Why is Soil Important?
Have you ever stopped to think about what’s going on beneath your feet? Most of us probably have not considered the importance of soil, but the truth is, it’s pretty essential. Why is soil important? Healthy soils provide nutrients to plants, filter water and can even store carbon. In fact, soils are increasingly being studied for their role in climate change mitigation.
Keep reading and we know you’ll ‘grow’ to love soil!
What Is Soil?
First of all, let’s clear up a common misconception: soil is not dirt. We tend to use the two words interchangeably, but they are really not the same thing. Dirt is mostly made of broken-down rocks. It is inorganic and consists mainly of minerals like magnesium, iron and calcium. Dirt plus water, air and organic matter (think: bacteria, fungi, worms and insects) equals soil.
And unlike plain old dirt, soil is fundamental.
The ground can be divided into five basic layers:
Organic Layer – this is a layer of decaying leaves and plant matter that covers the soil and provides the nutrients to the layers down below.
Topsoil – this is where the action happens. Topsoil is filled with organisms and organic matter and houses most plant roots.
Subsoil – this layer is full of iron and clay, elements whose origins were also in that organic layer on top.
Parent Material – this is your basic dirt, the rocks that have broken down over millennia. Deep tree roots can reach even this far!
Bedrock – a solid layer of rock, basically the floor of the world.
The middle three layers form the rhizosphere, where plant communication and so much more happens.
Soil’s importance to life cannot be overstated. Along with the plants that grow in it, soil is the basis of the complex soil food web, critical to life. And there isn’t just one kind of soil, either. The exact composition of minerals, water and organic matter can vary from place to place – and the type of soil you have impacts what you can grow. It’s good to get to know your soil!
What Does Soil Do?
What doesn’t it do?! Soil does so many things for us, that’s why soil is so important! Here is just a taste:
Soil provides a home for plants. The soil anchors plant roots and provides them the necessary nutrients they need to grow.
Soil regulates our water and helps keep it clean. It filters and retains water, and regulates water flow which helps prevent flooding. Soil’s water filtration capacity is what keeps our groundwater free from pollutants, too.
We build with soil – and on it. Soil is used as a basic construction material – from mud brick houses to the porcelain used to make fine ceramics. Soil is also essentially our foundation for everything, from highways to buildings, and is where we house solid waste.
It provides a habitat for billions of organisms. This is critical to biodiversity. In fact, more than 25% of the planet’s biodiversity is found in the soil!
It is the foundation of our agroecosystems. Without it, we could not produce feed, food or fuel!
Let’s look at some of these soil functions a little further.
Why is Soil Important for Plants & Agriculture?
First and foremost, soil is critical for the wellbeing of plants and plant growth.
Root System Support
For plants, the soil is their home. Just like the foundation of a house, healthy soils support plant roots and help ensure that they grow upright. Just which and how many nutrients are present depends on the type of soil.
Plant Pantry
What are we going to eat tonight? The soil acts as a plant’s food pantry: it stores and releases the essential nutrients and minerals a plant needs to be healthy, to grow and produce their flowers, seeds, fruit or vegetables. This is the basis of the soil food web: sugars and organic matter are eaten by bacteria and fungi; nematodes and protozoa eat the bacteria and fungi; and plant roots absorb the nutrients excreted by the nematodes and protozoa during their digestive process.
Water Storage
Soil also stores water for plants, providing them with continual moisture and helping to transport nutrients to the root system. How much water soil can hold depends on the type of soil (clay holds more than sandy soil) and also the amount of organic matter. According to the USDC, “every 1% increase in organic matter results in as much as 25,000 gallons of available soil water per acre.” (See this quote expertly explained by the NRDC). Soil can also filter harmful contaminants away from plant roots.
Oxygen Provision
Soil is necessary to provide oxygen to insects, microbes and plant roots. Oxygen gets trapped between soil particles where roots can use it to break down sugars in the rhizosphere and root microbiome, which they then pass on to the plant, providing the energy it needs to grow.
Protection from Erosion
And, soil protects the land from erosion. This has to do with the support soil provides to plant roots. Without it, the ground would simply wash away during heavy rains, taking trees and plants with it.
Weed Control
Arguably the gardener’s favourite soil function, soils help control weeds, pests and disease. This ultimately results in healthier plants and better crop yields – even without the use of pesticides and fertilizer. So nurturing soil health in your garden is the starting point for good lawn care (and if you want to know how good your soil is, you can get someone to do a soil test for you!)
Other ways to nurture soil health include composting your food waste and adding it to your soil, or the bokashi method. Haven't heard of bokashi before? Read all about it in this article about bokashi vs compost. Both methods work by adding organic matter and nutrients to the soil, essentially feeding it.
Temperature Modification
The soil acts like insulation, too, protecting root systems from changing temperatures and extremes of heat and cold.
If you're a gardener take note: All of these important soil functions are multiplied when you add mulch to your garden. Click here to read all about the advantages of mulching your garden!
The Importance of Soil for Animals
When we talk about soil and animals, we’re usually thinking of small creatures: insects, earthworms, millipedes, centipedes, beetles and spiders. These creatures rely on soil health quite directly for their survival. And when they die, they become food for the abundance of soil microorganisms.
But actually, all animals, big and small, depend on the soil for food and oftentimes shelter, too. Burrowing animals make their homes in the soil, while herbivores graze on grasses and other plant matter which need the soil to grow. And carnivores in turn consume the herbivores.
The quality of soil is directly related to biodiversity. Beneficial soil microbes are nature’s hidden helpers, forming synergistic relationships with plants. Scientists at the USDA have found between 100 million and 1 billion bacteria alone in a single teaspoon of healthy soil. Put another way, one gram of healthy soil can contain as much as 75,000 species of bacteria; 25,000 species of fungi; 1000 species of protozoa; and several hundred species of nematodes. They help break down organic matter, extracting from it vital nutrients the plants can use.
“To forget how to tend the soils is to forget ourselves” - Mahatma Gandhi
Soil is Important for Humans, Too!
As animals ourselves, it should be obvious that soil’s importance extends to humans, too. But let’s go a little deeper and a look and some of the obvious and not-so-obvious ways in which soil is beneficial for people, whether directly or indirectly.
Soil Provides Food
This is one of the obvious ones. Healthy soil grows healthy and abundant plants, which we then eat. (Because we call them by different names, people forget that the world’s top staple food products – wheat, rice, corn and potatoes – are all plants. Read more about the diversity and fascinating history of potatoes in Peru.)
As we learned above, soil not only provides a place for food to grow, but is also the basis of the food web that is necessary for plant health.
Soil Filters Our Water
In order to have clean drinking water, we need soil. As it flows through the layers of soil, surface water is filtered of chemicals, dust and other contaminants so that it is clean when it reaches underground aquifers. That’s why underground wells are one of the cleanest sources of water around.
Not only is this great from a health standpoint, but also from an economic one: according to the Soil Science Society of America, the cost of the Catskill Watershed to provide clean water to the city of New York through natural processes is about $1-1.5 billion. Compare that to the $6-8 billion it would cost to build a water filtration plant. Thank you, soil!
Our Antibiotics Come from Soil!
One of the most important advances in modern medicine is the discovery of antibiotics to treat bacterial infections. Guess where almost all of our antibiotics come from? The soil!
Still Wondering Why Soil is Important? Here Are Some More Reasons!
We Build with Soil
Soil not only provides the support for our various construction projects – from roads to bridges and railways – but is also an important source of raw materials. We tend to think of soils as an old-fashioned construction material, as in old wattle-and-daub or adobe brick houses, but even modern-day bricks and ceramics find their raw material in soils.
Healthy Soil Helps Regulate the Climate
You might not realise this but soil is integral to mitigating the impacts of extreme weather events (like, by helping to prevent erosion during heavy rain) and…it also helps to regulate Earth’s temperature.
As a result, healthy soils have an important role to play in protecting the planet from climate change. Currently soil removes about 25% of global fossil fuel emissions from the atmosphere each year. We talk about soil health and carbon sequestration here – how soil sequesters carbon, and what we can do maximise its potential.
Soil is Important Because it is so Precious
Last but not least, soil is a non-renewable resource. We can lose a centimetre of soil in one year thanks to erosion – but it will take hundreds, even thousands, of years to build that centimetre back.
Given all it does for us, our fellow beings, biodiversity and the planet, soil is truly a resource that we should treasure.
Why Is Soil Important? The Final Analysis
If there’s one take-away from this article, it’s that you should not take the importance of soil for granted (but if you’re not yet convinced, be sure to check out these fascinating soil facts!).
Dirt may seem so inconsequential compared to everything that goes on above-ground, but it really is the backbone of all life on earth. So what can we do to celebrate soil’s importance for life? Well, for one thing you can be sure to celebrate World Soil Day on December 5th!
World Soil Day was created by the United Nations in order stress how important soil is for the environment, and for life. It is also a day to spread awareness about the importance of soil health and protecting this indispensable natural resource.
The next time someone asks you – why is soil important? – you’ll be able to give them an earful – and help ‘plant the seeds’ about soil’s importance in another mind!
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About the Author
Sarah has over 10 years’ experience working with indigenous communities in Peru. She travelled to Peru for the first time in 2006, where the culture, the people and the landscapes ignited her passion. Sarah has travelled extensively throughout the country as well as the rest of South America, and is especially familiar with the Cusco and Sacred Valley areas. After completing her law degree at the University of Victoria in 2017, Sarah now splits her time between Cusco, Peru and Kingston, Ontario.
