How to Use Black Plastic to Sterilize Soil

While most plants, fruit and vegetable need fertilize, organic soil to sprout to their healthiest, some soil contains bacteria, fungi and weed seeds that can ruin a growing endeavor from the second you sow your seeds or transplant your sprouts. To kill weed seeds and harmful organisms without toxic chemicals, try a process called solarization, which uses the sun's natural heat to sterilize the soil, essentially cooking the unwanted material in the soil so that it can no longer bother your plants.

Soil tiller
Hose
Black plastic sheeting
Rocks or bricks
Compost or humus

Instructions

- 1
  Till the area of the garden you need to sterilize to a depth of 12 inches. This will bring weed seeds closer to the surface, better ensuring that they will be cooked during solarization.
- 2
  Water the soil deeply so that the top 12 inches are thoroughly moist. This will help with the heating process, as the water conducts heat deeper into the soil.
- 3
  Cover the entire area with thin black plastic sheeting. Hold down the edges of the sheeting with large rocks or bricks to ensure that it will not blow up and allow cooler air underneath. You must seal all edges completely for the solarization to work.
- 4
  Check the soil every two weeks to ensure that it is still moist; if necessary, lift the plastic briefly to moisten the soil again. Leave the plastic in place for at least six weeks, up to eight weeks if the temperatures are not steadily above 70 degrees F during the process.
- 5
  Remove the plastic and mix compost or humus into the soil before planting to freshen the fertility of the soil with healthy organisms.

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