Sunday, February 14, 2010
Why Sterilize Soil Before Sowing Seeds?
What better way to anticipate the coming spring amidst all this cold weather than to plan your vegetable garden. With that in mind, as you collect your supplies and get ready to plant your seeds, consider this. If you ever wondered why agricultural extension folks suggest sterilizing your soil before starting seeds for your vegetable garden, this picture might be worth all those words you didn't read. Each of the four small compartments received 10 clover seeds on February 3rd. As you can see, the two compartments on the left held soil that had been sterilized, in this case meaning the soil was heated to 200 degrees F for 20 minutes in a microwave oven in my kitchen. Two days later seeds were germinating in all compartments.
It is worth noting that I set up this little test to see if the sterilization process released any toxins into the soil that might inhibit seed germination, as that is one danger of heating soil to 200 degrees. So when the seeds in the sterilized soil germinated as readily as those in the untreated soil, I felt confident that I could use the sterilized soil to start the seeds for this coming spring's vegetable garden.
As the seeds came up, I continued to keep track of how many successfully germinated in both sterilized and unsterilized soil. Here are some of the results:
3 DAYS: STERILIZED - 17; UNSTERILIZED - 15
4 DAYS: STERILIZED - 18; UNSTERILIZED - 19
6 DAYS: STERILIZED - 18; UNSTERILIZED - 19
Yesterday, day 10, I first noticed that a couple of the seedlings in the unsterilized soil collapsed. Today, day 11, I took the picture above. Fungus is more than likely responsible, fungus that heating to 200 degrees F killed. In this case the fungus did not inhibit seed germination, but did kill several of the very young seedlings.