Transcript

In the beginning there was rock. In the early evolution of the Earth there were lots of rock which had no life. It was just grounded rock from tectonic activity from volcanoes. All this with volcanoes especially would spew out lots of rock into the neighbouring ocean. This rock would lie there until it was eroded by the wind or the sea or chemical erosion. So, this erosion was basically the grinding down these rock particles into smaller and smaller sizes.

it's just all about grinding it up and this was sort of the early primitive soils and this was hundreds of millions of years ago and in order to make soil. Here the key ingredients, so you need this grounded mineral rock or minerals which contain a lot of nutrients such as phosphorus, and potassium. That's why you typically see lots of beautiful farmlands right next to volcanoes because of the ash, which contains. So many nutrients for the plants you need organic matter, life, water and gases. After a thousand years of going from this rock you can then go on to arable farmland soil, which is down here at the bottom.

It takes about a thousand years to make about three centimetres of arable farmland so it's a very slow process. Continuing on the theme of going back in time - going back about 420 to 430 million years ago you would have this soil; you have this rock erosion occurring and this is when the early life forms early plant life was forming. I’m just going to summarise a few hundred million years of plant evolution for your convenience. If you imagine this was barren rock next to the sea. The ancient ancestors of plants were fungi like algae-like living cells and they were in the ocean for billions of years pumping out oxygen as a waste material, and one of the major advantages of being in the ocean is that you can easily take out nutrients from the ocean, which is flying around all around you.

That's what was happening in the ocean. We can take out these nutrients and over a spare of a few hundred million years these little algae beings would then land onto the rock neighbouring rock slap onto the sea. They would then start to deal with the pressures of being outside in the open atmosphere, and quickly moving on to this we have the earliest known land-based plants which is the Cooksonia. They were about one centimetre high and they were very primitive plants; they didn't have a vascular system; they didn't really have they didn't have roots, no flowers, no seeds; they were just little green sticks.

They moved onto the land, and it was basically a competition pressure because in the sea we have lots of competition, lots of these algal beings. They went onto the land and they grew there but they also faced a lot of pressure, and a lot of stress because in the ocean you have nutrient availability all around you. Whereas, on the land you have to get it from the rock, and the rocks when particularly easily habitable they didn't have any early soils that plants could grow in.

These early formations, these early land plants were believed to form fungi associations to help them establish themselves on the land so this is represented by the orange squiggly line. And fungi were on the land before plants it's believed and this association helps plants to take a stick in the land. They proliferated into what we now know as rainforest etc. And the gradual introduction of these plants on the rock, they would live die live die and this would introduce organic matter into these grounded rock. So, this is just helping the early formation of soils.

This is a similar process that is happening today, which we can look back and use for early soil investigation is a glacial rock. Here we're in New Zealand you can see there's a glacier and as it's moving down or closer towards the mountains. You can actually see ground-up rock being left in its place and this ground-up rock is an early form of soil - just as it was a few hundred million years ago. You can see grounded brock has been left at the bottom of this glacier and early plants should I say such as moss are moving in to colonise the soil and generations of these mosses and very small plants would live die live die in the soil introducing organic matter into it as it rots.

As the roots break up the soil in the ground up rock is basically making soil. After a few hundred million years of this grounding of introduction to organic matter you get the lovely farming fields. The rainforests are of little soil so, this is how soil actually formed. Soil is formed of this mineral component as well as lots and lots and lots of organic matter and carbon dioxide being pumped in.

Now we know what soil is and how it formed. Why is it important and why should we care? Soil is the basis of all ecosystems on the land on Earth - so at the top right we have a picture of a rainforest without soil trees plants would struggle to grow, and soil is bare is very important for all land-based crops, which inevitably feed animals. Most of your crops and animals actually depend on soil without them. We would struggle greatly without it. Soil is also the second biggest carbon store on Earth, second to the ocean so in order to fight climate change it's very crucial. We also get surprisingly a lot of medicines from the soil so there's a lot of fungi, bacteria - full of life in the soil so you might have heard this old saying of ‘one teaspoon full of soil contains billions of life forms’, and that's true. There are so many single cell organisms in soil and it is full of many discoveries including a lot of antibiotics.

So, soil is a big biodiversity store, carbon store and it provides so much of our systems needed for life. I mean if we go back to the early slides where it was barren rock, what would you prefer? Barren rock or rain forests? This is where I’m going to briefly touch on my research at Leeds University. So, I specialise - like Becca said in the plant root soil interaction. Many people know that plant roots take water and nutrients from the soil but that's about it but that is actually very simplistic and to a degree quite untrue. They also do lots of other things so as well as taking water and nutrients from the soil, they actually secrete this mucilage, which is formed of very complex polysaccharides that are small chains or sugars popped together into long chains. This sticky mucilage has many functions, it helps to lubricate the root caps and tips through the soil.

Mucilage also helps reduce friction as they go deeper and deeper into the soil, and this mucilage is also known to help regulate this plant root soil interaction, which is known as the rhizosheath. ‘Rhizo’ being the root and ‘sheath’ being the interaction point. This polysaccharide helps in some plants it's been shown especially grasses they can actually secrete more during periods of drought to hold onto the soil, to take more and more nutrients. When the conditions are right, they don't secrete so much but the mechanisms of regulation are completely unknown at the moment and as well as this mutual secretion uptake of nutrients and water plants also release whatever's in the cell of the root so this is known as the exudate. So, plants release DNA, release all sorts of proteins whether this is regulated or not it's unsure, and this mucilage contains lots of biomarkers that other insects’ plants use.

Some plant roots will compete with each other, and will have overlapping rhizosheath areas over the top here, and of course, parasitic worms, bacteria fungi also want to interact with the roots. They detect these biomarkers and of course, a lot of gardeners know these days that arbuscular mycorrhizae fungi which is a beneficial partnership with plants that they also seek out. The fungi also seek out the interaction with plants via this exudates and possibly mucilage. This interaction helps plants secure more water and nutrients from the soil, and in exchange they give carbon in the form of sugar to these fungi, which helps them to live.

This is a very brief sort of summary with lots of words, and whatever but it's to show that plant roots don't just take from the soil we actually give a lot. This is a rhizosheath image in real life so this was a wheat crop that was pulled from soils and dried so we could actually take it out. And as you can see if you can see the cursor but going along the roots there's a long root here and it actually holds onto the soil. this is what the diagram was showing so this is in real life. This is the point of which roots take water and nutrients out of the soil. If we use a more sensitive microscope, we can actually see the rhizosheath in more detail.

To the left this is just a standard image of a root with soil so you can see the roots sort of coming down the slide, and curve any black blobs that's purely organic matter, and anything that's partially see-through like at the top is actually minerals in the soil. Then to the right of this image, this is an antibody stain so this is very specific to one of the major components of this mucilage, one of the polysaccharides. This is in green so again we have the root that's bending down and you can actually see quite a lot of mucilage has been detected in this rhizosheath. You've got a bit of organic matter to the top of this black blob which has a lot of green emanating from it, and you can actually see some of the roots bending and twisting on these black blobs. You can even see them bending on this see-through mineral here to the left. Left centre of the image you can see that this mucilage is almost wrapped around this particle and this is what's happening in the rhizosheath.

As my research looked into these polysaccharides, this is what I’ll be focusing on for the rest of my talk. You can see these polysaccharides as well as the roots are holding on to the soil so that the plants can take water and nutrients from soil. So, we know what soil is, we know why it's important, but what is soil erosion. Soil erosion, like we've discussed with the rock it's the grinding down of soil particles. To the bottom left here we have lovely organic soil which is full of organic matter - large particles and small particles - is varied. But soil erosion is when this soil is exposed, and is subject to drought or flooding and anything drives these particles to break up. Erosions where it breaks down aggregates - the clumps of these particles break down into smaller particles and then into smaller particles until eventually the soil becomes exhausted.

All these particles are quite similar in size and it's completely broken down so you can't grow anything on it. This is also known as desertification, where the soil completely breaks down and this is bad because we don't want to lose soil in the fight against climate change, and of course we depend on it for our food.

So, what are the major causes of soil erosion? Unfortunately, a large part of it is human activity; to the top left farming practises at the moment do have quite a big impact on soil erosion. At the moment the standard sort of procedure to grow crops is to grow them on mass scale - on monocultures so this is picking one variety of wheat growing in a large field. Ploughing the field, harvesting, ploughing in the unwanted stems material, tilling it and this puts great stress on the soil. In the natural sort of world, you have trees next to plants and shrubs and different types of species. It's very diverse, very diverse root types but in these monocultures there's one type of root, one type of wheat variety, big monocultures. So, its low genetic diversity is affected in soils and of course, deforestation reduces the soil’s ability to hold on to itself.

If you pull out a tree, this kills off the roots and there's nothing to hold the soil in place whether by the actual roots wrapping onto the soil or this mucilage. Against other factors as well, the use of chemicals it's more specifically fertilisers such as nitrogen, phosphorus and potassium. Farmers put this on the field, obviously to bolster growth but it also reduces the plant's reliance on these fungi interactions and when plants have enough nutrients they don't want to interact with fungi. If they're currently in a partnership with fungi they will get rid of them because they don't need them. Whereas, plants that desperately need nutrients – they really do seek out these interactions.

So, the chemical fertilisers and the big monocultures aren't particularly helping the situation and of course tilling this is after harvesting your crop, you put the secondary ‘waste’ products that you don't really want back into the soil. You dig up the soil like in gardening at home you put the weeds etc. back in so you're constantly breaking these soil particles down. The plants haven't really had a chance to hold on to that. And of course, the final sort of issues are extreme weather via climate change, which is really speeding things up for us through droughts where soil breaks down and blows away and of course, floods where it washes away. And at the moment we're losing about a hundred thousand kilometres squared of arable farmland each year which is equivalent to South Korea. So, every year we're losing the equivalent of that, which is quite shocking.

This is where part of my research was coming, exploring how to reduce the likelihood of soil erosion and examining soil health. We have two different techniques one to the left is wet sieving and this is standard in geographers’ terms/soil scientists. This is where you add your soil sample to the top, where you have a series of descending sizes. At the top you have the largest, about one millimetre squared all the way down to 90 microns, which is very small. You put the soil in, you place the sample down with all the sieves, and you then subject it to a torrent of water. These sieves are shaking violently and this examines these aggregates of these particles stuck together to see if they are water stable and of course the more stable they are, the healthier the soil or at least there's an indication of a good health of a soil.

To the right, this is a fairly new technique that I helped to develop and it's known as Dry Particle Dispersion Analysis, this is typically used in chemistry and particle science that we apply the principles anyway to dry soil samples. In this technique you have your soil sample you then put into a blast chamber, which you could probably see just to the left of that image. Then this black shape comes along to the glass slide and sticks on and the soil sample is subjected to a liquid nitrogen sneeze. This is quite impactful for these little particles and the theory is if the aggregates are strongly associated with each other as they hit the slide, they will remain together if they are weakly associated, they will hit the slide break apart. This causes a bit of a mess but this is another indication of the stability of these aggregates but from a more mechanical point of view.

In theory if the soil is very healthy, these aggregates will remain together no matter the torrent or the liquid nitrogen. So, this is actual research that's been published for a while. This is the soil sample, to the left the ‘na’ is the no additional control - this is just purely soil that's been sterilised. There are no life forms in, and then to the right ‘XG’ this is a commercial form of polysaccharide that is secreted by these plants so this is xyloglucan. This is the commercial equivalent component as to. Say and we added this into the soil at a typical concentration that is typically found in this rhizosheath. If you go back to that image with the green staining, that's what we were detecting.

This is the commercial form because it's easier to use and it's more available. As you can see the blue bars are anything above one millimetre cubed so, this is a fairly large particle, a fairly large aggregate of soil. You can see the distribution of soil aggregates going up this chart here but when you have this xyloglucan or ‘XG’ the blue bar, which is the aggregates above one millimetre cubed is greatly enhanced. This result shows that adding this xyloglucan or commercial equivalent of xyloglucan stabilises the soil and is water stable, so this is a good indication that it's helping to increase the health of soils.

Now when we subject our samples to another test, to actually confirm that these aggregates are stable this is dry particle dispersion analysis. In red we have no additional control again this is just soil that's been sterilised but when you add this side of glucan you can actually see any of these aggregates, above one millimetre cube, the fairly large is greatly enhanced. This confirms that adding this commercial form stabilises the soil and actually increases its health. The health of the soil at least one indication is that these aggregates are held together and not blowing away.

Just to visualise what is happening in these results we use scanning electron microscopy. This is useful in getting a detailed image of these particles. As you can see to the left the ‘na’, no additional control - so this is just purely soil - you can see the whole distribution of particles in the sample. If we pick one, here to the bottom it's quite smooth in appearance and you can see there's a little bit of sticking to smaller aggregates and particles but there's not really a lot going on here. But when you add the xyloglucan, you can see there's a lot of rougher looking particles, here but when we zoom in we can actually see this clumping effect - this aggregation. You can see there's one particle here, little bits here so it's almost like an asteroid in appearance, clumping on and this is a good indication of soil health. So, this is visualising the importance as I would look at binding soil together.

So now we know it's importance of soil, we know it's eroding because of human activities but how can we protect it? There are four key approaches that we could use all of which need quite a lot more research to apply to an industrial scale. So of course, one of the easiest options for us is to reforest areas. This will then increase soil aggregation via mucilage and introduce other life so when you cut trees and you look after those trees that they grow mature it brings other life to the area. Plant other trees it needs to be specific to a local region; you can't put invasive species in the area. It needs to be local species and it needs to be high diversity, so you can't just put monocultures on trees which doesn't help.

You have this diverse forest mix and of course, when trees get established all the plants get established it brings in more life and more life, more roots, more mucilage, more fungi interaction and there are more things holding onto that soil. More things growing on it, prevents soil erosion and of course, we can reduce our consumption of fertilisers which is already happening because of the cost of fertilisers. At the moment the cost is very high and it's ever increasing. Farmers don't really want to waste money on things so they are naturally reducing their consumption but still, we are applying lots of fertilisers for efficient crop production. Some of this leeches into our rivers and causes mayhem. We can find more sustainable options for reducing fertiliser consumption, we can explore the use of mycorrhizae fungi so when again plants require nutrients that they're not getting they really want this interaction, which helps them. We can explore ideas about increasing partnership with fungi and bacteria.

On a mass scale there is no-till farming, which is becoming more important in the fight of soil erosion. This is where after you harvest the crop you just leave the material on the surface of the soil to prevent it from drying up and eroding but, unfortunately having this on such a mass scale there's a few issues of disease and pests. There's much more research needed into no-till farming, to hold on to these particles. We need to move towards more sustainable practises to reduce meat consumption, and less animals - there's lots of debate around this area. Of course, we can explore these polycultures so this is where you don't grow on mass scales just one species you can actually pick a few varieties for your species. Although on a mass scale this is quite hard to do. But in orchards typically you can grow apples with cherries or apricots for instance. And of course, many gardeners or people who are in allotments do this naturally; they want to grow quite a few different vegetables. If you can find this on a mass scale this may help reduce erosion.

Covering the soil different types of roots holding on different types of secretion and of course, which is a very difficult thing to do. Although it sounds easy to reduce emissions if we do reduce our emissions, which reduces the chances of extreme weather and thus much soil erosion. But of course, that's very difficult. I’m going to move on to some wacky idea but it is an idea that I have explored, believe it or not but with NASA. If we want to colonise different planets, we need to make soil. Of course, we have different growing techniques such as hydroponics, aquaculture, aeroponics and X-plants that are growing in little tubes, but this can't really be done on such a mass scale for planetary colonisation.

On Earth we have beautiful soil but, on the moon, and Mars, or other sort of planets we don't have soil. On these worlds we have something called regolith, this is just ground up rock - essentially on the surface of these wells sort of early soils. But they're not going to be like any soils on Earth. There was a NASA study quite a long time ago that used the rock collected on one of the Apollo Missions to simulate more of this regolith, to see if it could sustain plant life. Believe it or not, within a hydroponic system or even direct growth using this regolith could actually support plant life or crops. Fascinating research was done in the 70s and 80s - it was quite old.

In theory, if we get to the moon, we can actually take this regolith and grow plants with it but we would have to of course, add nutrients to support the sort of growth. In hydroponics essentially you just need a material to hold the plants together so it can certainly be used in that system. Now any SpaceX people out there, if you want to colonise mars and use the regolith there, as in such films. Well unfortunately, you can't use that regolith. The Martian regolith contains perchlorate salts, which are highly toxic. This is quite a dead world essentially. These salts are very toxic to plants and again, there was a NASA study a while ago that looked into these perchlorates and tried to simulate Martian rock. Unfortunately, it could not sustain plants for very long. But of course, in theory this research said that if you could clean these perchlorides out efficiently you could in theory use it to support hydroponics, aeroponics or even direct growth. But a lot more research is needed, and of course samples would be nice.

For any interplanetary person, we need soil to colonise, and I did actually include this in my PhD thesis and my examiner did laugh, but it is true that it could be used. So, coming to the end of this talk. Take home messages; it takes a long time to produce soil, soil is home to a huge biodiversity of living beings’ bacteria, fungi, plants, invertebrates’, worms, moles and so much algae. It's also a huge carbon store and we can use it to pump carbon dioxide in through the natural means of growing trees and reforesting things. And of course, we are starting to explore technology of sucking carbon dioxide out of the atmosphere and company into the soil but this is very early-stage technology. We depend on it for all crops on the land, which subsequently feed cattle and poultry.

Current agricultural practises are eroding this soil at quite an alarming rate of equivalent size of South Korea. But we can protect it. A poor soil that is badly eroded can't be undone. We can protect what we have in such ecosystems as rainforests. And of course, the soil is awesome. Get excited about it, go into your garden, put your hand in it, feel it, see what you can see, what fungi and bacteria you can see. So, the soil is awesome.

I’d just like to have honourable mentions here. I’d like to thank my lab group that was a part of in Leeds, so Professor Knox who led the group and Sue Marcus especially who was the lab manager and all the other postdocs PhD’s and technicians. I’d like to thank my funders which are the BBSRC and the University of Leeds at the time. And I’d like to thank SEB for allowing me to talk to you about one of my passions and yes that is an image of us in the graveyard because that's the type of lab group we were. So, thank you for listening and happy World Soil Day, which is actually on Sunday but I don't do talks on Sunday. Social media bottom website but thank you again for listening and if you've got any questions, I’d love to answer them.