Prevent Weeds With Solarization

Try a solarization, an organic gardening alternative to commercial pesticides and herbicides.

| May/June 1982

For those of you who cringe (and rightly so!) at the thought of applying harsh chemicals to the same soil that'll bear your family's yearly harvest of fruits and vegetables, yet who don't want to leave the garden plot vulnerable to a host of wintering-over pathogens or spend your summers fighting a thick carpel of weeds, there may be an effective (and amazingly simple) solution to your problem.

There's a new technique, you see, currently being researched by farmers and gardeners throughout the country — including MOTHER EARTH NEWS' own Kerry and Barbara Sullivan — that uses the sun's rays to kill bacteria, fungi, weed seeds, nematodes and such. The procedure, called solarization, consists of simply soaking the ground with water and then covering the wetted area with 1-to 6-mil clear plastic sheeting. (Naturally, you'll need to weight down the edges to prevent the plastic from blowing away.)

The covering produces a greenhouse effect on the soil, and heats the ground beneath it to temperatures between 100 and 140 degrees Fahrenheit. After four to six weeks of this solar conditioning, the soil should be cleansed of most weed seeds and pathogens without chemical contamination. What's more, the "pasteurized" earth is — if early studies prove true — actually more productive than ordinary loam.

How Solarization Works

There are several perfectly logical explanations for the success claimed by proponents of this method. For one thing, the sunlight shining through plastic heats the topsoil enough either to kill outright or, under less than ideal conditions, to germinate any preexisting weed seeds (or other spores) that might be harmful to new vegetable seedlings. Then, as the unwanted sprouted seeds grow, the shoots are destroyed by the continued high heat.


The reported increases in soil productivity could well result from the anaerobic situation that's created by watering the ground and covering it with airtight plastic sheeting. Any living matter that requires oxygen, then, will die while those organisms not in need of oxygen will thrive and — it has been suggested — speed up the decomposition of any organic matter present in the soil.

3/24/2014 6:26:17 PM

I am surprised that no one has commented on solarization. I accidentally solarized my garden one year when I covered the plants in a plastic sheet to protect them from a hailstorm. I forgot to uncover the plants the next day and they all died. I tilled the soil and planted a nice crop of collard and kale on the site for winter greens. The problem that I had with that site was woooly aphids. Wooly aphids covered every inch of the plant for the past several years. Neem oil controlled them but they were still a very real over opulation disaster. After the accidental solarization, I did not have as many problems with the aphids. At first I thought the answer was in the death of the plants, but after reading this article, I believe the answer was in the solarization itself. I let different spots in the garden rest from season to season. The overgrowth of burmuda grass is a very real problem. I will try solarizing a section of the garden to see how the solarizing affects the burmuda grass. I too have a concern about the beneficial life in the soil but if the solarizing helps other life survive to be helpful, then the solarizing is word a try.

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