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Need advice for a seed starting mix

Posted by mommymammal z5NY (My Page) on
Sat, Feb 26, 11 at 11:50

Cornell University studied a variety of seed starting mixes that they concocted with many different soil amendments--their control was a commercially available product. The mixes they made with hog or dairy manure-based vermicompost tended to do especially well; adding dried blood improved performance even more. The #1 best-performing mixture was made with 90% peat mix (peat, vermiculite, and perlite), 10% dairy vermicompost, and added dried blood, rock phosphate, and greensand. All of those ingredients are readily available, and in fact I have most of them. My question concerns the amounts of the latter 3 ingredients. Cornell's study talked about pounds per cubic yard of soil. I'm planning to start on a much, much smaller scale--I basically need measurements in cups and teaspoons! Any suggestions about proportions of these soil amendments?


Follow-Up Postings:

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RE: Need advice for a seed starting mix

Can you tell us what seeds were being used in the Cornell tests? I do not use the same mix for all seeds and would be interested in the choice for their tests. Al


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RE: Need advice for a seed starting mix

They used tomatoes--a variety called "Mt. Fresh." The article was published by the Cornell Dept. of Horticulture and called "Organic Transplant Media and Tomato Performance 2007." I'm planning to start mostly tomato and pepper seedlings, so this should be OK.


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RE: Need advice for a seed starting mix

Tomatoes and peppers will jump out of the ground with any mix you choose. Peppers however like a really warm soil for best germination, I start them at 85 degrees. Al


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RE: Need advice for a seed starting mix

Still...humor me. Anybody have a recipe for those soil amendments in small units, like tsp. or tbsp. sizes? I know it's not an exact science, but I need a rough idea of how to proceed. Any help would be appreciated.


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RE: Need advice for a seed starting mix

I do not use any fertilizer in seed starting mixes. Until seedlings have roots they can not use fertilizer. I am more concerned with the mix remaining moist and still containing enough air to drain. For those plants that are sure fire like tomato and pepper, ALMOST any bagged mix of your preference will work fine. I use a commercial mix I buy by the yard from a local landscape supply because I prefer a mix that will not break down in at least a year. Every nursery in the area uses the same for their own growing, though they do not resell it. I grow a lot of difficult to start plants, for which,I mix special mixes. Some seeds may take six months to germinate. You seem to be intent on making seed growing more difficult than necessary. Al


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RE: Need advice for a seed starting mix

And you seem intent on trying to make me feel guilty for wanting to try something different! I'm not a newbie gardener--I've been at this for the better part of 40 years. One of the things I like about gardening, and appreciate about gardeners, is the opportunity for and willingness to engage in experimentation. There are endless ways to reinvent the mousetrap, as it were, and that's what keeps things fun. Seriously, though, I do appreciate your input--that's what the forum is for.


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RE: Need advice for a seed starting mix

I have no intent to limit your experimenting! In my lifetime of gardening, at 82 I have done a lot of experimenting, most by my not KNOWING it was an experiment. At this time I am looking for what works, with less of MY work. I am glad you were not really offended by my snappishness. Al


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RE: Need advice for a seed starting mix

I don't think fertilizer really comes into play until after the seedlings reach the 2nd set of true leaves phase, it generally uses the stored resources in the cotyledon. As Calistoga said, other considerations such as moisture, drainage, light and temp seem far more important than available nutrients, until the seedling roots start spreading.

Dried blood, fish emulsion and other organic N sources seem almost useless in a sterile potting mix, the N often doesn't become available until acted on by soil microbes, which are by definition largely absent in sterile mixes. Using compost or manure or vermicompost avoids this issue, but provides a non-sterile medium that can possibly increase pathogens such as damping-off.

I cant understand why anyone would need P or K from greensand or rock phosphate, unless they are growing the plant to maturity in that container. Ca or Fe would be more useful, imo, but again only after the roots are searching for nutrients. But I'm not an expert, that's just my understanding of the germination process, so I don't mind if I get schooled on any incorrect info.


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RE: Need advice for a seed starting mix

Several things (a) I will be leaving the plants in the mix until they have several sets of leaves and well developed roots (growing the seedlings inside of jumbo eggshells, and transplanting them shell and all) so they WILL need some fertilizer. Yes, I know they need light and moisture and aeration and all that, too. (b) The microbes in the vermicompost protect against damping off; that's why I want to try the mix. I've had problems with damping off before, even when using sterile mix (as nothing STAYS sterile...) (c) while a simple 9:1 mix of seed starter mix:vermicompost is adequate, the study by Cornell that I was referencing demonstrated even better results when bloodmeal was added to any mixture containing vermicompost--not as a fertilizer for the seedlings, but rather as a potentiator for the beneficial microbes in the vermicompost! Ergo my desire to give their mixture a try. (c) Now, I don't know how important the greensand and rock phosphate are to the success, but they were ingredients in Cornell's top-performing mixture. I can probably fake it; as I said before, it's a question of units, and I'm working on a much smaller scale than Cornell's pounds and cubic yards...
And before anyone tries to give me a hard time about the eggshells, they work fantastically well! No transplant shock at all! Last year, my little egg-grown tomato seedlings outgrew and outperformed store-bought transplants in 4" pots that were several times their size when I planted them in the garden. Going to do it again this year.


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RE: Need advice for a seed starting mix

could you find a converter online to switch all of your measurements to ounces and then divide by 200 (or another number to reach your volume goal)?

Just a thought

Keriann~


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RE: Need advice for a seed starting mix

I'm with Keriann. I think probably you'll need to do the math and find an online volume converter. Alternatively, you could try contacting Cornell directly and just ask them. It doesn't hurt to ask. I do it all the time! The worst that can happen is that they either ignore you or say "sorry can't help." At least you tried though and you might get the exact measurement. ;)


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