Soil Solarization: How To Kill Soil Pests and Diseases

Have you ever heard the term soil solarization? It’s a process allowing home gardeners to capture and use the energy from the sun as a soil pest control mechanism.

Gardeners lay a clear plastic tarp, black plastic sheeting or clear polyethylene atop garden soil.

killing pests with soil solarizationPin

The solar energy is concentrated on the top 12″ to 18″ inches of soil. This effective, simple technique is referred to as soil solarization.

The Benefits Of Soil Solarization

For home gardeners the greatest benefit of solarization is weed control.

The best results near the soil surface and decrease with depth. In the top 6″ inches of soil, the trapped heat below the layer of plastic film can reach high temperatures of 140° degrees Fahrenheit and above. This intense temperature from solar heating kills:

  • Insects
  • Root-knot nematode
  • Soil-borne pathogens
  • Weed seeds
  • Various bacterial and fungal pathogens
  • Fungi
  • Other disease-causing organisms

Why does this matter?

These are the pests and pathogens that cause:

  • Potato scab
  • Verticillium wilt
  • Crown gall disease
  • Fusarium wilt
  • Phytophthora root rot
  • Other soil-borne diseases

Solar Radiation Mimics Soil Fumigation

Solar soil sterilization mimics soil fumigation without using soil fumigants like methyl bromide and kills beetle grub worms and soil pathogens. It is a general biocidal treatment.

This natural method offers significant soil sterilizing benefits. However, it puts your garden out of commission for 4 to 6 weeks in the hottest and sunniest time of year. This period is usually the peak growth period for most garden crops.

In areas such as California, the growing season is relatively long. Solarized soil can be done during the summer and follow up with a fall garden crop.

In other areas, you can partially sterilize the soil if your garden is large enough. Partial solarization is sterilizing one part of your garden and actively garden the rest.

If soil pests are particularly a bad, you can choose to forego gardening for one year and bake the soil to sterilize instead.

Related: Can you reuse Potting Soil?

Soil Solarization A Simple 4-Step Process

Step 1: Cultivate the soil area you want to solarize, then collect and dispose of dead plant material along with other debris that harbor pests.

Step 2: Smooth and level the surface of the soil

Step 3: Supply water to the soil properly to a depth of at least 12 inches. This ensure that soil heating conductivity will increase.

Step 4: Lay black plastic sheeting, plastic mulch or a garden tarp on the surface of the soil. Next, anchor the edges of your tarp using soil.

The closer your tarp is to the surface of the soil, the better the soil temperature will be. After 4 to 6 weeks remove the tarp and resume gardening.

Do not keep the plastic on sterilized soil over 6 weeks or it will start to break into pieces.

Does Solarizing The Soil Kill Nematodes?

Mobile pest including nematodes and insects, can escape the heat by simply burrowing deeper into the soil or moving out from underneath the tarp.

The heat concentrated from the solar radiation under the tarp usually kills pest organisms more readily than beneficial soil organisms. Soil borne pests usually die out easier in the absence of plants and plant materials.

Where Solarizing Soil Is Not As Effective

Sterilizing potting soil and potting mix with plastic works best when the weather is cloudless and hot. In the areas that never get too warm or never get much sun, the process may fail to work.

In such areas, solarization can create a greenhouse-like effect and actually encourage growth of weeds

Gardeners in foggy coastal regions and the far north should check with their local extension agent to see if sterilizing soil using the sun works in their area.

Increased Nutrient Availability

Solarization also offers a side benefit of increased nutrient availability. As the irrigated moist soil begins to heat up, the organic matter within it starts to undergo a mild cooking process.

This mild cooking method with use of a solar cooker causes the solid material to start breaking down thereby creating a nutrient-loaded liquid.

When complete, these rich soluble nutrients will be available to your crops usually at a higher rate than they would be otherwise.


Soil solarization is an effective and natural method to control pests in your garden as clearly shown in this article. However, it might not work if you are in areas that do not enjoy too much sun and high temperature.

In addition, it affects gardening activities since you cannot use the areas undergoing the solar and steam sterilization process for gardening.

Still, solarization offers several benefits to gardeners. It offers increased nutrient availability and provides an effective, chemical-free remedy for getting rid of pests and plant pathogens in your garden.

If you would like to try soil solarization in your garden, follow the 4 simple steps described above but ensure that your location meets the ideal conditions.

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