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Save Your Soil

Plants & Gardens News | Volume 23, Number 1 | Spring 2008

by Medi Blum

In all the media reports of dwindling natural resources like fossil fuels, water, and wildlife, there’s a very important resource being overlooked—soil. Every year, over three billion tons of topsoil, the fertile, biologically rich top layer of dirt in which plants grow, erode into waterways in the United States. Topsoil is an extremely slowly renewing resource—it can take over 500 years for one inch of topsoil to generate. Without fertile, healthy topsoil, agriculture, clothing production, and countless other mainstays of human life are imperiled. And the increased storms and droughts forecasted to coincide with global climate change mean topsoil is even more likely to face erosion via water and wind.

Here are some ways in which you can take part in soil conservation on the
home front.

Prevent Soil Erosion

Twice-a-year mulching holds moisture in the soil during the summer and keeps plants warmer in the winter and also prevents rainfall from eroding away your topsoil. Leave the leaf blower in the tool shed—permanently. Leaf blowers can erode topsoil just as fiercely as strong winds, and moreover, they burn fossil fuels. Consider mowing or cutting up fallen leaves to create leaf shreds. Layer these under bark chips and create a feast for soil-dwelling creatures, which will reward you with nutrient-rich, aerated, and moisture-retentive soil that is less prone to erosion. Or simply leave fallen leaves where they lie for an all-natural,
labor-free mulch.

Cover crops are another great practice. Also known as green manure, cover crops like winter rye (Secale cereale) and alfalfa (Medicago sativa) aren't just for farmers! They help hold topsoil in place during the fall and winter and give your ground a nutrient boost. (Just be sure that whatever cover crop you plant is not considered invasive in your state. Check online at plants.usda.gov/java/noxiousDriver.)

Compost

Composting not only makes sense from a gardening perspective; it's also an extremely important environmental practice. According to the EPA, a startling two-thirds of the solid waste stream consists of organic materials like kitchen scraps, yard trimmings, and paper products. Once in a landfill, this stuff festers in bags and breaks down without oxygen (anaerobically) to produce methane, a gas implicated in climate change. You can compost most of this waste yourself, making valuable "black gold" that adds to your available topsoil, feeds beneficial organisms, and makes plants grow faster and hardier. There’s really no reason not to compost what you can.

One excellent resource on composting is BBG's handbook Easy Compost: The Secret to Great Soil and Spectacular Plants (2005 edition). Worms Eat My Garbage (Flower Press, 1997), by Mary Appelhof, is the canonical guide to vermicomposting, which you can do with minimal space. There are countless websites devoted to turning your trash into treasure. For starters, try the EPA’s site; the USDA’s Natural Resources Conservation Service; and BBG’s Urban Composting Project page at bbg.org/compost.

Go Easy on Fertilizers and Pesticides

By amending your soil with compost, you will not need as many fertilizers or pesticides in your garden. Healthy soil can prevent pests and disease from harming your plants and also provide ample amounts of nitrogen, phosphorus, potassium, and other necessary nutrients. Before adding anything to your soil, test it yourself or have a professional soil test performed on it to determine what, if anything, you need to amend it with. (Your local cooperative extension can help you with any questions you may have about soil tests, and it can often also perform tests for you.)

If you do choose to use a fertilizer, try to use natural, organic fertilizers and ones labeled "slow-release." "Quick-release" fertilizers can be swiftly washed out of your garden by rain and may end up polluting groundwater.

Pesticides also pollute waterways and can be harmful to the millions of creatures that inhabit soil and perform in the complex process of decomposition that makes soil fertile. Instead of using chemicals to eradicate pests, use plants as your pest controls. Aphids are repelled by mint, coriander, and chives; cabbage worms dislike sage and rosemary; mice flee from onions; and slugs shrink away from wormwood.

Spread the Dirt Knowledge

On July 19, 2008, the Smithsonian Institute will open Dig It! The Secrets of Soil, an exhibition in partnership with the Soil Science Society of America at the Natural History Museum in Washington, D.C. Visit the exhibit, or e-mail your friends the link to NASA’s Soil Science Education page How Much Soil Is There?.

Do your own research on soil conservation and talk to other gardeners and friends about what you’ve learned. A simple conversation could persuade your relatives to start a compost heap. Soil conservation at home is not only great for your plants but also helps you reduce your ecological footprint.

Medi Blum is the editor of Plants & Gardens News.