Solarizing Garden Soil—The Benefits and Top Tips for Best Use

The power of the sun—it not only provides us with heat, light, and energy, but it has a range of uses to make life easier, keep things clean, and enhance natural ways of living.  Solarizing garden soil can benefit it in many ways.

Sustainable farming utilizes soil solarization as a way to naturally prevent several farming frustrations, such as bacteria, weeds, and insects. Whether you have a small home garden or you are deep in the sows of your own homestead, you can solarize your soil to reduce weeds quickly and for the long haul.

The Basics of Soil Solarization

Soil solarization harnesses the sun’s power to lessen the presence and effects of crop and farm pests such as bacteria, weeds, and insects. These pests take over the soil, ruin leaves, and steal essential nutrients from your plants.

The first step in soil solarization is to cover the growing area with a tarp, such as a clear polyethylene cover. Doing this traps the solar energy, thus heating the soil. Soil that is heated in this way is less likely to harbor bacteria, insects, mites, weeds, and fungi.

Several other important tasks ensure proper soil solarization:

  • Clear the area. – Make sure that all plants and debris are removed from the soil. If left there, they will block the growth of your healthy plants.
  • Water thoroughly. – The entire soil area needs deep watering; water until the soil feels and stays wet to the touch.
  • Use the right material. – Clear plastic (1-4 ml painter’s plastic works well) is the most efficient. White or black tarps don’t allow enough heat to enter the soil.
  • Secure the tarp. – Bury the edges of the material in the soil so that the heat is effectively trapped without room to escape.
  • Let it be! – Leave the tarp in place for at least a month. If this month is during the hottest part of the summer, even better!

Best Types of Soil for Solarization

Heavy soils respond best to solarization. Heavy soils are made of clay, loam, or a mixture of the two. These hold moisture better than light soils, such as sand. This ability to hold a large amount of moisture enables steam, which effectively kills weed seeds, insect eggs, and nematodes.

Although you could try soil solarization on lighter soil, remember that sandy soil doesn’t hold moisture, so it won’t produce as much steam. If all you have is light, sandy soil, you could use a lay drip irrigation line under the tarp. Then, add water regularly to ensure constant moisture and water availability.

Research Results from Solarized Soil

Texas A&M researchers studied the temperatures of non-treated soil and covered soil according to these techniques. In two concurrent year studies (2011-2012), the covered, sun-treated soil reached temperatures up to 60°F higher than that which was left alone.

The scientists didn’t stop there, however. After realizing that the soil effectively retained heat, they dug deep to look at the germinated weeds. Four weeks after removing the plastic covers, the non-solarized plots had 90 germinated weeds (2011) and 300 (2012). The solarized plots, on the other hand, had three (2011) and 19 (2012).

Even six months later, in the spring, the solarized crop plots only had perennial weeds. The non-treated plots were full of both annual and perennial grass that applied significant pressure, overtaking the desired crops.

What to Look For

If your soil is effectively harnessing the sun’s energy, you’ll notice water droplets underneath the plastic in the early morning hours. These will disappear by afternoon as the water turns to steam.

When you notice a smaller amount of water droplets each morning, that’s a sign that it’s time to irrigate the soil again, ensuring adequate moisture availability.

It’s important to note that although the solarization process effectively kills pests, weeds, and bacteria, it also rids the soil of beneficial organisms. These positive organisms are easily added back into the soil with high-quality compost, which is easily made through your household food waste—another great homesteading project!

Other Weed Deterrent Options

One of the main benefits of soil solarization—besides the free energy from the sun—is the fact that it effectively kills frustrating pests without dangerous and undesirable pesticides. However, there are also other options (that you can combine with soil solarization or use on their own) to rid your crop areas of unwanted organisms.

Stoneycreek Farm recommends natural methods such as ground cover as an effective deterrent against insects, weeds, fungi, and bacteria. Ground cover can include plants such as crimson clover, hairy vetch, and periwinkle.

One of the reasons that ground cover is such an effective weed deterrent is that the covering plants prevent the weed seedlings from absorbing the light, moisture, and nutrients necessary for survival.

Ground cover offers the added benefit of aesthetic appeal to your homestead or home garden. Several choices even bloom into colorful flowers in particular seasons.

Speaking of seasons, certain types of ground cover serve as a temporary cover crop once you’ve already harvested your main produce. Crimson clover, for example, thrives in the winter and keeps weeds from taking over the soil before you plant a new crop. In the spring, the cover crop isn’t wasted. Simply till the cover crop, replenishing the soil with nutrient-rich organic matter—also called “green manure.”

Of course, complete weed prevention is almost impossible. However, the ones that do remain after natural methods such as soil solarization and/or ground cover are almost always small and easy to remove.

Certain types of ground cover overtake areas quite quickly, though. Educate yourself on the qualities and habits of the cover you choose so that you aren’t surprised by its growth.


You can solarize any area as long as you have enough tarp to cover the soil. Remember that solarization works best if your soil is already de-weeded and you utilize the sun during the hottest month of the year. This still leaves you plenty of time to plant so that you can harvest in the fall.