Teach Me About Soil

by James H. Wandersee and Renee M. Clary

Project your imagination into the soil below you next time you go into the garden.   Think with compassion of the life that exists there.  Think of the drama, the sexuality, the harvesting, the work that carries on ceaselessly.  Think about the meaning of being a steward for the earth.
– Marjorie Harris,  In the Garden, 1995

A scientifically literate citizenry is essential if we want environmental activism to flourish. Only after people come to understand why something is precious and finite are they likely to care about saving it. Envisioning a green and sustainable human future is vital to preserving life on Earth.

Soil is Life

Eco Walk the Talk has published several articles about soil. Those of us who value plants and the fundamental roles they play in the biosphere comprehend how precious soil really is.  Each of us who do can help improve the world’s scientific literacy by helping others understand two fundamental ideas about soil: (a) how much even a 21st-century urban lifestyle ultimately depends on the Earth’s limited supply of fertile soil; and (b)  how much richer in meaning the scientific term soil is than the commonly used term, dirt.

Soil is a ecosystem-service-based resource, a living, breathing material matrix that, with proper stewardship, will maintain itself. It’s also our lifeline for survival.   If and when it has finally been depleted, the human population will disappear. Soil is our “green gold” but we are treating it like dirt! Paradoxically, there can be no life on Earth without soil, and, there can be no soil on Earth without life.

A Green Apple can be used to teach about soil

A Visual Object-Lesson That May Help You Teach Others About Soil

1. Hold a green apple (fruit) in your hand. Imagine the apple’s surface is the planet Earth.
2. Cut this apple vertically into fourths. Set three of these pieces aside and look at them. These three sections represent the Earth’s oceans—they help us remember that oceans cover about 75% of the Earth’s surface.

3. Now look at the remaining piece of apple. It serves to remind us that only about 25% percent of our Earth is actually land that people could inhabit.

4. Next, take that land piece of the apple and cut it in half.

5. Of these remaining two halves of land, hold one of them in your hand and observe it. It represents the amount of the Earth’s land (12%) that is not suitable for farming. (This includes places such as mountains, canyons, deserts, lakes, swamps, and the icy Arctic and Antarctic lands.) Set this piece aside.

6. Look at the very last piece of apple, It symbolizes the area of Earth (12%) where people could live and grow crops.

7. Then, slice this last section lengthwise into fourths.

8. Pick-up one of these little apple pieces (3%) and note that it represents the amount of the Earth’s land that is too wet to produce food crops because it can flood during the time between planting and harvesting. Set it aside.

9. Pick-up the second of these little apple pieces (3%).  It shows us the amount of the Earth’s land that is too rocky or nutrient-poor to grow  crops. Set it aside.

10. Pick-up the third of these four little apple pieces (3%).  It stands for the amount of the Earth’s land that is too hot to grow crops. Set it aside.

11. The remaining  section of our apple should help us recall that the total area of the Earth’s land that people use for farming is only about 3%.

Only 3% of the Apple Peeling Represents All of Earth’s Arable Soil

12. Now check this online world population clock website to view today’s world population count. At this writing, that last 3% of land provides “life support” for nearly 7 billion Earth citizens!

13. Finally, remove the GREEN apple peel from that last apple (farming) section. This tiny amount of apple peeling represents all of the Earth’s soil that is available to grow crops to feed our hungry world! It is the growth medium for land plants. That’s why we used a GREEN apple.

Soil conservation is the only way forward to feed the Earth’s burgeoning population.

Note: Our lesson plan for soil was inspired by the work of Victoria Naegele, AAITC.

Some Educationally Indispensable Facts About Soil

Soils affect the quality of human life throughout the world in many ways. Soils are not only the principal resource we use for food production, but they also support for our building structures, serve as the medium for distributing and storing water and nutrients, and form the living foundations for land ecosystems throughout the biosphere.

Some Trees May Have Large-Diameter Root Zones

Soils actually support more life beneath their surface than exists above! For example, half of all plant life exists outside of our field of view. Root systems thrive within the region of soil known as the root zone. (This seldom visible portion of plant life is sometimes called “the hidden half” of plants.) Soils enable organisms to complete their life cycles of growth and decay. Biogeographically, they also help to shape the worldwide distributions of the living species on Planet Earth.

Conversely, living organisms help to form soil. There is no soil on our neighboring planets, Venus and Mars. Why not? Both have plenty of rocks to serve as parent material and both have natural forces to break them down over time. But there’s something essential that is missing. Without life, there can be no soil.  Only Earth has soil, and organisms actually made its soil. What kinds of organisms? Algae, bacteria, protozoa, fungi, plants, and animals.

Soil scientists consider soils to be a natural resource found on the Earth’s surface. They study soil formation, classification, and mapping. They investigate the  physical, chemical, biological, and fertility properties of soils. They analyze these properties in relation to the use and management of the soils.

Erosion is the process by which the materials in the Earth’s crust are worn away and carried off by means of wind, water, and other natural forces. Farm lands are the main place that soil is being lost. Fields planted in rows,  such as corn, are the most susceptible to soil runoff. Where does this soil go? Much of it ultimately ends up in the oceans.

Agriculture depends heavily on the upper 6-8 inches of topsoil. (An inch of topsoil can take up to 500 years to form.) When the topsoil is lost, subsoil is exposed. Subsequently, farmers use more chemical fertilizers (derived from petroleum) in an attempt to make up for the decreasing productivity of the newly exposed subsoil, thus adding to environmental pollution.

Simply put, we must learn to farm without losing the soil—this calls for a more natural approach to soil husbandry with reduced tilling of fields, smaller farms, less monoculture, drastic reduction in pesticide and fertilizer use, more labor-intensive farming, increased use of organic mulch and manure, use of contour plowing, and so forth.

Soil erosion has increased to the point where it vastly exceeds the natural formation of new soil. Professor David R. Montgomery, a respected geomorphologist, a geologist who studies how the Earth’s landscapes change over time, contends that soil is humanity’s most essential natural resource and is essentially linked to civilization’s survival. The best soil for farming is found in the Earth’s temperate zones; the soil in the tropics is not as good and it gets depleted much faster.

Examine This World Map of Soil Degradation

We are running out of soil, and agriculture will soon be unable to support the world’s rapidly growing populationWe think that a genuine respect for soil begins with an understanding of how the scientific meaning of the word differs from the common word dirt.

What’s the difference between soil and dirt?

Simply put, dirt is what you remove from under your fingernails—an unwanted, particulate-based residue of unspecified origin that is considered unclean. Soil is what you typically find under your feet whenever you walk outside. Think of soil as a thin-but-layered living skin that covers most of the land, except for bare rocks.

Natural soils are alive? Yes. Soil may originate from rocks, but it is much more than just rock particles. It includes all the included living things and the materials they make or change. Soil is the combination of minerals, air, water, bacteria, fungi, plants, animals and other life forms (plus their wastes and decaying bodies) that accumulate in layers upon the Earth and become compacted over time. Indeed, soils are laid down in discrete layers whose compositions vary over time and space. For example, over 50,000 types of US soils have been identified, and not all areas of the country have even been surveyed.

Clay soils

Igneous and sedimentary rocks comprise about 66% of Singapore’s geological setting, and thus residual soils resulting from their erosion make up a large part of Singapore’s soils.  Bukit Timah soil is granite-based.  In contrast, Jurong soil has proven to have more of a sandstone and mudstone origin. Both of those are clay soils. Indeed, much of the soil throughout Singapore has been found to be clay, although the origins and processes forming its clay soil types vary by area.  Less prevalent is  Singaporean mangrove swamp soil. It differs because it is a water-deposited mix of clay, sand, and silt—along with some sandy topsoil in shallower areas. Singapore has very little farmable land (4% of the Republic), but its soils obviously support very lush and abundant plant life.

Soil that is separated from its natural location may become dirt—as when we track-in dirt into our house from our garden plot on the bottom of our shoes.  How can it be both? Particles of that soil erode or are dug up are disassociated from their natural environment. They lose the history of their origin—their physical, chemical, biological, and geological relationships with surrounding material, the particles and life forms that were above, below, and to their sides. It’s the integration that makes soil different from, and much more important than, dirt.  You can always distinguish “plant persons” from a member of the general population by the way they use the words dirt and soil. They have a kind of reverence and respect for soil, and they take pains to use the word soil whenever they are talking about plants.

It takes a lifetime of study and experiences to fully understand and appreciate soil, and learning is incremental for all of us. Yet, it is important to realize that practicing environmental stewardship is actually in our own, and our children’s, best interests. We must all work to protect and conserve our soil—because having healthy lives depends upon the quality of the food we eat, the air we breathe, and the water we drink.

Today you drank water that flowed through soil and was cleaned by the soil;  you ate food that was grown in soil; you breathed air whose quality was affected by the gas exchange of land plants rooted in soil; you likely wore clothes made from fibers of plants that grew in the soil; and it is estimated that about 85% of the world’s population uses soil-grown herbs as their primary medicines.

Maybe your situation in life doesn’t allow you to work directly to conserve soil and practice natural soil husbandry. But, all of us can teach others to value and appreciate soil, and to better understand how wonderful it is.

About our Guest Writers:

Dr. James H. Wandersee is the W.H. LeBlanc Alumni Association Professor of Biology Education in the College of Education at Louisiana State University and Chair of the Teaching Section of the Botanical Society of America.
Dr Renee M. Clary is the Director of the Dunn-Seiler Geology Museum and Assistant Professor of Geoscience Education in the Department of Geosciences at Mississippi State University. Both are part of the EarthScholars™ Research Group and have done extensive research in the pioneering area of Plant Blindness and how to sensitise people to plants.

Further blogs you may be interested in:
1. Plant Blindness: What research says by James H. Wandersee & Renee M. Clary
2. The Bridge Between Ecological Knowledge and Green Living by James H. Wandersee & Renee M. Clary
3. Organic Gardening: Importance of Balanced Soils
4. Soil Biodiversity: The Invisible Hero
5. Part 1.  How to compost at home using container pots

6. Watch the trailer of “Dirt! The Movie” which talks about the wonders of soil biodiversity and the degradation of this precious resource


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Posted by on Aug 31 2010. Filed under Biodiversity, Sustainable Agriculture/GMO/Organic. You can follow any responses to this entry through the RSS 2.0. You can leave a response or trackback to this entry

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