The question ‘What have soils ever done for us?’ brings lots of replies: the provision of food, fibre and fuel, a source for pharmaceuticals, water purification, flood and climate regulation to name but a few. Although we understand the need for fertility, light, water, etc, we tend to regard soil as just the medium we pop our plants into, rather than a treasure trove. However, scientific research in recent years has revealed how rich, complex and full of life it really is.
“Soil is an incredible, vital, and undervalued resource. It takes up to 400 years to make one centimetre’s depth of soil. One teaspoon of soil contains more living things than people on Earth.” Royal Society.
Sadly, the research also reveals that soils have been in decline for a very long time, in reality since humans took up the plough. Moreover, soil loss rates have speeded up dramatically since the adoption of much more intensive farming methods and governments are now concerned to address the problem with regenerative farming approaches...
A key part of these approaches is sustaining the biodiversity needed to maintain a healthy soil but there are lots of other things that farmers and gardeners can do to maintain their soils and keep them healthy.
Healthy Soils, Healthy Veg The four main components of a healthy soil are mineral particles, water, air and organic matter. This last is decayed material that was once alive; it gives soil its natural fertility and also binds the mineral particles together into a structure that allows air and water to pass through.
The organic matter includes a huge diversity of soil organisms, from microbes up to earthworms and beyond. These maintain the natural cycles of decay and regrowth that provide nutrients for plants to feed on. In fact, an easy way to assess the health of your soil is to check how many earthworms you have.
Key tips for soil health
- Top dress with lots of compost or mulches to maintain organic matter levels. These surface layers protect the soil, keeping it warm in winter and letting water penetrate in summer. They decay slowly to improve the soil. Lots of organic matter helps it to hold more water and prevent flooding and nutrient loss via leaching. It also makes soils resilient to drought.
- If soils are left bare, heavily dug or rotavated, they’re unprotected and also release carbon into the atmosphere, so consider low-dig methods, along with growing cover crops or green manures.
- Respect soil life. Most organisms are beneficial and contribute to soil health.
- Nature provides plenty of nutrients. If they’re topped up with composts and animal manures, man-made fertilisers need only be used sparingly, if at all. Excess amounts can lead to water pollution and disruption of the natural nutrient cycles.
- Consider adding biochar and encouraging mycorrhizal fungi. Biochar is charcoal that absorbs dissolved soil nutrients and releases them slowly, as well as being a long-term carbon store itself. Mycorrhizal fungi interact with plant roots to exchange sugars and soil nutrients, benefitting both, but they don’t survive if the soil is repeatedly disturbed. The RHS website is an excellent source of information on both of these.
Resources
www.nsalg.org.uk/growing-advice/gardening-methods
Editor's Note: This article was commissioned from Alison McCrea, MCA's resident soil scientist, by Leek Town Council to circulate to the town's allotment holders.