beneath our feet is very much hidden from us, but if we want our gardens to remain for future generations, we need to start looking deeper.
USEFUL INFORMATION Four good books on the subject are The One-Straw Revolution by Masanobu Fukuoka (NYRB Classics, 2009), The Soil Will Save Us by Kristin Ohlson (Rodale, 2014), Practical Organic Gardening by Mark Highland (Quarto, 2017) and The Biochar Debate by James Bruges (Green Books, 2009).
NEXT MONTH Joshua offers a practical guide to getting the best from your garden soil.