I stumbled upon soil blocks recently. As a concept it's perfect. In reality I'm not sure. I haven't read everything on permies, but a lot, and just scratched the surface on the internet in general. I have spent quite a few hours reading and watching info on soil blocks.
I decided to give it a try. I bought a 3/4" soil block maker thinking I can start lots of seeds on the heat mat, with the benefit of up planting as soon as the seedling emerge from the soil, instead of having some fast germinating seeds get leggy waiting for the slower ones. Also it makes 20 blocks at a time. I did experiment with my soil mixture using shredded cardboard instead of peat or coco coir, and it worked well. I made my own larger soil block maker. I was going for 2"X2", but it ended up 3"X3". It worked, but needs modifications to make it easier to use. I found some coco coir and peat moss ( not buying it anymore, but might as well use it), so I went ahead and used it. I also added some bone meal, and organic fertilizer to the mix since I figure it will be in it for a while.
1st blocks held together very well, some roots stick through the bottom, so must not be to dense. It was easy to replant as needed leaving the others. The down side was it was only good for small seeds, medium and large seeds don't work. Some seeds sprouted on top so I can see root and seedling. I wish I would have brought the 2" block maker.
2nd up potting was super easy, just pop it into place. I made the block so it made a 3/4" depression. I sprinkled mycorrhiza in the hole, and popped the seedling in. Sprinkled a little vermiculite to fill any gaps. Very quick and easy. What I don't like is my blocks are to big and have only one seedling it takes up to much room. I only made 12 of my larger blocks. The rest of the seedlings I used a good organic potting soil in plastic pots I had. Each pot got 3 or 4 seedlings. I decided if I change the tray under the lg. Blocks I might be able to get more in, because I still have seedlings that need to be up potted. When I tried to move them they started to fall apart, so I must not have gotten the mix right. I'm still going to do it because I need the space. I will just be careful, and squeeze it back together.
I started 17 kinds of seeds. I made 12 blocks. I made sure each block had a different kind of seedling in it so I could compare the difference.
I expected the single seedling lg. Soil blocks to out preform the plastic pots. At this early stage that is not the case. They all look healthy, but some in the pots have there first true leaves, and the soil block ones don't.
It's early yet, and it's always tough to learn a new skill, but so far I'm not sure soil blocks are worth the effort. The main benefit of soil blocks is not getting root bound, no transplant shock, and no plastic. Seems like if I start the seeds at the right time, so I can plant them outside before they become root bound then it isn't a problem. I would still like to eliminate plastic, but I have lots of plastic pots and cups that still have years of use in them. Well time will tell.
I'm interested in hearing what you all think. From what I've read it seems people love soil blocks, or hate them. Thanks