If you want to make your own potting soil from compost, you should steam the soil before use. This largely removes weed seeds and pathogens, as well as unwanted pests in the soil.

Small amounts of potting soil can be sterilized in the pressure cooker

Make your own potting soil

Potting soil can be made by yourself if a compost bin is available. The compost contains plenty of water, few nutrients and the pH value is acceptable, in principle just the right composition.
Since there is usually no “hot rotting” in the conventional compost box, i.e. temperatures between 60 and 80 degrees are not reached, they remain in the ground

  • weed seeds
  • Larvae and eggs of soil pests
  • unwanted bacteria and viruses
  • fungal spores
  • nematodes

Why steam earth?

When steaming the earth, hot steam is used. This successfully kills germs, fungi, etc. However, only as much soil should be sterilized as is currently needed.

steaming temperatures

Depending on which pests are to be controlled, the steaming temperature and time will change. Viruses, for example, are dead at around 90 degrees, and fungal spores lose their ability to germinate at 70 degrees. Insect eggs and larvae do not survive 55 degrees. So half an hour of steaming at 90 degrees should remove most of the pests etc.

Three sterilization options

Potting soil can be sterilized in a number of ways.

In the oven

The oven is well suited for the sterilization of potting soil.

  1. Preheat the oven to 100 degrees.
  2. Take a deep baking tray and line it with parchment paper…
  3. Spread the earth on it.
  4. Moisten the soil a little.
  5. Cover everything with aluminum foil.
  6. Steam the earth for 30 minutes.
  7. Let them cool down well before use.

If you do not use the soil immediately, seal it airtight in a bag. So no new germs can penetrate.

In the microwave

Here you can sterilize small amounts of soil in a short time. The moist soil is heated in the microwave vessel for 10 minutes at 600 watts.

In the pressure cooker

Earth in flat bowls (preferably grill bowls), covered with aluminum foil, is placed in the steamer attachment of the saucepan. Now water comes into the pot, then the steamer attachment. The pot is closed with the lid. When the water boils, the valve can be closed so that pressure is created. The earth is steamed for 15 minutes.
After it has completely cooled down, the pot can be opened.

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Care tips