A Soil Primer Looking Closer, Digging Deeper

16 May 2012
Read time: 10 min
Category: Archive

Appearing at least 3 billion years ago, bacteria are the earliest form of life on Earth. Bacteria are single-celled organisms reproducing by single cell division. One bacteria can produce 5 billion offspring in just 12 hours with enough food. Bacteria grow in every habitat on Earth: in soil, acidic hot springs, radioactive waste, water and deep in the Earth’s crust, as well as in organic matter and the live bodies of plants and animals.

When talking about healthy soil we must talk about the microorganisms completely responsible for making it healthy. More than half of all organisms alive are decomposers living under the soil. In one gram of undisturbed soil there can be up to 4 billion bacteria, and on Earth there are approximately five nonillion bacteria – that’s 5 followed by 30 zeroes! Bacteria are vital in recycling nutrients. A teaspoon of healthy garden soil contains as much as one billion invisible bacteria, several yards of fungal hyphae, several thousand protozoa and a few dozen beneficial nematodes. Additionally, 10 to 50 earthworms per square foot naturally inhabit soil when all these other soil dwellers are present.

Second only to fungi, bacteria are among the earth’s primary decomposers of organic matter. Without them, we would be smothered in our own wastes in a matter of months. Rarely dying of old age, most are either eaten or killed by environmental changes and then consumed by other decomposers, often other bacteria. Bacteria do not have mouths, instead they intake food directly through their cell walls, composed of proteins which assist this molecular transport. This is also how human cells absorb nutrients. Once inside the bacteria, the nutrients are stored until something eats them or they die.

In every drop of water are tiny organisms, distant relatives of the cells which constitute the human body, cells still needing water to live inside our bodies. Like bacteria, cells absorb nutrients, excrete wastes, reproduce and die. Bacterial cells are much smaller than human cells, and there are at least ten times as many bacteria as human cells in the body. Humans are made up of an estimated 100 trillion bacterial cells, and only 10 trillion human cells. We are essentially multi-celled beings comprised of trillions of single-celled organisms.


One hundred years ago, topsoil in some areas of the Great Plains measured nearly a dozen feet deep. Today, we measure remaining topsoil in inches. In some areas, less than four inches remain, and in extreme cases the land has become desert. Sudan and Ethiopia used to be 40 percent forested land with more than adequate food supplies for their people as late as 1940. Today they are both nearly 100 percent desert due to over-farming and over-development.

Industrialized civilizations have taken over the entire planet, destroying the majority of the habitats of trees and killing off 90 to 95 percent of all species sharing this planet. We live in what is called The Sixth Great Mass Extinction. Species are becoming extinct 1000 times faster than during any prior age, all of it directly due to pollution and habitat destruction. We have done no differently to soil life. We need to feed the microbes by returning the organic matter we took out.

Disregarding the existence of microorganisms and the role they play in the life cycle, mainstream agriculture uses chemical fertilizers to meet the basic needs of plants without feeding the microorganisms in the soil, whose waste products are natural plant nutrients. Soil becomes lifeless due to a lack of organic matter and minerals to feed microorganisms, leaving nothing available to continue the cycle. Since no food is supplied to the microorganisms, they die or migrate in search of food. Too much fertilizer will cause indigestion in the soil and kill the microorganisms due to excess gas. While chemical fertilizers tend to run-off into the groundwater, bacteria attach themselves to soil particles and the nutrients remain in the soil. Furthermore, chemical fertilizers are salt based and therefore irritants, and the gut microbes responsible for worm digestion die when fertilizers are ingested. Additionally, when soil microbes come in contact with fertilizers, they experience osmotic shock: water in the cells of the organisms burst through the cell walls and kill off the microbes that hold and cycle nutrients.

Fertilizers are the equivalent of taking synthetic chemical vitamins and mineral supplements instead of eating nutrient-dense food. It is not a replacement for real food. Fruits and vegetables and plants might look healthy on the outside when fertilized, but they are not getting the proper balance of nutrients and lack the taste that only the minerals unlocked by microbes can supply. Adding extra fertilizer, especially nitrogen, to the soil often has the unwanted side effect of causing rapid decomposition of the soil organic matter. In the short term, the crop yields will increase, but inevitably, the soil dies.


The conventional way to build new soil is to rotary-till or plow the topsoil and subsoil and mix it together to supposedly create a deeper topsoil. However, tilling and plowing actually creates an inferior soil lacking organic matter and tilth. Plowing thins the soil, making it susceptible to blowing and washing away. After years of tilling, all the fine topsoil is gone, the field surface is several inches lower than before and what remains is gravelly sand and sandy subsoil. Roto-tilling also encourages weed growth by exposing weed seeds to the light required for germination.

Tilling also kills the soil life that turns organic matter into the humus which enriches the soil and feeds plants. Mechanical soil turning methods destroy worm burrows and earthworm populations, which are valuable to soil health. Enriched by the secretions in earthworms’ digestive tract and calciferous glands, their castings are five to eleven times richer in plant nutritional value than the raw materials they eat. These castings have 7 times the amount of phosphate as regular soil, 10 times the available potash, 5 times the nitrogen, 3 times the usable magnesium and 1.5 times higher levels of calcium. Worms deposit 10-15 tons of castings per acre per year if allowed to.

Additionally, Earthworms, bacteria, fungi and others eat organic matter and turn it into humus, which holds three times its weight in water. Humus acts like a living sponge holding a reservoir of water and releasing it slowly for plant use. Soil with a high population of earthworms can absorb a two-inch rain in 12 minutes, while a soil without earthworms will take 12 hours to absorb a two inch rain. When soil becomes too dry, many soil bacteria become dormant. Understanding how microorganisms create healthy soil helps us understand how they similarly function inside the human body. Similar to human cells, they require moisture to assimilate nutrients, release wastes, move about and transport the enzymes used to break down organic matter.

Soil and human bowels

Insects and bacteria turn death into life. Insect tunnels in soil parallel our circulatory system; arteries in the soil make the flow of nutrients possible. In the human body, the colon has the greatest number of bacteria and the most variety of species, and the activity of these bacteria make the colon the site where more metabolic activity takes place than in any other organ of the body, just as in the top few inches of soil.

Many of the bacteria in the digestive tract, collectively referred to as the gut or intestinal flora, break down nutrients such as carbohydrates which humans otherwise could not digest; similarly in soil, a plant cannot absorb nutrients without bacterial help. Fungi, protozoa and yeasts such as Candida, are also present in the human gut. Some plants need fungi to produce strong acidic enzymes capable of digesting tough cellulose instead of the alkaline action of bacteria; so too in the human body, different organs need acidity to digest food while other times alkalinity is needed.

Unfriendly bacteria – both in soil and in human intestines – will breed in anaerobic conditions, where there is little or no oxygen, emitting foul odors and killing off beneficial aerobic bacteria requiring oxygen. Aerobic bacteria are not normally known to cause bad smells. In fact, certain kinds produce enzymes that give soil its clean, fresh, earthy aroma. When these beneficial bacteria are in the intestines, human feces lacks its rank odor; a foul smell, indicates the presence of pathogenic bacteria feeding on foods like meat and dairy.

Other parallels: cancer and disease thrive in anaerobic environments both in the soil and in our bodies. Air nourishes the beneficial soil organisms while keeping harmful bacteria in check. The high temperature in a compost pile kills off pathogens, like a fever in the human body defends against pathogens causing infection. Like the healthy practice of repopulating the gut with friendly bacteria after a treatment of pharmaceutical antibiotics, compost quickly replenishes an area of ground with microbes supporting a soil food web. Properly made, compost contains the entire spectrum of soil food web microorganisms: fungi, bacteria, protozoa and nematodes. It is also full of organic matter, providing living space and nutrients for the microorganisms it contains.

Putting it all together

The Sun is the source of all food on Earth – humans and animals cannot generate food from light, only plants can do this and feed animals. The remains of plants and animals feed worms, bacteria and fungi, which in turn feeds vegetation. By returning unused plant material to the Earth, we feed the microorganisms in the soil. Invisible microbes are involved and responsible for feeding plants. Soil food web gardening requires that the soil be disturbed as little as possible to keep these microbes alive and well. Yard and garden care cannot be only about the plants. We must understand the existence, role and needs of microbes if we are to partner with them in growing healthy plants. Like the Dr. Seuss book Horton Hears a Who?, microbes are down there and want to be heard! They are the ones we need to properly feed. If we take care of their needs, they will take care of ours. Happy Gardening!

Vol 29 Issue 4 Page 34

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