What is Good Soil? Everything You Need to Know

Good soil is one of our planet’s unsung heroes.

It’s always hard at work, providing nutrition, water, and oxygen to plants, yet we barely notice it. We dismiss the dirt and treat the word like a slur - but healthy soil is so much more than that. It holds the key to building resilient food systems, boosting biodiversity, and combating climate change. We think the dirt beneath our feet deserves more respect than it gets!

So today, let’s focus on the fundamentals: what is soil and what makes it good? Why is healthy soil essential to growing a thriving vertical garden? Join us as we break it down for you in this blog. 

What is Soil?

Many people think of soil as a lifeless expanse of dirt, with roots acting as straws drawing out water and nutrients to form a beautiful living plant above the ground. This is far from the truth. 

Soil is a biodynamic, chemically active matrix buzzing with life. A teaspoon of topsoil holds more than 10,000 species of microorganisms and a billion microscopic cells. When combined with organic matter, minerals, water, and air, the result is a beautifully synchronised, living micro-ecology - perfectly capable of delivering everything a plant or seedling needs to survive.

Understanding Soil and Its Function

Imagine the relationship between two vital organs in your body - both deeply interconnected, passing nutrients, chemicals, and signals to each other. These interdependent organs are always working together to sustain life. The relationship between soil and plants is no different. Both are essential for each other’s survival.

Soil is a matrix of living and inert components. From a component perspective, most healthy soils are made up of a basic set of ingredients in the following approximate proportions by volume:

This basic list of ingredients makes soil sound deceptively simple. But the truth is just the opposite. When the components of this matrix are in balance, the soil is healthy. As a direct result, the plants growing within it are healthy too. But if the matrix falls out of balance and the soil becomes unhealthy, the plant suffers along with it.  

In other words, a plant is only as healthy as the soil it’s growing in.

How Soil Improves Biodiversity

Soil contributes to the local biodiversity by supporting a wide range of plant species. It’s also home to countless soil-dwelling microorganisms. In about a cup of topsoil, you’ll find at least 200 billion bacteria, 20 billion protozoa, and 100,000 metres of fungal hyphae going about their business. And let’s not forget the earthworms and other invertebrates that break down organic matter to keep soil well-aerated and nourished.

However, not all soil is created equal. To transform your garden into a biodiverse haven, you need soil with a good structure.

Good Soil Has a Good Structure

Like humans, soil must keep up with a vigorous workout routine to stay healthy. It has to make sure air flows in and out, and water flows up and down. It also has to ensure microbes get ample space and nutrients to feed themselves as well as the plant roots they're symbiotically working with. Doing all these things and doing them well is only possible with the right structure. 

A well-structured soil is porous with a soft, crumbly, sponge-like texture. It’s not dry or slimy. You can grab it, mould it, and break it apart just as easily. Healthy soil texture is a gardener’s dream as it holds moisture, drains excess water while providing excellent aeration and strong physical support for roots.

How good a soil’s structure is directly influenced by its largest component - minerals.

Let’s Talk About Minerals

When we talk about minerals in relation to soil, we aren’t talking about the type of minerals as much as their size. Soil minerals are normally classified into three groups - sand, silt, and clay.

Sand is the largest mineral type (2mm - 0.05mm), followed by silt (0.05mm - 0.002mm) and, finally, clay (less than 0.002mm). 

As the illustration below shows, each has specific traits that can be both good and bad depending on how prevalent they are in the soil.

Fortunately, nature has already figured out the best combination of these three soil minerals when it comes to growing plants, and we call this optimal mix “loam.” 

What is Loam?

Loam is a testament to nature’s engineering prowess. It is essentially the result of taking those three minerals and making their unique attributes work beautifully together. And since a picture is always the best way to illustrate complexity, here’s another image of that mix and how it all works:

So, while all five ingredients are critical to healthy soil, it’s the minerals and their unique structure that set the stage for everything else - air, water, organic matter, and microbes - to work together properly. 

For a moment, let’s pretend there’s no perfect loam recipe and mix minerals in different ratios to create a soil type, say a sand-dominant or a clay-dominant. 

Here’s what might happen as a result:

Healthy Garden Soil Grows Healthy Plants

Prioritising soil health can transform your garden into a biodiverse hub that supports a wide range of plant species and harbours insects, worms, and pollinators.

Keep watching this space for more blogs with tips to keep your soil healthy and garden flourishing!