Answer: To solarize soil, you need to start during the hottest part of the summer, and leave the plastic in place for up to 3 months to kill disease pathogens and weed seeds. Start by smoothing out the area (removing sod, plant debris and rocks), moisten the soil, lay a 4 mm to 6 mm thick sheet of clear plastic over bare soil, and seal the edges of the plastic with rocks or soil. This will naturally heat up to over 140 degrees F, which kills most pathogenic organisms in the top 4-8" of the soil, depending on soil type and temperatures.
An easier method is to apply a corn gluten-based herbicide. You'll find these products in gardening catalogs. Gluten is a by-product of corn processing, and has been used in livestock feed, but researchers recently discovered that the gluten includes an enzyme that kills germinating seeds. And to top it all off, corn gluten provides nitrogen to the soil as it breaks down. Nature is amazing, huh? Good luck!
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