transcribed and edited by Jack Kittredge and Didi Pershouse, from a talk on May 12, 2018
How did nature create Earth’s biologial system? To find out, we just go back into nature and look at all of the evidence, which is very clear. And the answer is all about pedogenesis, which means soil formation.
The Earth is basically made of “stardust.” Four and a half billion years ago, you had a supernova exploding. That dust condensed down, drawn by its own gravity, and formed into rock: our planet, with 96 natural elements that we can see on the periodic table. About 3.8 billion years ago, the first living cell arrived, probably activated by chemical and heat energy. Then 3.5 billion years ago, we think, that photosynthesis evolved. It came to life in organisms in the oceans at first, but was limited by the meager availability of nutrients dissolved in water and the more diffuse sunlight reaching life there.
Four hundred and twenty million years ago there was still no life on land, and no soil. We had oceans, and we had rock. Dry, arid, hard rock, (slowly degrading by the weathering process of wind and water, which takes 1000 years to form an inch of loose particles.) There was complex multi-cellular life in the oceans, but that life depended on nutrients leaching from the rock into the oceans. And that was the limiting factor for ocean life. Life is pretty competitive, and pretty aggressive, so straight away life said “Hey, if I can get onto that rock to solubilize nutrients, I’ll have a competitive advantage.”
So fungi, which are good at dissolving things, grew tubes of cytoplasm that reached up onto the rock from estuarine edges to solubilize nutrients. But they couldn’t really go very far, because, like us, they can’t fix their own sugars, they can’t make their own energy (only plants and algae can do that and some bacteria.) Basically the fungi needed to form a relationship, a symbiosis with something that could give them sugars to feed them while they went exploring. Of course in the ocean there were plenty of blue green algae. So these fungi and these algae got together, made a deal, and basically said “let’s form a lichen.”
(We can still see those lichens all over this planet dissolving rocks, dissolving our concrete, our wood, our cars, you name it, lichens are eating it up, biodegrading it, having lunch.)
As those lichens grew and moved across rocks, they solubilized the top layer of the rocks, and also left behind their dead cell walls. That organic detritus could hold water, so now we had the beginnings of a soil carbon sponge–mineral particles held together in a matrix with organic matter–and that made all the difference.
Because of that new spongy structure, which continued to deepen, plant life could evolve very rapidly from lichens to mosses to ferns to cycads to gymnosperms to angiosperms and–about 50 million years ago–grasses. Parallel with that plant evolution of course we had the herbivores, the insects, and everything that was feeding on those bio systems. And all of those contribute to soil formation–until you have soils that are meters deep in the prairies. Very rapidly that process of pedogenesis enabled life to extend right across the 13 billion hectares of ice-free land on this planet, and within a hundred million years we had lush deep forests, and deep organic soils, teeming with life.
Whenever we have bare mineral particles, life tries to start that whole process again, and she will, if we let her.
So we started off with just the planet earth as a rock, and just by adding life, and its leftover organic matter, that allowed all of life on land to evolve– and in the process life created deep functional soils. How is that possible? Let’s look at what happens to the structure and function of mineral particles when life adds organic matter to it.
Without organic matter, mineral particles are packed closely together, very dense, with little or no space in between. Now life comes along, actively breaks the rock down, feeds the soil biology, and leaves organic detritus in there, and we can think of that detritus as little bedsprings between the mineral particles: they act as cements and glues, so it gives them structural integrity, but it also creates a sponge, because as those bedsprings push the particles apart, suddenly there are spaces, in the soil, full of air, and the soil grows upwards as it expands. (We know that from archeology because you have to dig down to enter the past.)
By making this change, nature has had a profound effect on that soil. By adding nothing, it has created this matrix of surfaces and voids. It is a bit like a cathedral. By having lots of bricks, and the cements or glues that can hold them together, we can make a cathedral. Now, you don’t go to a cathedral to look at the bricks, you go there to get in awe about the spaces, the voids, the nothing.
More Water Holding Capacity
This is profound. If 60% of healthy soil is voids, that soil can hold enormous amounts of water. And when it holds more water, it can extend the longevity of green growth because you have created an in-soil reservoir. Rock has a bulk density of 2.6 to 3.5 grams per cc, but a healthy soil has a density closer to 1.2 grams per cc: the same amount of minerals, but much lighter and more porous, and all those pores can fill with water when it rains.
More Nutrient Availability
We have also changed the nutrition or the fertility of that soil. Remember, the mineral portion of soil is made up of stardust: 96 natural elements. But those minerals are effectively unavailable while they are in this compact, concrete form. Things can’t get to them. As the soil expands, with more spaces in between, these surfaces open up.
As these surfaces open up, all the nutrients become available on the surfaces. So now we have vastly increased the availability of existing nutrients. even though we haven’t changed the total nutrients at all. Eighty percent of the fertility of your soil isn’t about how many nutrients you have in it, nor about the fertilizers you add to it. It is about the availability of the nutrients you already have there. By increasing the voids in your soil, you are actually making it more fertile!
We are increasing the cation exchange capacity (CEC) of our soil, which means it can hold more of the nutrients that are held by electrostatic charges to your soil surfaces. Think of your soil as Velcro. As you increase the surface area you create more hooks to hang the nutrients on. You are retaining them in a safe way so they don’t leach out of the soil, but in a way the plants and fungi can take them off the hooks and use them.
More Space for Roots to Grow
So by creating voids in your soil you have increased its ability to hold water and to deliver nutrients to your plants. Also, you have massively increased the rootability of that soil – the capacity for roots to proliferate and grow successfully there. We have seen soils that are so compacted that roots can only grow a few inches down in them, but we have also seen prairie soils where roots can grow 10 or 15 meters deep. So now, instead of 15 centimeters of rootability, you have 15 meters – 100 fold as much. When you think of how much additional soil moisture and minerals your plant can reach, it is exponential. The productivity of the prairies grew exponentially like that for 9,000 years, since the last ice age, until we started to undo that with human management.
More Microbial Activity
By increasing the voids and the surfaces in your soil, you also massively increase the microbial activity in your soil. Microbes are living on all those surfaces, on all those roots, feeding off of all those root exudates that are available because your soil has been opened up and there are far more roots growing in it. In a healthy soil, the whole zoo of fungi, bacteria, actinomycetes, protozoa, nematodes, collembola, the whole network of organisms living below the ground is ten times the total mass of life that there is above the ground. If you think there is a cow in that pasture, look below because there are ten more there!
All that life in the soil is turning over nutrients and driving the biosystem there.
It is these four things that govern the productivity and resilience of our landscapes:
• the water stored in the soil
• the availability of the nutrients there
• the amount of roots growing through it
• and the presence of microbial life.
They enable the landscape to buffer climate extremes such as flooding, drought, heat, and winds. You don’t need a lot of carbon in the soil. Two to three per cent is enough. It is not the carbon that counts, but the cathedral that the carbon builds – that matrix, the surface area, those voids that are created.
Let’s talk about health.
The crucial thing about life, which goes back to the first cell some 3.8 billion years ago, is the concept of a membrane, which is the most basic form of intelligence. The first cell had an oily, filmy membrane around it, that distinguished the cell from its surroundings. We talked about stardust, the 96 natural elements that make up stardust. We’re just made up of solar energy and stardust. Every living thing on earth is made up of those, and we need most of those elements (nutrients) for our biochemistry. Scientists don’t know exactly how many nutrients we need (they add more every few years) but let’s say 50 plus is about right. We also know that there is a whole group of elements that are toxic to life.
So, back to the first cell: what was unique was the capacity of this membrane to concentrate essential nutrients. There might have been 20 parts per million (ppm) phosphorus out there, but life wanted 200 ppm inside. These cell membranes had the ability to take that phosphorus in from the primordial soup and concentrate it inside the cell. At the same time, these membranes could exclude toxic nutrients from coming into the cell. If we had 200 ppm of aluminum, cadmium, or mercury in the external environment, and only needed 20 ppm, they could do that as well. A critical aspect of life is such an ability to distinguish itself from the environment and create an internal environment conducive to its own biochemistry.
Our health is totally dependent on this biochemistry of our internal cells, which is possible because of these intelligent membranes that can concentrate or exclude elements.
Some nutrients are only needed in parts per billion, and would be toxic in higher amount, but are still vital to have. For example selenium is essential to life. If we don’t have enough, we can’t make peroxidase enzymes, and without those enzymes, we can’t kill cancer cells in our bodies. But in excess, selenium is toxic for us.
So it is these selective interface mechanisms that govern life.
All through the evolution of life there have been two key processes through which plants have taken up nutrients. In nature 98% of plants depend on mycorrhizal hyphae – which interface with plant roots and proliferate throughout the soil – to create a whole matrix of those sort of selective membrane interfaces. These hyphae, interfacing with the soil, are involved in the selective uptake of essential nutrients and the exclusion of toxic elements. That selective interface is a quality control system between the toxic environment and the living cytoplasm of the cells.
This hyphal interface, in a natural soil and plant biosystem is absolutely extensive. There are up to 25,000 kilometers of fungal hyphae per cubic meter of healthy soil. That is over 15,000 miles–almost twice the diameter of the Earth!! Not all soils have this. That only happens in a healthy soil.
Where you have a zinc deficient soil the mycorrhizae will be concentrating the level of zinc to give themselves–and thus the plants they are relating to–an optimum level of zinc. But if you have the same mycorrhizae and plants in a high zinc soil, they will be taking up enough but preventing any more being taken in. They are intelligently regulating those 50 plus nutrients to get the optimum amounts they need
Plants colonizing toxic soil require mycorrhizae because they have that intelligent exclusion capacity. Plants without that mycorrhizal interface will not survive the toxins. CSIRO (Commonwealth Scientific and Industrial Research Organization: an independent Australian federal government agency responsible for scientific research) did the work in the 1970s to show this. In these circumstances, natural selection will select for particular mycorrhizal fungi which can exclude those particular toxic substances. The ones which cannot do this do not survive contact with the toxins.
So nature has depended on this soil/microbial/root interface for the last 420 million years to grow plants on this planet. It is that interface that we have depended upon, up until World War II for the nutritional integrity of all our food.
But if we go post World War II, we get into a totally different form of nutrient uptake. In industrial agriculture, instead of depending on these mycorrhizal hyphae as the basis of agriculture, we have used massive amounts of clearing, burning, over-fertilization, and biocide treatment (including the whole range of insecticides, fungicides, herbicides, and of course bare fallow – which is like growing plants in a concentration camp). All of these things absolutely wipe out this mycorrhizal interface. If you cultivate, ultraviolet radiation will also kill these fungi. Excess fertilizers will kill them. Biocides will interfere with them, and bare fallow will starve them because there are no plants to give them sugar via root exudates.
We can call this new system “industrial hydroponics” even though we are talking about plants growing in soil. In an industrial system the soil has lost its health and these mycorrhizal interfaces are lost so we have a completely different nutrient uptake situation. We still have mineral particles, but the carbon is largely oxidized. And these mineral particles still hold our calcium and zinc and selenium by their cation exchange capacity on their Velcro hooks. But there is no longer anything to concentrate them, or regulate the quantity needed. The plant is in a totally new environment because all it can do is take up nutrients passively from the soil solution. That’s why I say this is essentially the same as hydroponics. The plant can only operate as we would if we were drinking water with a straw. It takes them up as part of a transpiration stream without any quality control whatsoever. Whatever is in the primordial soil soup goes into that plant. Plants are operating blindly, without an intelligent selective interface.
The roots are there and perform a certain function, but not in selective, intelligent uptake. The hyphae take up things through a semi-permeable membrane, actively whereas the roots are just doing so passively. When roots take up nutrients they don’t go into the cytoplasm of each cell, but just go directly into the xylem vessels in the roots as a transpiration stream.
So the soil solution doesn’t get taken up across the cytoplasmic membrane from one cell to the next to the next. There is simply a straw that is taking up volumes of water without that biochemical interface. The nutrients are still available on the CEC surfaces, but there is nothing to take them off.
Now, instead of the proper balance and ratio of nutrients, we have whatever is in the soil solution. We have our nitrates, our sulfates, our sodium, chlorine, aluminum, lead, cadmium, etc. We get all these anions and cations that don’t exist so much on the cation exchange level but are in the soil solution.
If you have toxins or manmade biocides in your soil solution, like glyphosate, then you have totally new, unnatural molecules from their breakdown products in your soil solution. In the absence of the living mycorrhizal interface these can also get taken up and absorbed by the plant. These molecules then can transfer to the animals that eat the plants and cause changes to the microbiome in those animals.
In the Chesapeake Bay you have breakdown products of toxins and genetically engineered plants and all of a sudden the shellfish are getting cancers and growth deformities from trying to filter feed biomolecules that they are just not able to handle.
Nature has evolved for 3.8 billion years breaking down chemicals and we have evolved the biochemical capacity to live off those breakdown products. The microbiome that exists in the soil, we have something like that in our own guts. It too operates as a breakdown system and a selective intelligent interface between our gut and the foods we take into our body or the ones we reject and expel. It is really a second layer of quality control which we can disturb by taking antibiotics and drugs and what have you.
We grossly disturb that biochemistry when we add novel biomolecules there that our whole system has never adapted to. We quite frankly don’t know what the consequences of these novel compounds are. They have never been identified, never been tested. It is a big question mark, and we are seeing major consequences in organisms in our environment and humans as well.
Of course we had some of these toxins and biocides before World War II, but after the war there was a massive increase in the use of agricultural chemicals, fossil fuel use for power instead of draft animals, plastics and petrochemicals.
It was only after World War II that we had the horsepower, and the whole massive mechanization of farming at that scale. We had tractors before, and soil degradation, but nothing at this sort of global scale. It was at World War II that we had the energy, the fossil fuels to put into agriculture, we had the equipment from that whole industrial effort, we had the fertilizers from the munitions industry and of course the nerve agents that we turned into biocides.
We now have 270% of the natural nitrogen fixation of this planet that we are annually putting onto our soils because of the Haber-Bosch process of making nitrogen fertilizer from natural gas. We all need nitrogen to sustain life, but do we need it at such a level? It’s a bit like heroin, isn’t it? Lead, cadmium, other elements we don’t need for life but our industrial system has unleashed and much of it is now in our soil – leaded gas is a perfect example.
We have killed that intelligent selective quality control system both in our soils and increasingly in our own microbiomes.
This is quite fundamental because it makes the point: what is the difference between food grown in these natural microbial based processes compared to the “industrial hydroponics” that most large scale food production is now driven by? The nutritional integrity of the food grown in the first process is fundamentally different from that of the food grown under industrial agriculture.
What matters is not how many milligrams of nitrogen or sulfur are in the soil and can we measure that, but can we have confidence in how our food was grown. Do we know that our food was grown in this natural way, relying on these processes that our great, great grandmothers counted on – the fungal selection and intelligent uptake. When it is grown industrially in this hydroponic-like soil solution, we get none of the essential micronutrients we need because they are locked up on soil surfaces and can only be made available by these mycorrhizal processes. That whole story of the sponge, nutritional integrity, the quality of our food, and our health is of profound significance.
If we degrade these natural microbial ecologies we are compromising the integrity of that food. Food now, according to the USDA, the CSIRO in Australia, and the UK Ministry of Health contains less than a third of the nutrients per gram of food it did pre World War II. You have to eat about three times the bulk of food you did before to get the same nutrition. Your body gives you subliminal signals and we end up eating, eating, eating, and get plenty of starch, salt and fat, but not the nutrition we need.
If we want to be sure how our food was grown, we need to know what level of localization is needed in our food production to give us that assurance. If you are importing stuff from China, for example, how would you know?
This is pretty important because it relates directly to our food. According to Linus Pauling 90% of our health is directly related to what we put into our faces: our food. We have created this pandemic of self-induced food and diet-related diseases. It is growing exponentially and driving a $4 trillion disease industry in the United States, growing at 6 to 9 percent, depending on what category you are in. That is totally unsustainable over the next ten years. We just won’t have enough health insurance money to pay for it. But you won’t be here, so don’t worry about it!
We need to get this message to every parent and grandparent that yes, the quality of the food we eat matters, and here are the criteria by which we can assure that nutritional integrity. Not reading a package like an encyclopedia to see how many milligrams of what are in it, but: has this food been grown naturally? Of course we can do nutritional analyses on representative samples, and we have bioassays that can tell us if these soils have mycorrhizal activities that can give us that assurance.
There is 270% of natural nitrogen now being used in agriculture. Nature used to fix 100% of its needs through rhizobia, actinomyces, blue green algae, and other microbial nitrogen fixation. We are adding another 170% of that natural level as fertilizer.
All nature’s processes are critically important. Nature doesn’t have winners. These processes are all part of the jungle. Nitrogen fixation is just as important as phosphorus uptake, as selenium solubilization, as toxic exclusion because if any of these processes are failing or not optimal it can limit life. Nature runs at optimum. Most vegetation needs 20 to 30 kilograms of nitrogen per hectare per annum to be at that sweet spot. Nature can readily provide that through microbial fixation. The fact that we are adding, in some countries, 200 kilograms of nitrogen, not 20 or 30, means that we are running at this toxic level.
The roots of plants don’t select nutrients in the same way mycorrhizae do because the roots are taking up nutrients in their water stream. Also, the surface area of root hairs compared to membrane interfaces is like one in a million. They just don’t have that capacity to interface and selectively take up what they want.
Brassicas don’t relate to mycorrhizal fungi directly. They put out a lot of sulfur compounds and organic acids that are then involved in solubilizing nutrients directly. They are very important pioneer plants colonizing primary soils. They actually inhibit fungi, not by killing them but by sort of fungistasis, just putting them into hibernation.
If you have a brassica field that is a monoculture, after several years it will put the mycorrhizal fungi there into hibernation. Some will survive, but they might be operating at 1% or less of their natural activity. Of course the sweet spot, as in nature, would not be a monoculture but brassicas in microsites solubilizing and having grasses and other plants growing with it. But if you have a bare moonscape where you just need plants, Brassica have an important pioneer role to play.
Of course there are no ‘bad’ plants in nature. We just have to read her and learn how to move forward using what she gives us.
Walter Jehne is a retired scientist with a specialist background in soil microbiology and plant ecology who has worked in Australia and overseas, including for CSIRO. He is now part of two not-for-profit groups, Soils for Life and Future Directions International, which foster solutions for the regeneration of Australia’s landscape and the development of the agricultural and pastoral sectors of Australia
To watch a Walter Jehne talk at Harvard on Water Cycles and the Soil Carbon Sponge, go to https://bio4climate.org/blog/walter-jehne-april-26-2018/