Is Your Garden Really Green? Get the Dirt on Your Dirt

By Ric Coggins

Getting ready to plant your organic spring vegetables? Hold that hoe! One of the best reasons for growing fruits and vegetables in your garden is that they are free of pesticides, herbicides and chemicals. Or are they? The answer depends on the current condition of your soil, the previous chemical additions to your soil, and your knowledge of them both. So before you begin, get the dirt on your dirt.

If you just recently became aware of the sustainable advantages of organic gardening methods and have used chemicals in the past years, that is cause for concern. A backyard lawn, long maintained with Roundup and Turf Builder, can be turned into the perfect garden spot, but maybe not this year. If you just moved into a house and have no idea of the previous soil history, your really don’t know how your garden will grow. Organic? Maybe not.

The first place to get the scoop on your soil is to have it tested. A basic soil test determines whether your soil is acidic, neutral or alkaline. It also indicates which elements are missing from your soil and how much to add to remedy the problem. But it does not cover contaminants. In order to get an idea of the real composition of your soil you will need to send in a soil sample to one of Phoenix’s soil analysis and testing laboratories. Collect soil samples, about 6 inches deep, from different areas in the place you wish to garden. Mix the dirt, let dry, then place one cup of the mixture in a sealed container to mail or deliver to the lab.

If you are anxious to get your garden going, you can remove the old soil and replace it with clean soil. The removal can be done with a gardening or tree spade or even a small excavator, which is available for rent from Home Depot for around $180. New soil can be amended and mixed in a wheelbarrow. Amended soil depends on the area’s drainage and intended plants for gardening. This may be an expensive option for some.

An alternative to replacing your soil, if you are determined to get down on the ground for your gardening, is to pursue a soil detox program for your plot. This would also be the process needed before creating a garden that is truly organic.

Time is the first element necessary for a soil detox program. To display the USDA organic label, growers are required to prove three full years with no application of prohibited toxins. This allows nature to take its restorative course. Rainfall and irrigation will leach toxins from the soil to depths beyond the reach of garden plant roots. Soil microbes will break down toxins into nontoxic components. And finally plants growing in the contaminated soil will draw up toxins into their roots, stems, leaves and fruits, doing their share in ridding the soil of poisons.

For those on a faster track, it is possible to assist nature in its cleanup. Soil amendments, microbe products and special plantings can all work together to detox a contaminated garden site more quickly. The application of fine-textured humates, activated charcoal, or zeolite mixed together or applied separately act to tie up contaminants until they can be leached out. Apply these at a rate of 20 pounds per 1,000 square feet.

Organic soil amendments such as compost, worm castings, and even liquid molasses will feed and restore populations of microbes not killed by the toxins. These microbes breakdown the toxic molecules into nontoxic components. Adding mycorrhizal fungi inoculants will also greatly enhance the detox process and create immense soil health.

Plants that absorb soil toxins are another means of detoxifying garden soils. If you are converting a former lawn to a garden spot, the much maligned dandelion may get the last laugh as they are one of the best plants for detoxifying contaminated soils. Maybe more acceptable than a field of dandelions is a sunflower patch. Sunflowers do an amazing job of pulling out toxins, as do mustard greens plants. Of course, I wouldn’t recommend eating any parts of these plants as they will have absorbed the pesticides and chemicals from the soil.

While studying or detoxing your soil, or if you merely want to bypass the dirty work, why not plant a raised garden? Beds are fairly easy to build, and that can be followed by the addition of a perfect soil mix guaranteeing that your crop is contamination free.

Any of these options will lead to solid ground for a healthy organic garden, a hearty harvest, and a healthier you.


Ric Coggins is a University of Arizona Master Gardener (Maricopa County) who grew up on a one-acre garden tended to by his father, who was a regular contributor to organic gardening and farming magazines. Ric continues his father’s “green” traditions, owning and operating The Fool on the Hill Farm, a one-acre organic garden homestead in Mesa.

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