This is a fascinating bit of research into vermicompost and tomato seed germination rates of tomato (and lettuce seeds) (and subsequent growth) when the seeds were soaked for 24 hours in vermicompost water extracts.
The concentrations of the extracts used were 10%, 5%, 3%, 1% (1:10, 1:20, 1:33, and 1:100 vermicompost-to-water ratio by volume), and 0% (water control).
Seeds were soaked for 9 hours.
Germination rates improved significantly over water for all concentrations and the higher the concentration the better the germination and subsequent growth. (Doug notes – you want to be careful here, just because the authors found greater differences as concentrations increased, this may or may not work out in practice. I intend to mess about with some of the lower to intermediate amounts and only experiment with higher ranges. In other words, don’t put all your crop into a higher range with no backup plan)
Seeds were also tested on length of time of soaking with the range between 1 and 24 hours. Again, results indicated the 24 hour range significantly improved germination and subsequent growth.
BUT – the longer the time germinated – and the higher the concentration didn’t necessarily produce the best growth and germination rates together. In other words, some seeds germinated better but that didn’t mean they grew better. And some seed lots didn’t germinate better but grew better. There is some “interaction” between the growth hormones etc that isn’t understood.
From a practical point of view then – use a mid-range concentration to for 12 hours or so (start soaking in morning and sow into soilless mix in the evening) and you’ll get the best results.
From HortScience: 1 December 2012; Vol. 47, No. 12