Mother Earth’s Soil: Don’t Treat It Like Dirt

—by Emma Onawa

Have you ever thought about the impact of soil in your life? Sure, it gets your clothes and fingernails dirty, you have to clean it off your shoes, and when it rains, mud can be a real hassle. But, compared to what soil does for life on Earth, these problems are the stuff of petty nuisance.

Soil: A Rare Resource

If an apple represented the earth and we were to carve it into its constituent elements: 75% consists of water, 25% consists of land; 50% of that land consists of polar regions, deserts, and mountains, generally unproductive for mass cultivated food production, leaving 12.5% of the apple; 40% of the remaining 12.5% cannot support mass cultivated food production because it’s too rocky, steep, shallow, or wet.

Peel the skin from the remaining 10% and what remains represents the soil we depend upon for world food production, competing with other human needs: homes, office, factories, schools, landfills, etc. (The apple metaphor can be found here.)

Life Underground

Soil is teeming with life. These life forms break down soil and contribute to its fertility. It’s estimated that the weight of bacteria and other micro-organisms in the soil is 25 times the weight of all living animals and other life-forms above the soil. Only 2% of these singlecelled species have been identified and trillions may fit into a teaspoon of soil. These bacteria, worms, insects, fungi, rodents, and a myriad of other life forms may be easily dismissed by humans; but their impact on Earth’s life is immeasurable and priceless. Without healthy soil, all life on the Earth would die.

What Is Soil?

Soil makes up the outermost layer of the Earth and consists of weathered rock and decaying plants and animals. It takes more than 500 years to form two centimeters of topsoil. Soil can filter out and neutralize pollutants and store as much as 3750 tons of water per acre

Soil stores 10% of the Earth’s carbon dioxide. Perhaps of most interest to kids, it makes excellent mud pies.

Sand, silt, and clay are descriptions that refer to soil texture, or the size and percentage of various mineral particles that make up the soil. Sandy soils have the largest particles and clay, the smallest.

The pore spaces in between particles are filled with water and air. Sand, with the largest particles, is the most porous soil. It tends to be less nutrient-dense, and dries out more easily. Clay particles tend to be more nutrient- dense, and hold more water, which can smother plants. Loam refers to a specific mixture of sand, silt, and clay and is ideal for plant life.

Trouble on Planet Earth

Unfortunately, the earth’s soil is in trouble. The use of chemical fertilizers, pesticides, and herbicides has substantially reduced soil health and productivity. Annual monocropping, excessive tilling, failure to replenish soil fertility through natural means, and the destruction of native plant life all contribute to the destruction of soil. These practices result in conditions such as the 1930s southern plains Dust Bowl and similar conditions worldwide today.

Caring for your soil

How can we all get to know and care for our soil? Here are some tips:

Determine your soil texture:

There are a couple of ways to test soil texture. A simple way is to rub a moistened ball of soil between your palms. If it feels sticky and you’re able to make a rope, the soil is clay. A sandy soil will feel gritty when wet and rubbed in the palm of your hand. Silt will feel floury or silky.

A more scientific way to test soil texture can be found at: .

Test and adjust your soil’s pH:

The pH of your soil is a measure of its acidity or alkalinity. pH scales range from 1 (most acidic) to 14 (most alkaline), with 7 being neutral. Each number represents a ten-fold difference in pH level. Soil pH determines the availability of nutrients to a plant’s roots. Most plants grow best with a pH of 6.0 to 7.0. Soil organisms prefer a pH of 6 to 8.

You can purchase a pH test kit at garden centers or have your soil tested by your county extension office for a nominal fee. Mineral amendments, such as lime and gypsum, can be used to adjust pH level, as deemed appropriate.

Amend your soil with organic materials:

Humus is a soil amendment made up of broken down organic materials, such as leaves, grass clippings, manure, and other garden and organic kitchen scraps, as well as ground bark, leaf mold, and wood shavings.

Compost is an ideal soil amendment. A compost pile can be created even on a small urban lot, either through composting bins or in an enclosed area in your backyard. Compost and other soil amendments, preferably organic, also can be purchased at garden stores. Humus helps soil particles to bind together and loosen tight, compacted soil. Once you know your soil texture, you can determine how to amend it.

Love your earth worms and other soil residents:

Earth worms eat soil for its organic matter. Research has shown that the fertility value of organic matter is increased ten-fold by passing through a worm’s digestive system. Earth worm castings (poop) are gold for soil. The health of a soil often can be determined by the number of earth worms living it.

Earth worms can be purchased and introduced to soils that need a nutritional boost. Other organisms that break down organic matter include a variety of insects, protozoa, and microbes.

Refuse to use chemical fertilizers, herbicides, or pesticides:

Chemical fertilizers, herbicides, and pesticides impact soil fertility by killing off beneficial organisms and introducing toxic elements into the soil and environment. The widespread use of these chemicals in commercial farming, while perhaps increasing production in the short term, has the long-term impact of substantially reducing soil health and fertility.

Enhance soil health and fertility with cover crops and crop rotation:

Allowing a garden or portion of a garden to “rest” for a season can help greatly to restore soil nutrition levels. Cover crops, known as green manures, include clovers, legumes (various beans), certain grasses, and vetches. They also protect resting soil from erosion. Cover crops are allowed to mature to a certain stage and then dug into the soil. Since different plants need different nutrient types and levels, rotating types of plants from year to year can help to preserve soil health and fertility.

Limit tilling and other disturbance of soil:

The more a soil is tilled or disturbed, the more its fertility is impacted. Try to work soil no more than once a year and add amendments at that time. Avoid working the soil when it’s too wet or dry and avoid stepping on garden beds, particularly when wet, to minimize soil compaction.

Use a mulch whenever possible:

Mulches help with weed control, soil retention, and temperature control, and enhance a garden’s appearance. Generally, the bigger (and more woody) a piece of mulch, the longer it will last. The type of mulch used depends upon location and what’s being mulched. For perennial gardens and other landscape areas, a more durable and attractive looking mulch may be used. In vegetable and other more “practical” gardens, straw, grass clippings, chopped leaves, and even newspaper (using non-toxic inks) can be used.

Sources:

A comprehensive organic gardening Web site can be found at http://www.organic gardening.com. Click on the "Compost & Soil" tab at the top for soil information.

An excellent print resource is Rodale’s Successful Organic Gardening: Improving the Soil, by Erin Haynes, Rodale Press, Emmaus, PA, 1994.

[Emma Onawa is a veteran member and shopper of co-ops; worships felines; loves gardening, nature, and eccentric people; and investigates esoteric subjects that would put most people to sleep.]