Soil Blocks: the Building Blocks of Life

Within the first few days of seed germination the maximum yield for your vegetable plant has already been determined. From that point on any and all types of stress that the plant sustains has a direct impact upon your harvest, be it from the weather, nutrients, water, chickens, children, insects, cloudy days, etc. Thus any effort you make to increase your yield in reality is an effort made to decrease your loss of yield. As garden manager, your role then is to identify ways to reduce plant stress at every possible stage to ensure a bounteous crop of nutrient rich food.

blockerThe place to start your plant stress reduction strategies is during seeding, actually it starts with seed selection but that’s for another time. I quickly learned during my first year of indoor seed starting that there was a trick to accomplishing this successfully. First, it didn’t take me long to realized that I was going to have to replace all my black plastic seedling flats every single year, they sure make those things cheap. It also just pains me to have to buy the same thing over and over again year after year, but what other options were available? A little bit of online research revealed to me another method and no more plastic cells and pots. Instead, the pot can be made of the soil itself, soil blocks!

With soil blocks, my young plants grew more vigorously and were highly resistant to the stress of transplant shock. Also, the seedling roots no longer spiraled out of control at the bottom of the cell or pot, but instead upon hitting the outside air the roots will check their own growth and then shoot off again after transplanting. Additionally, losses due to transplant shock were very rare with almost 100% transplant success. There are however a few new concerns. First, you have to be more careful with watering, the extra soil surface area dry’s out a little faster, but that’s easily managed. The other thing is that it’s more time consuming to build the blocks, but this is one area you can have a big impact on plant stress and its worth the extra time, besides its still winter and it gives me something enjoyable to do.

If you want to try soil blocks here is my method, there are many variations so don’t think this is the only way:

  1. soilblocksPick up the soil blocker of your choice off the internet, you can even find directions for making your own. I purchased a 4-cell two inch block maker and it will last me a lifetime of use.
  2. Pick up several higher quality leak proof seedling flats, still black plastic but reusable every year. Naturally they cost a little more, but the price makes up for itself after only one year. Whatever trays you use its important that they do not leak. All the trays I bought from the big box store’s were junk.
  3. Pick up an equal number of black plastic flats that are perforated, or just melt some extra holes into the ones you were going to throw away from last year. The flats I found at my local seed store were exactly that.
  4. Insert the perforated flat into the leek proof flat. When you want to water your blocks gently pull the top tray out, add water to the bottom tray and reinsert the top tray. Always bottom water your soil blocks.
  5. Make your block mixture. There is a trick to this, if you use the wrong materials, not enough water, or too much water then your blocks may not work out. I use about 80% soil less seed starting mixture, 10% high quality worm castings, 5% rock dust, 5% kelp meal and a bacteria/fungal biological inoculation. Mix with water to the right consistency and start making your blocks.
  6. Space the blocks on your trays so there is at least a 1/2 inch of space between them.
  7. Drop your seed of choice into the small hole at the top. Then for most seeds I take a pinch of the soil less mixture and cover the seed, followed with a squirt from the spray bottle to dampen it.
  8. Cover with a clear plastic dome to create a moist environment and wait for germination.
  9. Drink a nice glass of wine to celebrate your hard work and reduce your own stress.


6 thoughts on “Soil Blocks: the Building Blocks of Life

  1. What website did you use to purchase your soil block form and what is the name of the inoculant? I have a worm compost bin. Do you think I can use the really soupy stuff that is in the bottom level? I don’t want to have seeds germinate from the compost like they do when I put it in my beds.

  2. Hi Julie,

    I think at the time I had to order it from somewhere in England, but I did notice that Johnny’s Seeds carries them now. I think it was about $25. Right now I use two biological inoculants, both are from Tainio Technology (a local biological farming company), the first is fungally dominated and its called MycoGeneses, the second is bacterially dominated called BioGenesis. There are many other vendors that sell similar products, so they are not the only ones. Its also interesting to note that many premium organic fertilizers at the local gardening stores now also contain biological inoculants. In the future I will do a detailed posting on what these do.

  3. I pretty much mimicked your shelf and light setup. I wish I would have got rack type shelves, mine are wood. Where did you get yours ? My soil mix is about 50/50 potting soil and compost that i made from garden and ktichen waste, will let you know how it works out. I like your mix and think the inoculations enhance success, and if I consider the work and expense of this setup it may have been a logical extension, oh well, always next year if it crashes. My mix is not sterile, so could have damping off and other fungal/bacteria problems. How much water do you have showing in the bottom of your tray that contains the soil blocks ? Do the blocks seem saturated throughout the germination and growth phases ? You keep them covered until they germinate ? I do not have covers for my flats, so will just have to go topless. Thank you for your posts, lots of helpful information here. Kevin

    • Hi Kevin,
      I got the shelving from a big box store. I checked a couple different stores to see who was the cheapest and they all had them in silver, white and black. For germination I use clear plastic lids, without those you just need to keep it moist using a spray bottle. I remove them once I am happy with the germination. I like to keep the blocks moist and add water if the top half of the block seems dry.

  4. Pingback: Planting Soil Blocks | Blaming Nature

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