Dirt, mud, ground, earth… soil is without a doubt one of the world’s most important natural resources. It’s essential for growing the plants we eat, keeping our water clean, drawing carbon from the atmosphere, and is home to countless living organisms. It houses an underworld of fungi, insects, worms, and dead and decaying matter—all of which play a crucial role to support global biodiversity.

Simply put, without soil there would be no life! For our latest blog we are going to scratch beneath the surface of soil science so you can appreciate how incredible the ground beneath our feet really is. 

What is soil?

Soil is a mixture of organic matter and minerals which holds water, air, and microorganisms. It’s the loose top layer that covers most of the land on Earth, and is where many important processes take place. Healthy soil has three main properties:‍

• Chemical properties: The chemical processes happening in the soil, such as what nutrients are available, the acidity of the soil, salinity, etc. 
• Biological properties: These are the microorganisms and organic matter that lives in the soil, such as earthworms, mites, etc, plus their activity and by products.  
• ‍Physical properties: These are the characteristics of the soil that we can see, such as texture, soil structure, porosity, permeability, etc. 

All of these properties work together to produce rich, healthy soil that’s packed with minerals and great for biodiversity. For example, organic matter produced by plants and animals in the soil is broken down through various chemical processes, which is what’s called decomposition. This decomposition is what returns nutrients and minerals to the earth so that new plants can grow. This is why composting is popular with gardeners. Compost is made up of organic matter such as food waste and manure which is added to the soil to make it rich and fertile for growing plants, crops, and veggies.

What’s so special about soil?

Healthy soil has an abundance of beneficial organisms like microbes, organic matter and minerals. Microbes such as bacteria and fungi work to decompose organic matter, transforming it into nutrients which help plants grow and remove pollutants. Minerals like iron, potassium, magnesium, etc, ensure proper drainage and aeration of the soil. Healthy soil needs a good structure to anchor roots and permeability to allow water to move through it with ease. Soil has several very important ecosystem functions which we have already touched on, and is one of the world’s most valuable resources. 

• Soil is responsible for plant growth: In soil, plants set roots, which draw the water and nutrients they need to grow. The roots anchor them in place, and the soil provides protection from toxins.
• Soil regulates the water supply: Soil stores water that’s used by plants, and allows water to seep down into the groundwater. Contaminated water can also be purified as it passes through the soil.
• Soil for recycling: Soil is the planet's enormous recycling center. Waste and organic matter returns to the earth to create new life. 
• Home for life: Soil is a habitat for billions of organisms, from worms and insects to mycelium which produces mushrooms and fungi. 
• Soil can help us tackle climate change: Gasses are exchanged between the soil surface and the air. Oxygen and methane are absorbed while carbon dioxide and nitrous oxide are released. These chemical processes are what makes soil such a valuable carbon sink. 

What are the different types of soil?

When we talk about soil and soil health, we are not just talking about one kind of soil in one location. Soil properties and composition are different all over the world, and there are a number of characteristics that make them useful.

Sandy soil

Sandy soil is characterized by its loose, granular texture and large particles. It’s mainly formed from the weathering and disintegration of rocks, especially quartz. Due to its larger particle size, sandy soil allows more water to pass through which helps combat waterlogging. 

That said, this makes it less ideal for plants that need a lot of moisture to grow. Its fast drainage also means that sandy soil loses nutrients quickly. Root vegetables (carrots, potatoes), herbs, and certain types of drought-resistant plants like cacti and lavender enjoy sandy soil.

Clay soil

Clay soil is made up of very fine particles that are tightly packed together, which means that it retains water better than other kinds of soil. Clay soil is often heavy, sticky, and wet. This soil is valuable in dryer months because it retains water well, but is prone to flooding during heavy rains. 

Peaty soil

Peaty soil is loaded with organic matter, such as leaves and other plant material. It’s usually found in waterlogged areas like wetlands, which slows down the decomposition process. As a result, excess plant material builds over time. Peaty soil is very acidic, and despite being loaded with organic material, it tends to lack important nutrients like nitrogen and potassium. Only very specific plants can grow in acidic, peaty soil, eg. types of flowers such as rhododendrons and azaleas.

Chalky soil

On the other end of the pH spectrum is chalky soil, which is highly alkaline because it’s mostly made up of calcium carbonate or lime from underlying chalk or limestone bedrock. Chalky soil is often shallow and made up of larger rocks, which allows water to drain quickly, making it prone to drought. In general chalky soil lacks a lot of vital nutrients because of its alkaline nature and structure, making it less fertile and difficult to work with.

Loamy soil

Gardeners and farmers love loamy soil, because it provides a balanced mix of sand, silt, and clay. The well-rounded properties of loamy soil make it easy to work with, as it’s easy to dig and keeps roots in place. It has the perfect balance of drainage and moisture retention, which creates the perfect environment for organic material to thrive. All kinds of plants and vegetables love loamy soil, and it’s particularly sought after in agriculture.

What is soil degradation?

Soil degradation is one of the world’s most pressing issues, and it has had devastating effects on regions around the world. Simply, soil degradation is the physical, chemical and biological decline in soil quality. It can include a lack of organic matter, structural integrity, or changes in salinity, acidity, or alkalinity brought about by flooding and pollution. Today, around 33% of the world’s soil is moderately or severely degraded. The areas where soil degradation is the most prevalent are regions affected by poverty, highlighting the strong relationship between soil quality and food security. 

One example of how human activity has caused major soil degradation is Africa’s Sahel Region. Rising temperatures and drought has led to what’s called desertification, where once fertile land turns into desert, causing food insecurity, loss of livelihoods, and displacement of communities. In response to this, the Great Green Wall Initiative was proposed to plant a gigantic ‘green front’ to act as a tree buffer to contain the expanding desert. In another part of the country, Kenyans are also trying something different to tackle soil degradation. Justdiggit uses a simple yet powerful method to restore the land: by digging half-moon-shaped water holes. These so-called “bunds” capture rainwater and prevent soil erosion. Native grass seeds are added, which now have all the water they need to sprout, kickstarting the regreening process.

Maintaining soil health is vital not just for agriculture but also for sustaining ecosystems and fighting climate change. Healthy soils support plant growth, prevent erosion, and sequester carbon, making them a valuable resource. Whether for farming or gardening, investing in the care and rehabilitation of soils ensures food security, environmental stability, and the overall health of our planet.