Understanding the Living Soil: There Really Is a Universe Beneath Our Feet  

The mineral soil, the silt, sand, and clay, even the roots, are home to all kinds of macro- and microorganisms (also known as the soil biome) that spend their time eating plant residues and each other, and in the process transform and store nutrients, and build soil structure. Just one teaspoon of healthy soil can contain more microorganisms than the total number of people on Earth. That’s amazing, right?  

In fact, soil is a complex and living system that we hardly understand. Soil scientists call the earthy world of microorganisms the ‘black box’. We’re still gaining knowledge of these microbes and how they interact with each other, their environment and plants. DNA sequencing and other amazing scientific advances have transformed our capacity to understand more about this underground world, and faster than ever before.  

Why it’s important to act on soil health now 

Earthworms are typically present in healthy soils. Darwin wrote the page-turner The Formation of Vegetable Mould through the Action of Worms, with Observations of their Habits back in the 1800s. It was a bestseller. He tells us that earthworms can break down at least their weight’s worth of plant materials in a week, grinding them into a powder-like [compost], known as castings, that helps nourish the soil. Raising worms and farming their castings is a super low-tech system that produces stable organic fertiliser. This approach can easily be used on a small farm or even in an apartment. Worms don’t take up much space.

Arbuscular mycorrhizal fungi (AMF) form mutually beneficial relationships with plants. They have an extensive system of branches called hyphae that insert themselves into the actual root cells, extending the plant’s access to water and nutrients, especially phosphorus, far beyond the roots’ reach. In return, the fungus gets sugars from the plant. AMF also produce glomalin, a kind of glue that holds soil particles together and provides an ideal habitat. One scientist in British Columbia has written a book on how trees communicate and share nutrients through their roots and the fungal network that connects them. It’s amazing how different species cooperate.

Mycobacterium vaccae, a bacteria found in soils, has been shown to work as an antidepressant. They produce a fat that seems to counter stress-related inflammation in our bodies that can lead to depression. The connection isn’t completely understood yet, but this little bacterium may well have the ability to counteract our natural stress responses. Maybe that explains why I am happier with a little soil under my fingernails. 

Dung Beetles are another helpful sign of healthy soils. They live in many different ecosystems on every continent, except Antarctica. The beetles feed on manure and, depending on the species, may transport it to their underground tunnel or roll it into a ball and bury it in the soil to lay eggs. And here’s a fun fact – they also orient themselves using the sun, moon and Milky Way as a guide. 

And finally, soil enemies… There are plenty of pests and pathogens in the soil too, and these can pose a risk to healthy crops and people. An unbalanced ecosystem can result in the loss of predators of these pests. For example, nematodes (microscopic roundworms) can be pests, but predatory nematodes such as the Steinernema species can attack grubs in the soil, including common cotton pests like pink bollworm and armyworm. A well balanced soil biome helps maintain these beneficial species of nematodes and prevent outbreaks of cotton pests.