Fascinating Soil Facts: 23 AMAZING Facts About Soil
We’ve already discussed some of the reasons why soil is important on this blog, but there are so many interesting facts about soil – it truly is one of the most underrated ecological systems on earth!
Here’s our list of 23 of the most fascinating soil facts – everything you ever wanted to know about soil!
The soil is the great connector of lives, the source and destination of all. – Wendell Berry, author of The Unsettling of America
1. Soil is Not Dirt
One of the most fundamental things to know about soil is that it is not dirt.
Dirt is an inorganic material made from broken-down rocks that primarily consists of minerals like iron, calcium and magnesium.
So, what is soil made of?
Soil, on the other hand, is dirt + water, air and organic material. It is the living layer between the atmosphere and bedrock.
2. Soil Consists of Many Layers
Soil is a really complex material. Let’s look again at what soil is made of: soil is composed of about 45% minerals and broken rock (the dirt mentioned above), 25% water, 25% air and up to 5% organic matter (decaying plant matter and living things like fungi, bacteria, worms and other insects).
Soil is also usually described as having 5 or 6 layers: an organic layer (filled with decaying plant matter); topsoil (where we find plant roots and living organisms); subsoil; parent material (your basic dirt layer); and finally, bedrock (the floor of the world).
Topsoil is where the action happens. It is the most critical layer of soil, where we grow our food, and where worms and other critters feed on organic matter, turning it into food for plants. Topsoil is vulnerable to erosion, though, and can be lost when soils are degraded.
Together with the subsoil and parent material, topsoil forms part of the rhizosphere where plants communicate with each other! Isn’t that an interesting fact about soil?
3. There are 70,000 Different Types of Soil in the US Alone
That’s right, there is not just one type of soil! Soil type and quality varies a lot based on where you are and what the climate is like. Soil types are generally classified based on how much sand, silt and clay can be found in them. Different types of soil, including garden soil, differ in colour, texture and productivity.
4. Soil is Alive
Soil seems like it is inert, but it is actually teeming with life. In fact, healthy soil is considered a living system!
5. There are More Living Organisms in 1 Tbsp of Soil Than There Are People on Earth
Is your mind blown?
This is definitely one of the most interesting facts about soil.
That’s in terms of the number of individual organisms, but there is also a staggering amount of biodiversity in the soil. In fact, soils are one of the most biodiverse ecosystems on the planet!
Here are just a few fun facts about the number and variety of organisms living in soil according to the USDA and other sources:
1 tsp of soil contains between 100 million to 1 billion bacteria
1 g of 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.
The top 6 inches of one acre of soil contains as much as 20,000 lbs of total living matter.
1,400,000 earthworms can be found in just one acre of farmland.
6. Earthworms “Eat” 15 Tonnes of Soil Per Acre Per Year
Along with other soil organisms, earthworms feed on organic material in soil, converting it into nutrients that plants need to grow. They also have a physical effect on the soil: as they wriggle and move through the ground, their motion breaks up the clumps, keeping the soil well aerated and better able to absorb water.
7. Amazing Facts About Soil: Soil is Essential to Life
Despite being at the very bottom of the food chain, soil is the cornerstone of all life. Soil is responsible for providing plants with everything they need to grow: food, air, water and a “home” for their roots. And we and other animals ultimately rely on plants for our own health and wellbeing.
Soils support 95% of all food production, and agriculture is the only industry considered “essential”. Is that news to you?
8. Soil Can Die
Living soils exist in a precarious balance and can “die” like any other living system. Many conventional agricultural practices – like the overuse of chemical fertilizers and pesticides – disrupt this balance and create unhealthy soil. In addition to being less productive – thus requiring ever more fertilizers – degraded soils are vulnerable to erosion which wipes away the productive topsoil layer.
This is what happened during the 1930s Dust Bowl in the United States. Decades of poor land management practices killed the living networks that had kept the soil alive and productive, so that when severe droughts hit, strong winds blew away as much as 75% of the topsoil, leaving nothing but parched earth behind.
9. Soil Facts: It Takes At Least 500 Years to Form One Inch of Topsoil
Soil is considered a non-renewable resource, making it even more precious – and something we ought to take care of!
Soil is formed through a geological process that slowly transforms bedrock into the living matrix we know as soil. The whole physical, biological and chemical process can take tens of thousands of years – way beyond our human timescale.
Unfortunately, erosion can wipe away a full centimetre of precious topsoil in just one year.
10. We Need Soil for Clean Drinking Water
Soil is Earth’s natural water filtration system. Surface water trickles down through the various soil layers where it is filtered of chemicals, dust and other contaminants in the process. In this way, by the time it reaches and collects in underground aquifers, the water is pure.
Soil’s natural water filtration is also great from an economic standpoint. What costs about $1-1.5 billion for the Catskill Watershed to provide clean water to New York through natural soil filtration processes would cost as much as $6-8 billion to build a water filtration plant, plus another $300 million in annual operation and maintenance costs. That’s an astounding savings (and a really fascinating fact about soil)!
11. 0.01% of the Earth’s Total Water is Stored in Soil
Soil can store up to 9200 tonnes of water per acre. Storing water in soil helps to regulate water flow during rainfall and can help prevent or reduce flooding.
This is largely thanks to the organic matter found in soil. In fact, the United States Department of Agriculture Natural Resources Conservation Service (NRCS) found that a mere 1% of organic matter in the top 6 inches of soil could hold as much as 27,000 gallons (over 100,000 L) of water per acre.
Essentially, all life depends upon the soil… There can be no life without soil and no soil without life; they have evolved together. – Dr. Charles E Kellogg
12. More Fun Facts About Soil: Most of Our Antibiotics Come from Soil
One of modern medicine’s most important life-saving advances was the discovery of antibiotics used to treat bacterial infections. And – amazing soil fact – almost all of these antibiotics come from soil microorganisms!
Moreover, the soil may be integral to helping us maintain an optimal gut microbiome – and help fight depression. This is why authors Jack Gilbert & Rob Knight argue that exposing our kids to dirt and germs is a good thing in their book, Dirt Is Good: The Advantage of Germs for Your Child’s Developing Immune System.
13. That Magazine Page is About 70% Soil
Here are some unexpected soil facts: Soil fillers are used to create the glossy pages found in many textbooks and magazines. As a result, as much as 70% of their weight can be attributed to soil!
14. Soil Degradation May Be to Blame for the Collapse of Some Ancient Societies
Archaeologists believe that the collapse of some ancient civilizations – including that of Harappa in the Indus Valley, and the Mayans in Central America – was a direct result of mismanagement of their soils.
15. 1/3 of Today's Soils Are Degraded
It seems like we haven’t learned from the experience of the Dust Bowl, because almost everywhere the same conventional farming practices are in place which are destroying soil’s living ecosystems.
The UN’s Food and Agriculture Organization (FAO) estimates that a whopping 1/3 of all soils are moderately to highly degraded. This is due to things like chemical pollution and nutrient depletion which kills the soil ecosystem, leading to salinization, acidification, erosion and/or compaction of soils, which in turn reduces soils’ productivity. According to IDS, soil is being washed away at a rate 10-40 times faster than that at which it is being replenished. This is real cause for alarm.
Solving these soil problems must be at the top of humanity’s list of priorities. If the Soil Health Institute’s projections are correct, by the year 2060 we will ask our soils to produce as much food as we have consumed in the last 500 years combined. That’s an astounding feat.
The nation that destroys its soil destroys itself – Franklin Roosevelt
16. The World’s Soils Contain 2500 Gigatons of Carbon
That’s nearly 80% of ALL carbon found in terrestrial ecosystems – more than 3 times as much carbon as is found in the atmosphere (800 GT), and more than 4 times as much as is stored in all living plants and animals (560 GT). Only the ocean has a larger carbon store!
Is that not one of the most incredible facts about soil?
17. More Than 1/3 of All Greenhouse Gases (GHGs) Released Since 1850 is Due to Land Use Changes
Soil is naturally a carbon sink, so when it is disturbed, it releases carbon into the atmosphere. Intensive land-use change since the mid-19th Century that disturbed soil is therefore responsible for a significant portion of GHG emissions since then.
These land-use changes include clearing natural, vegetation-covered environments for logging or to create cropland or grazing pastures.
18. Between 10% and 14% of Total Global Carbon Emissions Come from Industrial Agriculture
Erosion, soil disturbance, nutrient depletion and the harvesting of biomass resulting from conventional industrial agricultural practices have led to a reduction of 30-50% of carbon in most cropland’s topsoil, as compared to its natural state. Much of this carbon has been released over time as carbon dioxide.
The intensive use of machinery and chemical fertilizers and pesticides also contributes to agriculture’s ongoing carbon footprint.
19. Soil Has a Significant Role to Play in Climate Change Mitigation
Here’s a fun fact about healthy soils: Well-managed soils can help mitigate climate change by sequestering carbon out of the atmosphere, and store it.
Scientists estimate that the world’s degraded and agricultural soils have the potential to restore 50-66% of the total soil organic carbon (SOC) lost. On an annual basis, it is estimated that regenerated soil could offset 5-15% of global fossil fuel emissions.
Regenerative agriculture techniques – including no-till farming, the use of cover crops, silvopasture, nutrient cycling and more – can be used to draw carbon out of the atmosphere and into the soil, making it a key part of climate change mitigation efforts. The added benefit is that these techniques also result in healthier, more productive soil which simultaneously addresses food security issues – and helps the farmers’ bottom line.
A mere 2% increase in the carbon content of the planet’s soils could offset 100% of all greenhouse gas emissions going into the atmosphere. – Dr. Rattan Lal
20. Farmers Can Increase Soil Organic Matter in as Little as 3 Years
The benefits of regenerative farming are very attainable. With dedicated practice, most farmers can increase the soil organic matter content in their agricultural soils in just 3 to 10 years.
21. Soil Health Boils Down to Two Major Principles
1. Disturb the soil as little as possible. This means, leaving land untouched wherever possible, and using no-till farming practices in order to keep vital ecosystems intact.
2. Keep soil covered as much as possible. When it comes to cropland, rotate fields, and plant a diverse range of crops, all year round. Plant diversity improves biodiversity in the soil, and the use of cover crops ensures that the soil remains covered.
22. We Still Have So Much to Learn About Soil
Think we’ve figured out everything there is to know about life on Earth? Far from it! There are still so many things to know about soil. Only about 1% of all microorganisms living in soil have even been classified. If we already derive so much benefit from that 1%, think about how much more there is to learn from the other 99%!
For one thing, we are just starting to learn about the fascinating world of plant communication. Trees are interconnected by a network of mycorrhizae found in soil. These mycorrhizae have a symbiotic relationship with tree roots, transferring not only water and nutrients between the trees, but also sending chemical messages between them!
Researchers are just starting to understand these inter-tree communication networks – a soil-based internet, if you will – but signs are already pointing to them being critical for forest ecosystem function. How’s that for a fun fact about soil?
23. Soil Has its Own Annual Day of Celebration!
Are you ready to celebrate the importance of soil? Join the FAO in honouring our life-giving soils on World Soil Day every December 5th.
Facts About Soil: What You Didn’t Know About the Ground Beneath Your Feet
There are so many interesting things to know about soil. We hope you have enjoyed these facts about soil, and even learned something! Test your new-found knowledge with this soil quiz.
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.
Soil Science Society of America