Preservatives to prevent mold growth?

[Shane]

I was wondering if anyone's added preservatives to soil or has opinions about it. Despite heating to soil 180 F and sterilizing everything, mold still grew in about half my containers. I'm thinking there has to be a better way...

After some research, I think potassium sorbate and sodium benzoate are good candidates. I did some research and found k-sorbate has existing agricultural applications. It's currently used in combination with fungicides and also may be used as a seed preservative (it's been suggested but I can't tell if it's been used or not). Both should be easy to get, particularly stateside where k-sorbate is sold as a homebrew additive. At a 0.1% concentration, a pound of either would treat half a ton of soil(!)

The two things I'm worried about are
1) degradation/loss of effectiveness over time
2) adverse effects on seedlings (probably unlikely?)

Has anyone done or heard of this?

[supergodzilla]

Never heard of it, seems unnecessary, but I'm all for experimentation.

Even so, it feels like there would be easier conventional methods to dealing with mould. I just nuke my soil for five minutes in the microwave and bag it up and everything is rosy. The only mould outbreaks come from the seed coats themselves, which is why I soak everything in half-strength bleach for thirty minutes before sowing.

[Shane]

Mold could be one of those issues that disappears as I become more experienced. I should also note I haven't sterilized my seeds in the past. Also I'm all for continuing to sterilize everything, I'm just thinking about this as an additional step. I transplanted seedlings from sand to soil and the soil molded, that's what really got me. I can't even blame the (not present) seeds for that...

I soak everything in half-strength bleach for thirty minutes before sowing

Like half bleach straight out of the bottle and half water? That seems really strong

[Jangaudi]

I cover the top layer of soil with small stones (depending on the size of the seeds) which is a technique I read on this forum somewhere. I drop the seeds in between them so they touch the wet soil. Once germination is finished, I open the lid of the container once a while, shaking off the condensation, so the humidity is lowered considerably over time, but keeping it humid enough for growth. Works pretty well. I also did try the cinnamon concept, but I can't really figure out if it makes any difference.

[Jangaudi]

oh, and yes, diluted bleach for the seeds, and microwaving the soil as well.

[supergodzilla]

Like half bleach straight out of the bottle and half water? That seems really strong

Yeah, that's right. Never had any problems, has no impact on germination and never end up with mouldy seeds.

[Glorioustache]

Try watering them with a 1% hydrogen peroxide solution. Effective. It also kills beneficial bacteria in the soil, so keep that in mind.