Seed Starting Mix

brianj555 1/18/2018, 8:15 pm

I like to save money. So I had a go at making my own seed starting Mix for tomatoes. I read an article (only one , probably a mistake) that referred to tomatoes being considered heavy feeders (as far as seeds are concerned) and the recipe basically called for sterilized Mel’s mix. I thought to myself, I said “self... I have all that stuff , let’s make some. “ so I made a bunch

. I read to bake it at 150 Celsius (305 F) for 45 minutes, which I did. After making all this stuff up, I read more articles that said if the temp gets too high , that’s really bad. It said to use a thermometer and to make sure the internal temp didn’t exceed 140. Before 140 the mix is not sterile and contains disease. Higher than 140 it starts to kill good stuff which makes disease spread even faster than non sterilized. The article I read never mentioned using a thermometer at all so I have no idea what temp the mix got up to. I’ve only used a little so far, but I would really hate to throw the rest out unless you guys think I should. What do y’all think??

SQWIB 1/18/2018, 8:36 pm

I have sterilized potting soil to reuse in desperation once.
From what I remember is you want to take it to no more than 200 . And for 30 minutes
You need time more than heat to sterilize.
IIRC too high of a heat creates toxins

**trolleydriver** 1/18/2018, 8:39 pm

I've used new Mel's Mix for seed starting. Never sterilized it.

SQWIB 1/18/2018, 9:02 pm

And seeds aren't heavy feeders, the plants are.
The seed contains everything it needs to sprout.

brianj555 1/19/2018, 10:17 am

SQWIB wrote:I have sterilized potting soil to reuse in desperation once.
From what I remember is you want to take it to no more than 200 . And for 30 minutes
You need time more than heat to sterilize.
IIRC too high of a heat creates toxins

Yeah. That’s what I read too. But what toxins??? I can’t find that info.

SQWIB 1/19/2018, 11:21 am

brianj555 wrote:
SQWIB wrote:I have sterilized potting soil to reuse in desperation once.
From what I remember is you want to take it to no more than 200 . And for 30 minutes
You need time more than heat to sterilize.
IIRC too high of a heat creates toxins
Yeah. That’s what I read too. But what toxins??? I can’t find that info.

I would just buy potting soil and not worry about all this stuff...
However,
This is just regurgitated information from a website.

Heating soil or nursery mix to excessively high temperatures will use more energy than is required and can have adverse affects on beneficial microorganisms. Excessive soil heating may also increase chance of phytotoxicity due to soluble salts, manganese toxicity, and toxic organic compounds. It is safe to treat a UC type soil mix (fine sand and sphagnum peat moss or hypnum peat moss) to a temperature of 212F (100C) without developing soil toxicity to plants. Soil mixtures high in readily decomposable organic matter (manure, leaf mold, compost) are most likely to give injury when exposed to excessively high temperatures (Baker 1957 p129). Note that composting facilities, depending on their size, are subject to regulations concerning minimum temperatures and duration LINK.

Here is the website

brianj555 1/19/2018, 11:30 am

SQWIB wrote:
brianj555 wrote:
SQWIB wrote:I have sterilized potting soil to reuse in desperation once.
From what I remember is you want to take it to no more than 200 . And for 30 minutes
You need time more than heat to sterilize.
IIRC too high of a heat creates toxins
Yeah. That’s what I read too. But what toxins??? I can’t find that info.

I would just buy potting soil and not worry about all this stuff...
However,
This is just regurgitated information from a website.

Heating soil or nursery mix to excessively high temperatures will use more energy than is required and can have adverse affects on beneficial microorganisms. Excessive soil heating may also increase chance of phytotoxicity due to soluble salts, manganese toxicity, and toxic organic compounds. It is safe to treat a UC type soil mix (fine sand and sphagnum peat moss or hypnum peat moss) to a temperature of 212F (100C) without developing soil toxicity to plants. Soil mixtures high in readily decomposable organic matter (manure, leaf mold, compost) are most likely to give injury when exposed to excessively high temperatures (Baker 1957 p129). Note that composting facilities, depending on their size, are subject to regulations concerning minimum temperatures and duration LINK.

Here is the website

Thanks Sqwib. I’m making a new batch now and only sterilizing the compost. It’s a mixture of stuff bought from the feed and seed near me. Mushroom, black kow and chicken. I’m just doing it at 200 until it reaches 180. Do you think there is any need or reason to sterilize the vermiculite or peat?

**trolleydriver** 1/19/2018, 11:42 am

Brian, I think you are over thinking this and making it more difficult for yourself. If you have concerns just buy potting mix.

SQWIB 1/19/2018, 3:28 pm

I wouldn't bother with any of it, the only time I ever sterilized (potting) soil was I needed some for some micro greens and couldn't run out to the store at the moment.

Peat and vermiculite are inert

brianj555 1/19/2018, 9:14 pm

SQWIB wrote:I wouldn't bother with any of it, the only time I ever sterilized (potting) soil was I needed some for some micro greens and couldn't run out to the store at the moment.

Peat and vermiculite are inert

Thanks Sqwib.

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