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The way we look at soil shapes the science .....
Soil science encompasses various disciplines such as geology, biology, chemistry, and environmental science to understand the physical, chemical, and biological properties of soil.
Soil scientists investigate the composition and structure of soils, including their mineral content, organic matter, water-holding capacity, and nutrient levels. They also study soil fertility, soil erosion, soil conservation, and the interactions between soil and plants, microbes, but rarely small animals.
The field of soil science is important for understanding and managing agricultural productivity, land use planning, environmental conservation, and remediation of polluted or degraded soils. Soil scientists often work in collaboration with agronomists, geologists, ecologists, and environmental scientists to address various issues related to soil health and sustainability. Now soil science plays a key role in global warming.
Shaler considers 'the moral relations of men to earth is attained by the method of science in a simple way; follow step by step the history of the earth's features and noting the processes by which they have taken form'.
We shall follow Shaler's 'method of science' - over 130 years later - to explore soil evolution. I believe we need a change in the way we see soil, that leads to a 'paradigm' shift in our thinking in soil science
But first, let's see how soil science has already developed.
Soil science is a branch of science that studies the formation, classification, mapping, and fertility of soils.
Soil Science
Soil Science
Over the years, soil science has evolved significantly. Traditionally, it focused on soil physics, about weathering to produce sand silt and clay and how they mixed and moved together. It gained greater prominence in the 1800s when more attention was being paid to fertility, in fact going to war to get bird dung. The chemistry was studied leading to the first ever Agricultural Research Station @ Rothamsted.
Nowadays, it has expanded to include broader environmental concerns, particularly global warming. Soil conservation, land-use planning, and ecosystem health features. Advances in analysis technology, like remote sensing and molecular biology, are producing new ways of seeing soil. We are developing interdisciplinary approaches, where once we were in soil silos, to address complex soil-related challenges.
Early Soil Science
Early Soil Science
Prior to Schaler's work, there were two co-existing theories about soil. You can still hear them today. They were a ‘nutrient-balance’ theory where we just replace every chemical we’ve removed in crops to 'balance' them in the soil. To this day, the UK government uses ‘Nutrient balance’ as a measure of long-term trends. (Nutrient Neutrality). This ‘balance idea’ ran alongside a general belief that soil was made of a mixture of disintegrated rocks, following weathering. Weathering is a crucial process, but does not in itself produce soil, but silt, small particles of various minerals.
Frederick Fallou, around 1860, explained why soil formation was worthy of study and appealed for recognition of soil science as a discipline. He was followed by Vasily Dokuchaev who set the scientific basis of soil science as a natural science. He and Russian colleagues considered the soil as a natural body having its own genesis and its own history of development. This soil has its own complex and multiform processes taking place within it. This was revolutionary, as Russians collectively considered soil a completely integrated natural body. Dokuchaev called it the 'fourth natural body' set up the classification of soils we use today.
The Russian concept was broadened and adapted to conditions in the United States by C F Marbut to emphasise individual soil profiles to the subordination of external soil features and surface geology.
Photo Global Soil Partnership
Darwin
Darwin
The contribution made by Darwin and the importance of earthworms in turning over soils, is well known. Darwin learned - mainly be getting his nieces to do the counting, that worms literally move the earth in the process of their meanderings. Their passage through the earth aerates the soil and the natural chemistry of their guts renders soil and plant matter into fertile pellets. We shall find, as we trace the evolution of soil, just how significant animal poo plays - and that includes millions of tiny creatures not just the great bug worms. Decomposition was not always part of the soil, as we shall see, and consist of both aerobic and anaerobic decomposition.
Shaler, a few years later, went on:
“The magnifying glass shows that the process of decay is fracturing all the fragments of rock along their structural planes, joints, or cleavages and this indicates that some action is at work which serves to break up the stony matter of the soil, where a deposit at a considerable depth below the soil do not exhibit this progressive decay”.
Darwins' worm poo
Pedology has been the main branch of soil science for many years.
Pedology
Pedology
Primarily it examines the 'peds' or lumps of soil and how they are formed through aggregation. It focuses on forming, morphology, and classifying soils as bodies within the natural landscape.
Soils are classified in a similar way to plants and animals, all having stratified classification from Order to 'species' Different systems apply in the world, with a world order followed by Europe and the US version, somewhat simpler. See Classification
All types of soil are formed by factors like climate, parent material, topography, and living organisms, based on similar soil functions.
Holistic
Holistic
In recent years, the way we look at soil is changing. We need to examine soil as a whole.
"To fully account for soil functions, we argue that a holistic approach that centres on the pore space is mandatory while the dismantlement of soils into chunks may still be carried out to study the binding of soil solid components." (Vogel et al., 2021)
The characterisation of fragments requires dismantling the soil, the investigation of the pore space is only possible on undisturbed soil samples.
Peds & Pores
Peds & Pores
Peds
'Peds' ruled the science, but now we have begun to realise that most soil functions go on between the peds - in the pores. Breaking soil up to examine it misses the role of pores. There is a complex continuous dynamic between the solid peds, through the water films and in the air, creating a complex chemical environment for soil to carry out its functions..
Pores :
To look closer into the pore spaces we need the help of a new technology - the microfluidic chips Microfluidics refers to the behaviour, precise control, and manipulation of fluids that are geometrically constrained to a small scale (typically sub-millimeter) at which surface forces dominate volumetric forces. This could help explain some of those characteristics of soils that make it so amazing. It can be bone dry and look and feel very dead after a long drought. But somehow perk up quite quickly with sufficient rainfall. And when we water pots that are very dry, the water runs straight off. Then after a bit more moisture, it doesn’t run off as quick, and then when we come back to water again, they absorb much more water. We see it all the time – but how does this happen?
Pores
Pores
Darwin (Vegetable Mould Vol 37) looked at pores and their importance for water infiltration and as a pathway for the incorporation of organic matter into soil by the action of earthworms. Water properties such as hydraulic conductivity, infiltration capacity and water retention characteristics are indirect methods to address pore scale attributes or functions. They are still widely used today.
Peds
Peds
Zakharov (1927) proposed early in the last century, a classification scheme to characterise soil fragments and aggregates. He used both terms as synonyms – with respect to their size, shape and surface roughness. In principle, this approach is still part of soil mapping protocols in the field today, reflecting different way soils are investigated.
"The term 'structure' is increasingly replaced by the term “architecture”
Architecture
Architecture
We speak about the soil structure as being its unique feature, distinguishing it from sand, silt and clay alone. Soil has a distinctive structure of 'peds' produced by aggregation, and the study of these makes up the main science of soil - pedology. These aggregates are made of minerals, chemicals and debris that is full of life. That living entity has evolved, and so along with it the various structures. These structures respond to all sorts of physical and chemical forces, continually growing and adapting to maintain themselves.
"The term 'structure is increasingly replaced by the term “architecture” to emphasize the close relationship between the arrangement of soil physical constituents in space and the functions that such arrangement enables. Soil architecture is manifested through spatial configuration of pore networks produced by well-known processes of root growth, faunal activity, swell–shrink dynamics, and freezing–thawing cycles, within a soil matrix containing primary pores between particles, variably cemented by organic molecules and physicochemical interactions. "(Vogel et al., 2021)
We have seen in this history of soil sciences that there are 2 main approaches to investigation, one studying the peds the other pores, that are coming together in 'architecture', a discipline well used to dealing with the two together, as that is what buildings do.
We can start to think that there may be all sorts of 'buildings' in them thar peds and aggregates. The soil structures, tensions and cements can offer our above-ground architects all sorts of ideas. If we had new evaluations of the materials being used, that could give us some lessons in building.
From the past we had mud and stud (or wattle and daub, or wood and sticky soil), yet there could there could be all sorts of other constructions. After all the whole pottery industry is based on clay. In terms of living components, we will see that nearly four hundred million years ago, there were already 'gluey substances' around. |We also know that oribatid poo is an 'integral part of soil structure' (Behan-Pelletier, 1998). There will be all sorts of cements and glues holding peds and particles together. Look at this super glue - a fungul filament holding a nematode. What else is helping the soil stick together?
Art Deco architects could embrace taller buildings with intricate designs, and modern art deco style because there were new materials like stainless steel, reinforced concrete, plate glass, chrome plating, plastic and mass-produced aluminium. These stronger materials meant there could be more geometric designs. What wonders await in the underworld?
Surely there are substances in soil that could be put to better use than the tons of waste soil that go to landfill in the UK. 95% of total 'Waste To Landfill' from construction sites was classed as soil and stone - making up nearly a third of all waste to landfill. Each ton costs over £100 in landfill tax or over £150k per 'project'. Surely somebody with more wit than I could work out a way of turning that waste soil into usable construction materials?
Soil Scape
As we start thinking about 'architecture' of the buildings, we may be able to see a wider landscape. Those buildings will be linked by roads, rail, rivers and canals. ‘Soilscape’ could convey the widespread underground architecture we are learning more about. This variety of living spaces provides a resilient and stable environment for underground organisms to evolve. Until it is ploughed up.
We talk about landscape architecture about how the land is carved about. We need the term to sum the same underground. Soilscape could convey the massive mass of lie in the architecture that goes on universally underground.
How did this soilscape, this underground universe, come to being? We only only just stating to realise the potential of this universe. It is more sensational than any a scifi universe, made-up world. And it under our feet.
Soil structure
Soil is a porous matrix, not just a collection of aggregates. The structure of soil is important for not only understanding soil functions, such as water and nutrient cycling, and climate regulation, but how soil organisms interact. Increasingly I'm seeing the 'structure' less like a scaffold and more like a skeleton.
Soil architecture dynamics over time are important for biological activity and explaining the volution of soils over millions of years.
Soil pore space
The pore space in soil is seen increasingly as important for finding out how all the soil organisms interact, and the various tensions and chemistry that make soil a continuous dynamic. The pore network, or matrix, can be characterised by pore sizes that are connected which affects the accessibility of organisms and the distribution of water and gases.
Soil health
Soil health is used to make the connection between health of humans and other organisms with soil. More direct connections between human health and soil health are being made, especially when it comes to gut biomes and soil bacteria. Healthier soil improves water infiltration, carbon sequestration, and wildlife habitat. I run a sister website at soilhealth.org.uk, which I had setup to support the first module of a Masters in Regenerative Food & Farming I wrote for Schumacher College, and approved by Plymouth University
Soil health indicators
Nematodes are microscopic worms that can be used as a biological indicator of soil health. The proportion of different types of nematodes in the soil can indicate how healthy the soil is. Other indicators could be springtails or mites, or their predators - like Mesotigmatid mites.
I recommended ground beetles as an easier indicator on BBC Gardeners world
Using "health" in the context of soil, draws an analogy between the condition of other living organisms and the soil.
More on Soil Health Indicators on sister site
Soil Health
Soil Health
In recent years the term 'soil health' his being used. This reflects a 'holistic understanding' of the soil's condition and its ability to function effectively in supporting life.
The term "health" is often associated with the overall well-being and vitality of living organisms, including humans. By using "health" in the context of soil, it draws an analogy between the condition of soil and the condition of living organisms, emphasizing the importance of soil as a living and dynamic system.
Soil health also goes beyond a narrow focus on nutrient levels or physical properties, and encompasses a more comprehensive assessment that includes the biological, physical, and chemical aspects of soil. It enforces the idea that soil is not just a static substrate but a living ecosystem with complex interactions and functions.
Describing soil as "healthy" suggests that it is capable of performing its essential functions effectively. Healthy soil can support plant growth, retain water, cycle nutrients, and provide a stable foundation for ecosystems. This aligns with the idea that soil, like a healthy organism, is capable of fulfilling its role in sustaining life.
It also implies a dynamic and adaptive state, suggesting that soil conditions can change over time in response to various factors. It reflects the understanding that soil is not a static entity but undergoes processes of regeneration, degradation, and adaptation.
"Soil health" is increasingly used to help communicate the importance of soil in a way that is easily understandable to a broader audience, including policymakers, farmers, and the general public. It conveys the message that maintaining the well-being of the soil is crucial for various ecological and agricultural outcomes.
The term "health" generally carries a positive connotation, implying a desirable state. Using this term may encourage a positive mindset and motivate stakeholders to adopt practices that contribute to the well-being of the soil.
In summary, the use of "soil health" reflects a comprehensive and dynamic perspective on soil, emphasizing its living nature, functionality, and the interconnectedness of its various components. This framing helps convey the importance of sustainable soil management and encourages practices that promote the overall well-being of this vital resource.
A particular as of soil health is the ability of soil 'to breathe'. 'Healthy' soil needs air to function properly. Soil can live without air, but is not so productive. The concept of breathing is helpful when explaining how clogged, flooded or compacted soil functions. It can but not very well. Like our lungs, the soil needs airspaces with water films for the exchange of chemicals. See more on my site www.soilhealth.org.uk
'Soil health' is a crucial concept in regenerative farming, something we'll examine at the end of the evolution of soil.
If soil science can evolve over a couple of centuries, imagine what could happen with real soil over hundreds of millions of years...
Facade Prototype click for original
Paradigm Shift
Paradigm Shift
We are undergoing a paradigm shift from 'Dead dirt' to 'Microbe Mush. Now we need to shift to 'Soil Civilisation'
For many years of my scientific upbringing, we were taught about soil as if it were a lump of 'dead dirt'. It was static, stable and really just a substrate, mainly for chemicals
We are now looking at soil more as a continuous flow of life., dominated by microbes moving around. This is exemplified by the wood wide web, which sees soil more as a 'microbial mush'.
Towards a New Soil Science
Soil Civilisation
Soil Civilisation
This site tries to see into soil as a structure with spaces, of innumerable sorts of architecture teaming with life - where there are cities making up a whole civilisation. We will see how the parts - all sorts of constructions made of cements and other building materials joined together by roads, rivers, and canals in a countryside full of features and characters doing all sorts of things - together
Perhaps, we need a paradigm shift in our thinking to a new science (soilology?), that explores that soil civilisation. In the continuing evolution of soil science, we could pick up on Shaler's dream, with a new way of seeing soil. This may help us see how soil could save this planet, but that is for much later.
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