Sunday, January 31, 2010

I Played With the Soil Block Maker!

If you google “soil block recipe” you will find there are many different recipes for soil block makers. The recipe Johnny’s sent me with the soil block maker I purchased is Eliot Coleman’s soil block recipe:

BLOCKING MIX RECIPE From The New Organic Grower, by Eliot Coleman

A standard 10-quart bucket is the unit of measurement for the bulk ingredients. A standard cup measure is used for the supplementary ingredients. This recipe makes approximately 2 bushels of mix. Follow the steps in the order given.

3 buckets brown peat (standard peat moss, use a premium grade)
1⁄2 cup lime. Mix ingredients together thoroughly.
2 buckets coarse sand or perlite
3 cups base fertilizer (equal part mix blood meal, colloidal phosphate, and greensand). Mix.
1 bucket garden soil
2 buckets well-decomposed compost. Mix ingredients together thoroughly.

Sourcing out these individual items this time of the year is difficult. I checked the ingredients of seed starting mix and found it was made from approximately 80% peat moss, 19% perlite, 1% lime, and a wetting agent. So by adding some compost and using some balanced fertilizer, I am hoping to be close enough to the original recipe. I would probably be ok with most potting mixes too if I screened out the larger pieces. They usually are made from composted forest products, peat moss, perlite, and fertilizer.

I gathered my materials on the workbench in the basement which will now be my seed starting area:

I’ve been saving plastic produce and bakery containers to use a mini humidity domes:

First I added some hot water to the seed starting mix and let it sit for a while so the peat could absorb the water:

Then I added a few handful of compost and mixed well until it seemed to be the consistency of wet cement:

Some water oozed out when I squeezed a clump of the mix together like the instructions describe:

I filled the soil block maker by first mounding the mix, then pushing the blocker into the mix firmly until it reached the bottom of the container. Then I twisted the soil block maker, lifted it up, and scrapped the excess soil level with the soil block maker:

Then I moved it to the container:

And squeezed out the blocks in a neat row of four 2x2 inch blocks:

Some turned out better than others, but any rejects were just plopped back into the mix:

Twelve blocks fit snuggly in these repurposed salad containers:

And eight in this one:

All stacked up and ready to seed:


  1. Very cool GM! It will be so easy to transplant those soil blocks. They look awesome.

  2. Wonderful ! They look perfect. Now I just GOT to have one.

  3. This was a very informative post. I love the idea of making soil blocks yourself.

  4. Isn't playing in the mud fun? I make my soil blocks at the kitchen sink, and have a great time making a big mess :-) I basically use two parts of a good (bagged) forest products compost to two parts peat, then toss in as much vermiculite as I can afford (I can only find small $$$ bags here). I have also used perlite, but I don't like it as well for the blocks, as it tends to be chunkier. I thought I was doing something good for my tomato plants last year, and watered them with half strength Miracle Grow for Tomatoes. Darned near killed them. This year I'll not fertilize them at all, or try to find something that doesn't stink to high fish emulsion!

  5. I love the square boxes. I looked through my recycles the other day and just wasn't finding much. Sigh. I'll be doing my blocks in large flats I think.

  6. What a great reuse of those plastic trays! They make perfect humidity domes for those soil blocks.

  7. All right GM you are on the right track, your going to love them. John

  8. They look great! Have you tested their mobility yet? How do you plan on storing the left over soil mix?

  9. Thank you everyone for your comments. Please know that I am totally winging it here and experimenting with the soil mix based on materials I can find right now. I am sure for best results you should follow the tested recipe.

    Ribbit: I think I am going to like this method. Right now I am going to let the soil blocks dry out a bit and see if they hold up to watering.

    Miss M: They are quite fun and pretty fast to use too. I am hoping the soil mixture holds its shape.

    Kimsworld: Welcome and thanks!

    Granny: It WAS fun to play in the mud. I have some time to experiment, so I will play around with the mix a bit, let it dry out a little, and re-water. I want to see how the blocks hold up before seeding them.

    I will be staying away from stinky composts and fish emulsion. Wouldn’t want to smell up the house. Thanks for the warning on the miracle grow being too strong for the seedlings. I’ll need to research that further.

    Daphne: I don’t have any flats right now and was trying to avoid purchasing them. I think I like the salad and bakery containers. I hoping it will be easier for me to keep different things separated and labeled.

    KitsapFG: I thought the plastic containers would be useful. Little did I know that the soil blocks would fit so perfectly in them.

    John: Thanks! I am letting them dry out some so I can re-water and see how they stand up. I already suspect that I should add more compost to the mix.

    Momma S: I am able to lift them and move them. I only mixed up a small amount of soil mix to play with the soil blocker. I ended up using all of this for three test trays. Hmm, not sure how I will store it, I haven’t thought that far ahead. I think I may mix up a batch each seeding time so I can saturate the peat mix with hot water and let it soak in as much as it can.

  10. Good for you! Those soil blocks are pretty tempting, and I may just have to do the same one of these days.

  11. I remember reading that part of the appeal was that seedlings would self-trim their roots because of the air circulating around them, which means slatted flats, I think.

    It's going to be an interesting experiment, I think.

  12. EG: I bet you will engineer your own soil block maker.

    Stefaneener: Yes, "air-pruning" is the term I came across in my research. The roots go to the edges of the block and stop.

  13. Oh, you know I will! It'll be the deluxe model, too!

  14. OH HOW COOL! I need to get my act together and get going on this! I love that your recycled those containers. Are you going to cover your seeds with a bit of soil after you sow or just leave them uncovered?

    I'm sure we both will become experts eventually!

  15. Hey Thomas! I am watching your blog carefully to see how you are progressing too. I will cover the seeds a bit with some peat, I think.

  16. The blocks look great, those containers were made to be recycled as seed trays!

  17. Kelly: I swear they WERE made to be seed trays. They are perfect!