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I think the idea of soil blocks is great, particularly in its cost effectiveness. However, they are the most tedious things to make on the planet, and they require a special soil mix and special care to ensure that they stay together. Our ¾ inch soil maker pops out about 20 blocks at a time. After we made enough to plant this summer's supply of shallots in, we still had to plant 4 seeds into each tiny block. We left our tiny blocks in our mist room in the green house to sprout.
Several weeks later, we had to transplant the tiny blocks to the next size up of a 2 inch block. Now this was the kick in the pants of the soil blocks--since they had been sitting too wet in the mist house, the blocks had become super-saturated and weren't holding together well. Additionally, since the shallots had sprouted and were full of nice, healthy roots they had torn apart the ¼ inch blocks. Basically, there was no structure left to them. Somehow, we had to smoosh together some form of a soil block and place them on top of the 2 inch blocks. Ultimately we were lucky to salvage any of our shallot starts after the mishap.
Again, I like the soil blocks. For organic farms they are great, and offer some real advantages. But be prepared for some challenges.