I am thinking about producing my own potting mix. The problem is that most recepies involve:
a) Using non renewable resources (peat, vermiculit),
b) Non local resources (coconut)
c) Using an oven to sterilize the mix (not cost efficient).
I know the biointensive farmers use a simple mix of 1 to 1 compost and soil to start seeds in frames. But I am concerned about the potential pathogens in unsterilized soil and compost. The other method I found is using a solar cooker to bake the soil but I do not live in a hot climate.
Any good ideas for a mix to start seeds that would use resources generated on site in a cost effective way?
you want a not overly hot soil and a good texture for young roots to take hold in. maybe some strained compost from your site mixed with sand. I would go for a 50/50 mix. If you think your compost is to hot you could put it in a pot with drainage holes and wateralot, that way you leak the nutrients out of the compost, but for most vegetables and herbs I think you are fine. I wouldn't use compost with alot of manure since it could be too hot.
You know, the sterilisation thing might be exaggerated. I think if you use a healthy soil mixed with healthy finished compost, the soil ecosystem might actually be safer for your seeds than trying to sterilise. I've always used random garden soil and haven't often had problems with germinated seeds dying off. If you use nice natural forest soil or the best mix you can manage, it's likely to be fine. Just like antibiotics may cause a domino effect of other infections and disorders, and it's better to leave your guy microbiome intact, similarly the soil ecosystem might be perfectly nice and hospitable for seeds.
Works at a residential alternative high school in the Himalayas SECMOL.org . "Back home" is Cape Cod, E Coast USA.
A sterile medium will be colonized by the most opportunistic organisms. A medium that has a healthy soil food Web is already colonized and in good balance. It will not be easily taken over by opportunists.
I know which makes more sense to me.
What and how are you germinating? I find that seeds that take longer to germinate, or seeds that are germinated in a closed environment like a heated propagator- suffer worst from spores and things in the soil (as they're around longer for the pathogens to have an effect). Germinating in open containers, or fast-germinating seeds all seem to not mind living in plain old garden soil, but something like tomatillos or some chillis are best done in sterile soil as they take forever and the mould and things grow faster than they do.