Virtually all of the nutrients will still be there. No worries. I'd use a microwave oven.

microwave seems like a better idea. quick zap for a min or two. thanks.

FWIW, I routinely sterilize my seedling mixes, and never have any problems with damping off.

If I were you I'd use a thermometer to probe the mix. In a microwave oven in particular, the mix can get non-uniformly heated. More heat is better. You won't lose any quality.

How long you nuke it for depends entirely on how much there is. A minute or two won't sterilize a cup of material. If you're going to do it, do it right.

Good point about dampening. Microwaving won't heat dry soil. Period. On second thought, a minute or two might do the trick for a cup of soil. What counts is not how much soil is in the cup, but how much water is in the soil in that cup.

well my microwave blew up..
just kidding.

decided i didn't want to go through the extra step so picked up some miracle gro nature's care organic mix, link. to my surprise, it has some pretty nice ingredients. Kelp, Alfalfa meal, bone meal and earthworm castings. base is perlite, coir, peat, yucca, forest hummus.

i think Miracle gro is probably a bit better known brand and perhaps they go through some extra steps so there is less chance of bugs, so i'll take my chances.. the reviews are great.

I don't worry about sterlizing soil. I do take seedlings outside where they get good ventilation and I do not have damping off or such.

Whatever you do, don't ever put soil or potting mix into the oven to bake. Soil in particular will stink up your entire house in a way you could not possibly imagine until you've experienced it.

I like the steam/microwave approach, if you must. I suspect a clear plastic bag, out in the sun on a hot day, would do pretty much the same thing? It may not reach 200F but a longer duration might make up for it. Might work for larger amounts.

I have used the microwave with water as lazy_gardens suggests above. My undergraduate major was medical microbiology and the microwave seems like a reasonable solution for 'sterilizing' soil.

I have an outdoor oven that I sterilize my planting mixes with. Doesn't really stink, but hey, it's outside, so who cares? Do not bake at high temp. If you bake at 350-400F, you'll start browning the organics and carbonize a lot of them. Now, that could stink. 250F for an hour works fine.

Steam sterilization is a carefully defined process. 250F at pressure for 15 minutes kills everything. A bit longer if you don't have pressure should work well. Spores can survive 212F.

250F at pressure for 15 minutes kills everything. A bit longer if you
don't have pressure should work well. Spores can survive 212F.

Maybe a use for the instant pot?

I used to do environmental fate studies on chemicals and we had to have a 'sterile' soil control to verify whether the degradation of the test chemical was actually biological in nature. We could never get a soil to stay sterile. Usually we autoclaved them (steam+pressure for those who aren't familiar), let it sit for a day or two and autoclave it again. Still, after a few days there were always thousands of microbes. But at least there weren't millions so it was 'good enough' for our purposes. In any case I learned that really sterilizing soil is virtually impossible, short of burning it, which defeats the purpose. This isn't really a problem as far as seed sprouting - you just want to knock down the population and give the seedlings a chance to get their legs under them.