Hi all, I attempted to sterilize soil in my electric oven but in some cases the soil went beyond 210F for maybe 10-20 mins... and I've heard that overheating soil during the sterilization process produces plant toxins, or breaks down the soil, unleashes ammonia etc. The ideal temperature for sterilization is said to be 180F but can the threshold be lower than than to avoid potentially damaging the soil by going over 190-200F? Also, is it better to sterilize perlite (if it is contaminated) or even sand separately using water? Happy grows, all.
Your kidding? Electric oven? Why? Are you just having fun with the oven or is this for a biology project? Compost kills anything bad at approx 165. This is compost. As for soil. You don't use the oven. Please start by explaining your needs and setbacks.
I had to try sterilize wet soil/sand (in this case it is a premium seed starting mix) because sometimes I would crack open the unsprouted seeds from my previous attempts to investigate what was going wrong, and would promptly see gross critters roaring around inside the now dead seed husk, and this was from sealed, store brought mixes. I think sterilizing is more important to germinate seeds rather than transplanting plants you have grown, especially if your seeds cost $$$ or is few in numbers. My seeds (Morning glory and Hawaiian baby woodrose) germinated in soil that I had 'sterlized' so I didn't notice any bad effects like terminated germination, etc, from toxins(?) generated by accidentally heating wet soil a bit beyond 200F, at this point in time, but I wouldn't do it again, to go beyond 200F. As it seems like 165F is quite enough to sterilize the soil of its seed eating nasties, I do not need to keep it 180F for 30 solid minutes like some sites suggest, but rather let it go up to 180F then turn off the oven so the temperature rides down. I don't heat the perlite with the soil/sand as the pertile should be kept clean until the final mix. I think heat degrades perlite. I still need to do a sterilized/ unsterilized germination test, because otherwise it might be the quality of the growing mix itself.
