Healthier plant roots
No plastic pots
Finicky soil mix
Fall apart ?
This is what I am finding, and Elliott Coleman makes it look very easy. I have no personal experience, so I'm wondering if anybody has tricks, tips, warnings, endorsements, soil mixes. Or is nobody using these.
Coleman's mix is
3 parts peat
3 parts compost
1 part pearlite
Plus minerals and fertilizer
The soil mix does need to be good. I am not one for buying lots of peat moss and such, but I did manage to make a decent on-farm soil block mix using sand, clay, and compost. I dont remember the exact ratios, but it isnt that difficult to get right. It should be more dense and sticky than you would think for potting soil, otherwise it does fall apart.
Thing is, you need a ton of this mix for your soil blocks. The main thing that I was using soil blocks for was tomatoes and peppers, using the 4" blocks. I ultimatley gave up on the soil blocks because if I raised my tomatoes in 50 cell trays, and then transfered to half gallon plastic pots, I could use nice mix in the flats, and then just garden soil in the big pots. This was much easier to deal with.
I never saw better growth in the soil blocks. In fact, I think the half gallon pots grow a better transplant. The plastic trays and pots are reusable for years if you put them stacked in a shed. It is much cheaper using the plastic containers because the mix is so much cheaper.
Just my experience, I still have the soil blockers (2 inch and 4 inch), but I havent used them in years. It works for Elliot, no doubt, but was a disappointment for me. Of course, YMMV.
As far as the peat is concerned (many people feel that this is not a renewable resource), I have been informed by people living in the peat-bog regions that those bogs are expanding each year. If we (or somebody else) don't 'consume' this product, the peat will overrun millions of acres, making it unsuitable for anything else.
Next, perlite. I hate that shit. It is so light, that every time you water, it floats up. Eventually, almost all of it ends up on the surface, where the wind just blows it away.
I much prefer to use soil flats. Nothing is wasted that way. If a seed doesn't germinate, you only lose the temporary use of 1 square inch of soil. With soil blocks, you need to put 2-3 seeds in each, and select for the healthiest one, clip the rest. One half, to two thirds of your seed is wasted.
It was always the watering that broke the top corners off my cubes.
Dustin Powers wrote:I didnt love my soil cube until I used them on a wicking watering mat. Cubes stopped falling apart, root growth in its hunt for water was stronger therefore holding the cubes together better, and I just used a mix of my garden soil and some light potting soil.
It was always the watering that broke the top corners off my cubes.
What were you using for a wicking mat under your soil blocks? I've been thinking about making my own out of some unbleached, natural wool fabric. There's a bunch of different synthetic wicking mats (a.ka. capillary mats) out there on the market but I like to use the most natural materials I can. So if anyone has other suggestions (other than newspaper, haha) I'd appreciate it.
I would not use much clay in a soil block, and if I did, I would not use sand. After all, rammed earth is a compressed mix of sand and clay.
I would like to find an on-site replacement for peat, but haven't had time to experiment yet. In regards to expense, using soil blocks greatly reduces the need to add compost to the soil, so they might use more materials than starter trays, but it is important to look at the complete cost of the system.
I used 10" x 20" plastic trays in which I can put 40 or 44 2-inch soil blocs. I do not need any other plastic cell pak (so less cleaning to do and less stuff to pile somewhere !)
It needs some practice to find a good mix. Many will work, but I usally use a mix of commercial mix inoculated with mycorrhizae, compost and coco coir. I found that coco coir is really helping to maintain the sturdiness of soil blocks, especially for big 4" blocks. The right amount of water in the mix is also critical so the block won't fall apart.
I do not know if seedlings are healthier with soil blocks than with regular trays/pots, but I know that they are very healthy. They are sturdy, easy to manipulate and easy to water (just pour water in the 10x20 trays). I have not seen any difficulty for the roots to grow in the soil blocks.
I tend to use less often 3/4 inch blocks as I feel that it is more work and germination rates are already high in 2" blocks. For tomatoes, I use the longest pin with 2" block and I put the seed in the hole. As the plant (and its main stem) grows, the stem inside the hole seems to make roots and the seedling is quite sturdy.
I have made them with peat and coco peat. Both have worked well, though I personally want to find a local solution because importing those materials just brings up the cost and emissions of what I grow. I have read about making a degraded leaf litter as a peat replacement, but haven't tried this yet.
Here's a similar thread with good suggestions: https://permies.com/t/7049/organic/Soil-Block-Makers-Eco-conscious
Now I'm thinking; what if in the Fall we laid out several inches of compost, and planted clover or some other such plant in it, along with an annual grass. Then, we would cut the "sod" up into blocks and put them under cover to dry out and die. Come spring, could we rehydrate these and use them as soil blocks?
If a little clover came back, that would not necessarily be a bad thing.
I used the soil mix recipe from Eliot Coleman's The New Organic Grower. In that mix he advocates using sharp sand, not perlite. I generally used what I had - not-sharp sand, some used seasoil, compost and peat moss. I added amendments such as rock dust, greensand, lime, and some organic dried seaweed stuff. It worked great. The blocks held to gather well, and everything grew very healthy and strong. Misting is definitely the way to go with the 3/4" blocks, and the first few days of the 2" blocks. But once the roots have infiltrated the blocks, regular light watering worked well; although, I can definitely see the advantages of using some sort of capillary mat to water, as you would not have to be quite as diligent in keeping them watered.
All in all I was very pleased with the results. I think that experimenting with things like worm castings and leaf mould will be in order in the future. Anything that is nutrient rich, holds water, and holds together well should work brilliantly. I'd definitely like to be using only on-site materials as soon as possible. So, hopefully in the spring I'll have everything I need - compost, sand, garden soil, worm castings, leaf mould - and I'll have a go at using different mixes to see what works best.
Oh, how I love experimenting!!
I would avoid Peat moss for a multitude of reasons. My primary concern is it just doesn't absorb and distribute water properly, therefore requiring a host of other ingredients to compensate (perlite, vermiculite, etc). Even with perlite, the Peat blocks I made tended to dry out and harden readily. I switched to coco peat with vermicompost, which worked much better than the Peat moss. The vermicompost held everything together perfectly, but you need to make sure your moisture is right when creating the blocks.
This year I'm experimenting with well rotted pine. After sifted, It's about the same consistency as the "Coco Peat" but free and readily available for me. It's also inoculated with Mycorrhizae and should theoretically contain a better mineral mix. I just started some onions in the 3/4 inch blocks, I'll post an update here and let everyone know how it goes.
Free after initial investment
Less space (no plastic taking up storage, or cell space)
Less water (if done right the blocks absorb and hold on to water better than plastic pots)
Faster transplanting and potting up
Less transplant shock
Higher initial investment
Takes some time to get the consistency and mix right
Won't work with garden soil (clay will turn these into hard rocks)
Once the plants are bigger, staples come out and the cardboard will be used in a sheet mulch for some of the same plants.
Overall, I liked it. The total absence of transplant shock, even under bad conditions, was great. Some batches disintegrated a bit; (the consistency and moisture level of the mix is important) and watering them was difficult. I found that by lining a tray with plastic and flood irrigating them, it worked a lot better.