The story of soil

Robyn Williams: And now Mr Soil himself, also in Tasmania, often on SBS TV cooking and also on his farm. Matthew Evans, as you may know already, is driven by soil and is here to tell us why.

Matthew, in my hand I have a jar, it contains the soil of my particular area where I'm sitting at the moment, on the south coast of New South Wales. How close do you think it might be to the soil in your back garden? If you were to go out and get another jar and stick your soil in it, would there be the same?

Matthew Evans: Look, they'd be similar in lots of ways. I guess the proportion of rock would be similar, so 95% of your soil will probably be crushed-up rock, so it would be sand, silt and clay which are different grades, essentially, of crushed up rock. My soil is very silty probably compared to yours, you are probably a little bit more sand and clay. We've got a lot of silt, we are in the valley floor, that's the main difference. So 95% of both of our soil is going to be crushed up rock, but the proportions of sand, silt and clay are different. The other 5% of the dry mass of soil is hopefully organic matter, so things that used to live or things that are currently living.

Robyn Williams: Living things, billions of them, even in a handful.

Matthew Evans: Yes, some estimates put it that you can have more living things in a teaspoon of healthy soil then there are humans on the planet, up to 10 billion living things, and kilometres of fungal hyphae that define fungal threads in a tiny, tiny amount of soil. And I think this is why soil is a little bit underrated and undervalued because most of what exists in soil that gives it life, that makes soil not dirt, because dirt is just the crushed-up rock bit, we can't see it, we can't just look at soil and go, oh, there's a nematode, there's some protists or archaea, we have to trust science to find the living nature of soil.

Robyn Williams: In your travels, talking to young people especially, how many people in Australia know what you've just said?

Matthew Evans: I would guess it would be fewer than 1%, and it kind of scares me because about 1% of us are farmers and a lot of people have home gardens. And so a lot of people probably grow things and maybe don't realise that there is this living component of soil and that plants don't eat dirt, they need things from the crushed-up rock, but most of the time they can't get those things unless there is life in the soil that makes those things bioavailable, available in a form the plant can take up.

Robyn Williams: I must say, the picture you gave of where that soil comes from, you know, the broken-up rock, how do you break up rock? Well, you had a very violent Earth in the beginning which was boiling hot, and then one of the things that I had forgotten, practically, millions of years of driving rain non-stop. Imagine!

Matthew Evans: I know, worse than the UK, worse than Tassie in winter, it just rained for centuries. It would have been pretty miserable. There were no plants and there were no animals around. There were some bacteria possibly, microscopic single-celled organisms. But there was no one around to whinge about it or to report on it, except in historical terms we do it now.

Robyn Williams: And then of course you've got the cycles which developed over 3.5 billion years where complex life has existed, and you've got this cycle of the growth of plants, the falling of leaves, the millions of creatures in the soil of course which decompose things. Incredibly complex cycle, that we interfere with at our peril. And when I think of some of the projections they've got for farming, it's not simply monocultures where you've got acres and acres, or whatever you call them these days, of one crop, but a gigantic warehouse almost as big as a small town where you've got one crop and you've got artificial systems. Do you think that is the future of agriculture really?

Matthew Evans: No, I don't. I address this in the book, and we are not trying to blame farmers for trying to grow food to feed the world, but I think we've made some really big historical mistakes and miscalculations. I don't think anyone has gone out to bugger up the soil that grows the food that feeds the world. So soil wants things that we don't necessarily want. So, what soil wants is diversity, it wants a diversity of green living things in it all the time because those green living things feed that underground ecosystem. But farmers just want maybe a single thing. And over time we've wanted bigger farms growing more of that single thing. So we used to grow a lot more variety of crops than we do now and we used to rotate those crops. So even if you had a single field of wheat, say, you might rotate it with some kind of legume, a pea, and then maybe put some triticale or some sorghum or barley or something else in. And every plant takes something from the soil and every plant gives something to the soil. When we just grow a monoculture, we just take, take, take and we never give back to the thing that gives so much to us.

Robyn Williams: Which brings in carbon. Now, you've got lots to say about carbon and putting it back into the soil, you talk about biochar and various other methods for doing it, and this is being controversial, we've had on The Science Show many times some people claiming that you can put carbon in by doing various things. What is your line? How do you think we can best put carbon back into the soil productively so that it stays there?

Matthew Evans: Biochar is an interesting thing. That's essentially a form of charcoal. They found in various parts of Africa and in the Amazon it had been buried by humans in the soil and it created phenomenally fertile soil, so the charcoal itself has the capacity and it's very porous so it can hold nutrients, it can be a hiding place for the underground life. It's a very useful thing.

I guess the single best way to store carbon in soil is how nature intended, and that is when a tree or a shrub, a forb, when they photosynthesise, they take carbon out of the air and they use that carbon, using sunlight and water, they make carbohydrate, they make sugar out of thin air. It's a miracle, an absolute miracle that they can create their own food out of thin air. You and I can't do it, and neither can that underground ecosystem.

So what the plant does, because it needs the underground ecosystem, it takes some of those sugars, about a fifth, sometimes up to a half of their sugars they actually dribble out into the soil to feed the underground ecosystem. So a plant is essentially a carbon pump, pushing carbon not just into its structure but more importantly pushing that carbon into the soil where the underground ecosystem then stores that soil in short and long-term methods. Carbon is in a cycle, we are not just storing it, we are using it in the cycle, and we can be storing more carbon in the soil and growing more food and more nutrient-dense food if we work with plants and not against them.

A lot of farming at the moment seems to be about killing things that want to live and trying to make things live that want to die, and that's why it can be hard to grow things in certain climates in certain soils, so we are always fighting against the weeds and trying to nurture the things that are struggling to live. But if we try to work with natural cycles, we can store way, way more carbon in soil much more simply than having to make charcoal, truck it, make compost, truck it. Those things are good, they are great, they work, but there is another way and that is using a living green plant to do what it's supposed to do which is suck down carbon out of the air, store it in soil. We want carbon out of the atmosphere, and we want it in soil because it does beautiful things, it creates a home, it creates a food, it creates soil structure. It's brilliant for soil and it's not very brilliant in your oceans and in your atmosphere.

Robyn Williams: Are there many farmers in Australia actually doing that carbon experiment well?

Matthew Evans: Look, we had the first person in the world to be paid by the government to store carbon in soil, as opposed to just storing it in trees, that kind of thing, and there is a scheme to encourage that. Yes, there are people all around the country doing that really well.

It's a complicated system because it involves ecosystems, and you've got not only this amazing subterranean, living, breathing super-organism which is the soil ecosystem, but you've also got to deal with the plants, feed it, and the animals that walk over the land or fly over the land.

So they are complex ecosystems but there are brilliant people all over Australia and around the world who are storing carbon in soil and growing crops for humans to eat. Because the important thing to remember is we can let the whole world go back to a forest, we just won't feed many people. We will store lots of carbon, great, but if you want to feed lots of people, we have to give soil what it wants so we can get what we need in the long-term.

Robyn Williams: But do we get enough of what we need to make money? In other words, do you lose money by putting carbon in there, as you describe?

Matthew Evans: Yes, there is a transition period, and farmers are businesses, so farmers don't want to bugger up soil but they also have to run a profitable business, and it can be a difficult transition and it depends on where you are as to what that system is and how you store carbon in soil.

But the good thing about organic matter in soil is food for your plants, you can store water better, and this is the miracle thing, if you can increase your soil carbon by a couple of percent, you can store an extra 16 litres of water per square metre in the soil, so you don't have to pump it in from irrigation, you don't have to have it stored in a dam, you don't have to rely on rainfall. You store water in the soil by having more carbon in soil.

So you've got food, you've got drink, you've got better structure, so you've got air in the soil by having carbon in soil. So pretty much it's only a good thing for farmers in the long run, but there can be a transition cost in terms of yield. And farmers sadly aren't paid to restore soil, they are paid on kilograms per hectare.

Robyn Williams: And a moist soil keeps the worms happy, does it not?

Matthew Evans: Charles Darwin's last book…I had never realised this, Charles Darwin's last book was on worms, and I think what's beautiful about that is he went from the big picture, you know, what's happening with these incredible species in the Galapagos, wherever, and then looked at what's happening under his feet; why are rocks disappearing into the fields in the paddocks on his property in the UK? Why are they disappearing? He was trying to work out what it was, and he found it was worms, worms moving soil around, doing the work of what it would take an enormous amount of diesel to do but doing in a way that doesn't ruin soil, actually aerates soil, fluffs soil up. What comes out the back end of a worm is essentially a plant superfood at the same time. So worms, what little heroes they are!

Robyn Williams: Yes indeed. Did Charles Darwin have a compost bin, do you think?

Matthew Evans: I reckon he did, but composting, it was about 20 or 30 years later that someone came out with a way of coding composting and making it so everyone understood it. But I think everybody composted. We call it humanure now but essentially what comes out the back end of us, all around the world people were composting that 150, 200 years ago, a lot of people still do. We are all only temporarily not soil, so they take part of the nutrient cycling that used to be in the system, instead of flushing it away we would use that somewhere to create better soil, and that's how they made better soil in parts of Africa and the Amazon is partly using whatever waste scraps they had, whether they came from the kitchen or from an animal or from us.

Robyn Williams: You have a wonderful recipe in your book for making good compost. There are various ways of doing it, but the wonderful thing about your book, it not only summarises some of the things you've been talking about, but there are nice handy sections where you give recipes for what soil is made of, what a good compost bin should contain, how to avoid ploughing.

But you also do nice thought experiments. And the thought experiment I would like you to do here, being concerned about methane coming from all the different ruminants, the cows and suchlike that we have all around the world, what happens if overnight we removed, got rid of, all of those cows? What would happen to methane and carbon and climate change?

Matthew Evans: You would probably have an immediate global cooling because you would remove that methane source from the atmosphere. But methane has a shelf life of about 8 to 10 years, compared to carbon dioxide is thousands of years essentially. So give it 10, 12, 15 years you are going to be back to where you were.

But the thing that a ruminant does which I think we should never underestimate is when it is eating grass and breathing out carbon, the carbon that it is releasing was the carbon in the grass which was also possibly carbon in soil which was also carbon in air and it's in a cycle. It's not new carbon being added to the system.

Ruminants have been around for 20 million years or so, they out-competed other grazing animals. And so if they are just eating grass they are just moving carbon from place to place, and cellulose, which is what grass is pretty much made of, is indigestible to us but it's digestible by ruminants because of their complex digestion, and it's the most abundant carbohydrate on Earth. So, half the sugars on Earth, which is energy in digestible form, it's not digestible to us but it is digestible to those animals. So if we got rid of them all, we would also be losing a food source.

So the methane climate change argument is very complicated, but I think when you simplify things and say we should just all get rid of the ruminants, you can misplace the emphasis on where the carbon has come from, where it's going to and how do you actually feed the world. And let's face it, there's pretty much no ecosystem on Earth that doesn't have animals in it, and we've removed enormous numbers of animals from the system through the way we've broken up land, and we don't have nutrient cycling. Some estimates are that we've lost 92% of the nutrient cycling that animals used to provide over the last 10,000, 12,000 years. And using grazing animals might allow us to continue that nutrient cycling in the right farming system. So there is no simple system for soil, but soil loves having animals in or near it and pretty much no soil has no animals for very long before it starts to die.

Robyn Williams: Indeed. In a minute I'm going to ask you about feeding the world. If we've got 8 billion, 9 billion, 10 billion, feeding all those with the amount of soil we've got being depleted, as you describe in your book so graphically. But while you're talking about animals, tell me about the elephants and Allan Savory.

Matthew Evans: So Allan Savory is an interesting bloke, he was trying to look after some reserves in Africa and they wanted to preserve these areas as I guess parks or national parks, and he discovered that there was a bit of pressure on the land, he fenced off the land to stop humans getting in there and damaging the land, and discovered that the elephants were over-grazing essentially and were turning what used to be good land into desert. The elephants were just running amok, constantly going around eating all the plants. So he authorised a lot of other people to kill a lot of elephants, thousands and thousands and thousands of elephants.

And then he discovered that the erosion, the degradation of land continued and it made him wonder, did the elephants serve a purpose. And so he worked with other people's ideas on systems where wild animals like elephants before we would confine them and stop the moving around they would move from place to place. So they wouldn't over-graze, they would graze and then move on and then graze somewhere else, and they wouldn't come back to the original place they grazed for a long, long time. And in that period, all of those plants would regrow.

And so his theory is if we move animals around, and that could be domesticated animals, like sheep and goats and cows, which is mostly what we use in farming systems these days, but mimicking I guess wild herds of elephants, big numbers in a confined space for a short period of time, because the animals would bunch together to avoid predators, so they would really trample, poo a lot in one place, eat a lot in one place, but very, very quickly move on, if we can mimic that, can we improve landscapes. And he reckons we can. A lot of farmers around the world reckon we can, and the science seems to be going in the direction that is saying well-managed animals, managed in a system that allows plants to recover, actually store carbon really well in soil and improve ecosystems generally.

Robyn Williams: A good friend of mine who is a weather scientist, actually is at the University of Tasmania, has suggested you could well have elephants in Tasmania who would do you a great benefit. What do you think of that?

Matthew Evans: Well, bring it on. I'm not sure about elephants in Tasmania. This is the thing, I think partly…every time we introduce an animal, and Australia is a prime example of that, you've got to be careful about what the actual repercussions are. And Aboriginal people had 60,000+ years of managing ecosystems and working out a way to do it that they'd be able to feed themselves next year. I'm sure they had mistakes at the start, and I'm sure they had to experiment, and that's what we are in the process of doing now. The difference now is we have to do it very quickly and we have to find the good ways of doing things because we are running out of topsoil and we are running out of time.

Robyn Williams: Which is why feeding the world is a great challenge, I gather one of the main reasons you wrote your book.

Matthew Evans: Yes, it worries me. Some of the estimates are we've lost 40% of our agricultural land over the last 50 years or so. Particularly farming has moved on, if we've ruined a piece of land we just move onto another piece, but we can't move any further, we are running out of land, and we are also increasing our population drastically.

The good news is if we look further afield than simple fixes and yield, if we look at soil as the focus, we already grow enough food to feed 11 billion people or so, but we waste a lot of that, so we can do better in that sense. But we can actually (using techniques that have been developed all around the world but a lot of them perfected in Australia) improve soil, we can grow more per acre and be able to do it into the future.

When the globe is losing a soccer-pitch worth of soil every five seconds and we've got an increasing population, we know we have to turn things around very fast. We have the knowledge, and we have the technology, we have the wisdom, but do we have the foresight and the political will to focus on soil, because soil is what feeds us, 98% of our calories that humans eat come from the fact we've got soil. So if you are not focused on soil and you're just focused on yield, you are not only doing yourself out of a job as a grower or doing your descendants out of a job but you may even be starving future generations, which is a terrifying thought. But the great hope is that we already know how to build topsoil, we already know how to store carbon, we already know how to get good yields, at the same time not depleting this very resource and actually restoring the resource that pretty much grows all our calories.

Robyn Williams: A tremendously inspired Matthew Evans on his farm in southern Tasmania. His book is called Soil.