Welcome, budding soil scientists. We have arrived at the Significance of Soil – Part II, and we are about to get our hands dirty in defining soil.
In our previous post, The Significance of Soil – Part I, we took a trip through history, discovering our human relationship with soil. But one could argue, that this is not the true history of soil. Where does soil come from? And while we’re at it, what exactly is soil?
In this post, we will look deeper into the significance of soil; into the different types of soil, and their forming factors. We will also look back at the Dust Bowl of the 1930’s, a historic example of what can happen if we mistreat this precious resource.
The problem with defining soil, is that it isn’t specific to one field of science. As we saw in the last post on the significance of soil, the most well-known history of soil, is in its relation to agriculture. However, soil is so much more than a means for growing our food.
The definition of soil depends on the perspective of the field it pertains to. Engineers define soil as the loose material found above bedrock. Geologists, on the other hand, include parent rock material and physical weathering in their definition. An environmentalist is more likely to discuss soils ability to store carbon, and the implications that has on global warming. Whereas, a doctor might relate soil to the organic matter it contains, including life-saving antibiotics.
Soil is interdisciplinary by nature, as it is intricately-connected with everything around it. To better understand what soil is, let’s take a step back and discuss where soil comes from.
The Rock Cycle
The rock cycle is the process through which the weathering and degrading of old rocks forms new rocks. External forces, like temperature and pressure, initiate the cycle. These forces move the minerals that make up the rocks through different states. Through physical and chemical weathering, rocks are broken down into soil. However, weathering is not the only factor in soil formation.
The Five Soil Forming Factors
In the 19th century, a leading Russian soil scientist named Vasilii Dokuchaev clumped the formation of soil into these five factors:
As we just discussed, the weathering of rocks is one of the main actions propelling the rock cycle. Weathering falls under the climate category of soil formation, and can occur in two ways: (1) by mechanical force or (2) by chemical reactions.
The mechanical weathering of rocks is the physical degradation into smaller and smaller fragments. Chemical weathering on the other hand, uses chemical reactions to alter a rocks composition and physical characteristics. Other climate factors in soil formation include temperature, rainfall and moisture, and the leaching of water.
The position of the soil on the landscape also directly relates to its formation. Other topographical factors include slope, elevation, water movement, and soil drainage. For example, soil forming at a great elevation with a steep slope, will be a much drier soil than a soil forming in a valley basin.
All living organisms influence the materials they reside within. The organisms living in soil connect so intricately that they are collectively known as the “soil food web”. These organisms can physically alter the soil, like a mole churning up soil as it moves. Or they can chemically alter the soil, like bacteria changing the acidity of the soil through microbial activities.
Earthworms are especially useful in the formation of soil. They mix up the soil as they move, aggregate the soil through their secretions, and concentrate nutrients in the soil that they eat.
4. Parent Material
The formation of soil also depends greatly on the material from which the soil comes. Soils take on the characteristics of their parent material. Take black sand beaches for example, where the unusual black sand is derived from its dark, volcanic rock parent material.
The formation of soils is a gradual process that takes many years (hundreds to thousands of years for a mere centimetre). Over time, soil characteristics change due to the addition of organic matter, moisture, and other environmental factors.
Each soil has had its own history. Like a river, a mountain, a forest, or any natural thing, its present condition is due to the influences of many things and events of the past.
— Charles Kellogg
Types of Soil
Once soils form, they can differentiate by chemistry, horizons, and particle size.
Soils can be characterized by how they react in certain chemical environments. Cation exchange capacity (CEC) is a seemingly complicated term that is discussed in soil chemistry. What you should know, is that cations are positively charged ions in the soil, and the amount present depends on the amount of clay and organic matter in the soil. CEC is directly related to pH, water holding capacity, and potential mineral deficiencies in the soil. It is the CEC that determines the nutritional needs of a soil, and what supplements the soil needs to be healthy.
Soils can also be characterized by their location in a land profile, which is dependent on composition and their depth from the surface. The layers that make up a soil profile are called horizons, and are identified by the letters A, E, B, C, O and R. Each zone has a different composition, and has different influences on what type of life that soil can support.
Most commonly, soils are characterized according to their structure. Soil structure can be broken down into the types of particles that make up the soil, and the spaces between these particles (the porosity).
Soil particles can be classified as sand, silt, or clay, depending on their size. Sand particles are the largest in size, while clay particles are the smallest. Though this may seem like another dated textbook definition, these particles and their ratios in soil, are what allow air and water to flow, roots to penetrate, and organisms to move through the soil. Having the ideal air-to-water ratio can promote root growth and allow for sufficient drainage, resulting in strong, healthy plant growth.
So now that we have discussed the different types of soil and where they come from, the logical next question is, how are we losing soil at such an alarming rate?
There are many areas of agriculture that can be held responsible for the loss of healthy soil, including erosion due to the rapid harvesting of crops. We will look at these areas more closely in our next article on Soil Loss, but to start, let’s take a look at a devastating example of soil loss in history.
for those who cannot learn from history are doomed to repeat it–George Santayana
The Dust Bowl (aka. The Dirty Thirties)
The Calm Before the Storm
After World War I ended in 1918, the United States and Canada had 10 years of a flourishing economy. There was a peace in the land, and hope and optimism poured into the working class. Factories and farmlands became machines of production, and money was confidently borrowed to invest in a certain, bright future.
Depression and Dust
But this explosion of production was too much for the economy and the land to handle, and in the following 10 years, it all came crashing down. Many people were left in shock, with no jobs, money, or food to support their families. The economy was in ruins, and unsustainable agricultural practices had left the land angry.
This was the Great Depression, and it was devastating. Then, multiple droughts hit. The land dried up, crops stopped growing, and all that was left was dust.
Then came the wind. Wind that picked up the dust, fueling storms that blackened the sky.
Then sickness. “Dust Pneumonia”, children coughing and choking on the air around them.
And death of livestock, blinded and unable to breathe, with stomachs completely filled with sand.
Imagine static electricity– so strong that a simple touch, like a handshake or hug, could generate enough force to knock two people down.
This was the Dirty Thirties, a time when even basic life processes, such as breathing, were threatened. Thousands of people died, in a suffocating darkness that descended for days on end, on and off, for almost a decade. Many people believed that this was the end of the world.
Who is Responsible
The Dust Bowl was a mixture of consequence and circumstance. Droughts were not uncommon to the plains, and with a 6-foot-deep layer of topsoil covered in vegetation, the land had once been able to protect itself from erosion.
This protection was lost when generations of farmers began to ignorantly use and abuse their land. Farming practices displaced grasses and roots that normally held the soil and moisture therein, exposing the precious soil to the harsh elements.
And harsh they were. Extended droughts dried up the land, and high winds and waves of heat expedited the process. Static electricity built up between the earth and the dust, and dust particles were propelled to 10,000 feet, amplified by high altitude winds. The storms began to fuel themselves, and at the time, all hope seemed lost.
I doubt if [the prairies] will be of any real use again.– Prime Minister Mackenzie King
Eventually, it did rain. And eventually, the government took action to help farmers heal the land. Trees were planted as windbreaks, and more sustainable farming practices were put in place, to prevent such destruction from occurring again.
It wasn’t long until, in the 1950’s (aka. The Filthy Fifties), another drought hit the land. This time however, the conservation techniques and restoration projects taken on by the government, did help to mitigate the damage.
Looking back at these events, we should be reminded of the power of an abused earth. The soil that we have is a non-renewable resource, and needs to be protected at all cost.
We should also gain hope from these events, that government action and sustainable farming practices CAN help save our land. The market for organic food and crops is growing, and as more farmers transition to organic, we will move closer to a happy equilibrium.
How can you help?
Soil is the common thread and the often-forgotten link between all the cycles that sustain life on our earth.
Treat your soil right. Help it to retain moisture, form vast root and fungal networks, and gain all the nutrients it needs. Not only will your cannabis plants thank you for it, but so will our planet.
Be it deep or shallow, red or black, sand or clay, the soil is the link between the rock core of the earth and the living things on its surface. It is the foothold for the plants we grow. Therein lies the main reason for our interest in soils.
-Roy W. Simonso
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