The importance of soil

Soil is everywhere. There are seemingly endless amounts of it. We might ask ourselves what’s all the fuss about. If something as fundamental as oil really under threat? And why, in a modern society where we have all this technology at our disposal, is soil still so important? John Quinton is Professor of Soil Science at Lancaster University. And he’s an expert in soil security. John, can you tell us what the term soil security means? Well, Carly, I guess the thing about soils is they take so long to form. So a soil may take 10,000 years just to form 30 or 40 centimetres of soil. And that means that we need to think of them really as an unrenewable resource.

So if we damage soils, they’re not going to recover very quickly. So we have this concept of soil security, which really thinks about the kind of sustainable use of soils and protecting them for the future. And we’ve been starting to learn in this course already about why soils are important. And I guess one of the most important reasons is actually food. Yeah, sure. So soil really provides almost all the food that we eat. We stood here in this is lovely farm shop, and all the fruit and veg that we can see around us has being grown in soil.

Even the meat that are in the chiller cabinets behind us has been raised on fields with the animals grazing on the grass that is growing in the soil. So almost all the food that we eat is coming from the soil. And we therefore need to protect that soil for future generations. And the soil presumably is providing all the nutrients and the water. That’s right. So the plants that grow in this soil need nutrients, particularly nitrogen and phosphorus, from the soil. And they also need water. And soil stores around about 2/3 of all the fresh water on the planet. And that’s used by the crops that are growing in it. Well, water’s clearly very important.

So let’s go and have a look at some of the interactions between soil and water. Yeah. Let’s do that.

OK. So now we’re standing in this arable field. Let’s have a look at some of the soil and see how the water’s stored in it. So I just dig up a clod here. What you can see, Carly, is that the soil is actually a mixture of mineral material, organic matter, but also, critically, lots of pores. And we can see a big one just running down here. These pores are important for holding onto the water and supplying water and air to the plants that are growing in this soil.

So absolutely vital that these pore networks are maintained by the farmer within the soil management programme so that he keeps the water within the soil, but allows some of that water to actually run off into the ditches and keep the soil dry enough so that the plants don’t become waterlogged. And we’ve been learning about life in the soil. Presumably the water and air that are in those pores are very important for that as well. That’s right, Carly. The soil is packed full of microorganisms, invertebrates that are feeding on the material, the organic matter, within the soil. And they need a balance of water and air to survive.

When the soil becomes waterlogged, those organisms find it much more difficult to live within the soil. Even within an aggregate, just the size that I’m holding in my hand now, you might have more microorganisms than there are people on the planet. So this soil is quite dark in colour. Does that mean it has quite a lot of carbon stored in it? We hear a lot about carbon and climate change. So is that another service that this soil is providing for us? Yeah. Absolutely, Carly. These soils contain more carbon than is contained in all the forests and the atmosphere combined. So they’re absolutely vital for the carbon cycle. These soils here in the northwest are probably about 15% carbon.

That’s quite high, and that’s because here in the northwest, it rains a lot. it’s also pretty cold as well. And so bacteria and fungi don’t break down the carbon as quickly as they might in a warmer climate. And there’s also cultural reasons that soils are important. Yeah. This is one of those things that people don’t often think about. A lot of our buried treasure is actually beneath the soil’s surface. We find Roman mosaics or Viking hordes buried beneath the soil that’s been preserved there for many years. Many of the paints and the colours and the pigments that were used in the old masters’ paintings all came from the soil.

So actually, soils have cultural significance as well as being important for all the other services that we’ve been chatting about. So we have a lot of reasons why soils are important to us, even in this day and age when we have so much technology. But why do we need to be looking after the soils more than we already do? Well, we know that they form very, very slowly. And that’s one of the key problems for them. So they don’t recover very quickly. And they’re exposed to a wide range of threats, both at local and global scales. So what would the global scale threats be? So things like climate change are going to affect soils.

Rising temperatures can cause a faster decomposition of the organic matter. And so we lose some of that vital carbon that’s stored within the soil. There are issues with air pollution. The soils in the UK, actually, are just starting to recover after being acidified for the last couple of centuries from emissions from industrial pollution. That’s now come under control, and it’s actually a good news story for our soils as they begin to recover from that. And on a local scale, there’d be a whole range of different threats that would affect a farmer with a field like this one. Yeah, sure.

So particular problems for farmers are going to be things like soil compaction, so where they’re driving heavy machinery over the soil. If they’re unable to do that in ideal conditions, they can end up squashing the soil, compressing all those pores that we looked at earlier. They can also suffer from problems of erosion, so where we get too much water on the surface of the soil and that washes off and carries soil with it. And in dry climates, you might have problems with salts accumulating within the soil. Salinisation, which can poison the plants that are growing in the soil. A lot of your research is on soil erosion. Shall we go and have a look at one of your experimental sites?

Let’s do that now.