I've been experimenting with various potting soils, purchased top soils, seeding mediums, and good old homegrown compost to see which does the best job for starting seedlings. I started 3 trays with 1 being straight store bought topsoil, 1 tray 1/2 topsoil and 1/2 homemade compost, and the final tray pure homegrown goodness. Two weeks into growing this was the result:
Pure compost is on the far right. Huh. Take a good look at the tomatoes in the second photo, same seeding date. For the next seeding of tomatoes I started them in seed starting medium and once their true leaves appeared transplanted them into trays filled with 1/2 compost and 1/2 a different bagged soil. They are doing quite well, but no where near as well as the ones planted in the pure compost.
The results are even more apparent now a month later. The seeds started in the bagged topsoil have just stalled out completely. Thankfully these were the seeds I only grew for the trial, not the tomatoes I'm relying on for growing seeds ~ WHEW!
This has lead to lots of reading and research as you can imagine. It is VERY interesting, anything published lately that talks about starting seeds and 'making your own seed starting mix' all rely on purchased materials. Perlite, vermiculite, peat, blah blah blah. Even the most 'self-sufficient' focused books lead you to believe this is the path to take. Take a bag of this and a bag of that and mix them. Not locally produced to say the least!
Then I read Helen Nearing's book about their greenhouse back in the day. Her recipe for seed flat soil mixture??? Here it is .... Equal parts of sand, compost, rotted sod, garden soil and wood dirt (forest humus). This with a sprinkling of a nutrient mixture of soybean meal (or cottonseed or seaweed) phosphate rock powder, granite dust or dolomite lime. Her seed flats were wood trays they built themselves and lined with sphagnum moss. There were lots of photos of their extensive compost bins in their book!
I was talking to a friend while touring her greenhouse of how I preferred to read self sufficiency books and articles from the '70's as those being written now seems so superficial and dependent on purchasing instead of truly making your own.
So remember .... these are your seeds on store bought (left)
And these are your seeds on homemade (right)
And, yes, they were seeded on the same day and treated the same way, well until the compost-planted seeds needed to be transplanted into larger pots that is!