What is Soil Solarization?

GardeningPest Control

Soil solarization uses sunlight and heat conduction to raise soil temperatures and eliminate unwanted pests, weeds, and diseases. This method effectively utilizes the scorching months of the year to prepare the land for a fall garden. Implement this method in your home garden this summer.

Have you ever driven past bare farmland covered with rows and rows of clear plastic? 

No, this is not a growing technique. It is soil solarization, a method of managing pests and diseases in the soil, and it can be implemented in your home garden, too.

The Purpose of Soil Solarization

Essentially, soil solarization is the process of trapping heat from the sun underneath a tight layer of clear plastic so that the soil reaches a temperature high enough to kill unwanted pests, weeds, and diseases. This method is especially helpful for managing nematodes–microscopic worms that damage plant root systems throughout Florida. Soil solarization rids the earth of these undesirable inhabitants for three to four months, effectively utilizing the scorching months of summer to prepare the land for a fall garden.

Pros and Cons

Soil solarization is a chemical-free, relatively low-maintenance method of pest and weed control. Solarization harnesses the sun’s energy and makes chemical pesticides and herbicides unnecessary. And once the initial setup is complete, all that is required of the gardener is patience!

The main disadvantage of solarization is that while the increased soil temperatures will kill harmful insects and organisms, they may also eliminate those good for the soil. However, while the unwanted organisms stay away for up to four months, the beneficial ones will return much more quickly.

The Process

To solarize your soil, you’ll need clear plastic that’s at least 1.5mm thick and a little larger than the targeted area. Follow these steps to prepare the site and apply and seal the plastic:

  • Clear the site of all plants, weeds, and debris.
  • Wet the soil. 
  • Till the top six inches of the area (this encourages heat penetration).
  • Rake the site and check that the center is raised (to prevent water from puddling on the plastic).
  • Stretch the sturdy plastic over the area.
  • Weigh down the edges of the plastic with earth to completely seal the cover.

Troubleshooting

Weeds growing underneath the plastic is a sign that something is not correct. Check for loose edges and rebury them. If you notice any holes in the plastic, seal them with small pieces of duct tape.

Timing Matters

Soil solarization, reliant on heat, should be done during the hottest months of the year: June, July, and August. It is most effective under these conditions:

  • Moist soil at the start. Moisture will aid in the heat conduction process, so it’s best to apply and secure your plastic the day after watering or rain. Starting with either very dry or very wet soil will not give you the results you need.
  • Full sun. Remember, this method relies on sunlight to conduct heat to the soil, so shade from buildings or trees will impact the process.
  • Adequate time covered. Keep the soil covered for at least six weeks to ensure that pests and weeds are indeed eliminated before you begin planting.

Our thanks to University of Florida IFAS Gardening Solutions for helpful information on this topic.

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