Soil solarization

By Tammy Jones
Saturday, August 18, 2007 9:27 PM PDT

Would you be interested in destroying virtually every kind of harmful insect egg and larvae in your garden’s soil? What if the process was easy, cheap and carried many other benefits along with it? Solarization is a simple, five step process that kills insects, plant diseases, nematodes, harmful fungi and even weed seeds. Also, at the same time benefiting helpful microorganisms in the soil, possibly due to lack of competition. Soil that has been solarized allows plants to draw on the nutrients easier especially nitrogen, calcium and magnesium. Seeds germinate quicker. Plants grow faster and stronger, some even mature faster leading to much bigger yields than in unsolarized soil.

Solarization works in much the same way as a greenhouse, where a transparent covering — in this case 3 to 6 mm plastic sheeting — traps the sun’s heat. After a couple of days of sunshine, the soil temperature can rise as high as 140 Fahrenheit at the soil surface and well over 100 Fahrenheit as far as 18 inches down. It takes four to six weeks of sunny weather to completely clear the soil. For most of the country, that means spreading the plastic somewhere between the end of June and the first of Sep-tember.

The size of garden — down to a 3 foot wide bed — will retain enough heat to get the job done. But, the larger the area is, the more heat is generated and maintained, even the benefits are longer lasting. It’s easier to lay down the plastic in a narrow strip rather than a wide patch. The plastic is the solitary expense in using the sun’s energy to improve your soil. You will need a strip or roll of clear (not black) plastic large enough to cover your area and overlap on all sides by at least a foot.

Here are five steps to purifying your soil:

Prepare the soil. Pull any weeds and old crops. Turn in any soil amendments you want to add and then rake smooth. It’s important to remove stones or clumps that might raise the plastic and create an air pocket resulting in uneven heating.

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Water thoroughly. Leave a sprinkler on for several hours, or even overnight to soak the soil. This creates 100 percent humidity under the plastic, which with the heat, will kill all those unwanted beasties.

Dig a trench all around the bed, or plot 6 to 8 inches deep.

Lay a clear, plastic sheet which is 3 to 6 mm thick over the are, overlapping the trench on all sides. Fill in the trench to weigh down the plastic, and pull it as tight as possible.

Sit back, relax and wait. Cloudy weather will slow things down under the plastic, but a few weeks of sunshine will dramatically improve your soil, easily and cheaply.

I hope this gives everyone a good idea how to easily clean-up an area you would like to use.

Remember, I would love to hear what you’re interested in, and what you would like to read about so, e-mail me at kntjones@mindspring.com.

Hope everyone has enjoyed their garden this year. I added a butterfly garden and birdbath, and my family has really enjoyed watching the birds that have shown up and the ingenuity of the squirrels.

Well, good gardening!