Soil FAQs

There Are Hundreds of FAQs About Soil & The Answer To Many Soil FAQs Are Given Here. From What Is Soil & How Is Soil Formed To Decomposition & Soil’s Role In Carbon Capture, You’ll find Soil Answers Here.

I’ve been gathering Soil FAQs for years. It started when, as a student, I studied pedology. Many people will tell you pedology is the same as soil science, but it isn’t. It’s one half of soil science, the other is edaphology .. more on that later. Today I’m interested in soil from two points of view. The structure of soil and the life in soil. At a very basic level I differentiate between pedology and edpahology as being about the dead bits of soil and the live bits of soil. The fact is, soil is alive in the sense that it is full of life. It’s said that a teaspoon of soil will contain 40 billion bacteria. Putting this in context, the total population of all the humans that ever lived, is around 100 billion!  

Here Are My Favourite Soil FAQs

 

Soils and Carbon Storage

With global warming carbon is big news. There’s too much CO2 in the atmosphere and more is released as we use peat. But soil could be the answer.  Soil has huge capability as a carbon sink. It can store more carbon than the atmosphere and all the worlds trees and plants combined. So rather than just focus on planting another tree perhaps we should think about how we can store more carbon in the soil. In the UK our soils hold around 10 billion tons of carbon. But it decreases each time we plough, dig or rotavate the soil. So any technique that decreases soil disturbance is good. That’s one of the reasons I’m a firm advocate of No Dig (the others include better weed control, better moisture retention etc.)  

What is Soil?

this is the most common question I get asked and the one that so many people get wrong. The biggest error in this context is to describe soil as dirt. It might make you dirty, but it isn’t dirt. Soil is a complex mix of things that can be dead or alive. Only when you get it on your hands or, as I did as. a child, on your knees can they be said to be dirty. That is so different to being dirt (which is a terrible Americanism). To describe soil in more detail I’ve written a whole article on What is Soil? Click on the link below to discover more.

What is Soil?

 

How Important Is Soil?

Virtually everything we eat has involved soil somewhere in its production. From the obvious ones like vegetables that usually grow in the soil. (Hydroponically produced food is an exception, but not much food is produced this way). To things like eggs that are produced by hens that feed on grain that has been soil grown. Plus the cheese we eat that has been produced from milk that came from grass or grain fed cows. Even wine and beer start with growing crops as does sugar and tofu! There are few things we eat where the soil isn’t involved somewhere along the way. Then there’s building materials, bricks are formed from clay which its a type of soil. And timber grows in soil. Soil also helps with our waste. Waste from farm animals and humans are often ploughed into the soil to improve fertility. And soil “caps” are put over waste tips to contain the methane they produce (much of which is then burnt to prevent it damaging the ozone layer. Without soil life earth would cease. You and I depend on soil for our very existence.  

Is Soil Alive?

Yes and no, parts of it are inorganic materials, such as powdered rock, but it also contains billions of bacteria, fungi and other living organisms. So though technically the soil itself isn’t alive it does act as it it were. So I prefer to think of it as a living organism, even though I know that this is technically incorrect. There’s a whole paragraph on whether soil is dead or alive in the above post.  It mentions many of the parts of the soil that are alive, from bacteria to fungi. But we should also recall that many new soil bacteria and fungi are being identified and classified every year. So it’s likely that many millions are yet to be catalogued for the first time. And some of the inhabitants of soil are very strange. Take tardigrades. Discover in 1733 by  German pastor, Johann August Ephraim Goeze, they are minute organisms, just visible to the human eye, that are capable of cryptobiosis. This is an extended form of extreme “hibernation” where their metabolism slows to around 0.01% of normal or lower and an organism can survive for thousands of years. In fact they can survive the extreme cold of space and high radiation doses that kill all other life forms. They are virtually indestructible, and live in our soils! A far as we know tardigrades have been around about half a billion years. At least, that’s on Earth. (But Star Trek Discovery enthusiasts will know about how they are portrayed as travelling through a intergalactic hypha network using a spore drive).  

What Are Soil Horizons?

You’ve probably heard the term topsoil and bedrock. They’re just two of the six soil horizons that virtually all soil has. Think of them as layers of soil in a soil “cake”. In order from the top they are …

Organic Layer

Often called the O horizon this layer is made upon of organic material such as lawn thatch or fallen leaves. In woodlands it can be quite thick, on cultivated soil it will be very thin or even absent.

Topsoil

This is the bit where most of the plant growth takes place. So the more you have the better. It can be anything from clay to sandy in nature but is best when it contains a good proportion of organic matter, bacteria, fungi and other micro/macro fauna. It is derived from the parent material and will contain a mix off minerals.

The Eluviated Layer

This is a layer where there is a concentration of sandy and silt particles due to the clay, minerals and organic matter having been leached out. It is absent in some soils, or very thin, but where it occurs it is rich in quartz and other materials that are resistant to breakdown. Eleuvaiated soils are most common in old soils such as as woodlands and forests. The E layer is often grey or quartz  

Subsoil

Subsoil is the B layer in the soilIt is often mineral rich as it contains the minerals leached down from the eluviated layer and above!

Parent Material

The parent material is designated the C horizon and is the level from which the layers above are being derived.  

Bedrock

This is the R horizon and consists of the underlaying rock such as basalt, granite, sandstone or limestone. It is not soil but the most basic layer from which soil is ultimately produced over many millennia. On occasion, the bedrock is uncovered, which the rock erupting through the surface. In Devon we see it erupt as the tors on Dartmoor. Similar rock protuberances are also seen in other parts of the country, eg on Bodmin moor, in the Pennines etc. In places such as at Cragside in Northumbria the rock has led to the place name.  

Soil Horizon Exceptions

Not all soils consist of all six layers, though many do. And some have no horizons except the “topsoil”. For example the the Fens of Cambridgeshire are often our peat. It acts as both topsoil and the organic layer but is not derived from rock. It is formed from anaerobically decaying organic matter laid down over hundreds of thousands of years. The silts of Lincolnshire are another exception. I’m told they were laid down as a sediment by huge rivers long before the English Channel was created.  

What is a Soil Profile?

A soil profile is the vertical arrangement of soil horizons. It is typically seen where a stream or river cuts through the soil, where a trench is dug or where a landslip occurs.  

Here are links to my previously written Soil FAQs

 

Soil Carbon, Organic Matter & Nitrogen Balance

Soil, Fertilisers & Plant Nutrients

What Are The Main Types of Soil?

DIY Soil Testing For Soil Type, Structure, Compaction & pH

What is Soil?

What Are The Main Types of Soil?

 

Soil Porosity: What Is It, Why It Matters, Improving Soil Porosity