Making your own potting soil

[K.B.]

When we lived in the suburbs, we only needed a couple bags of potting soil a year to get our seedlings going that we would use for transplants.

With our bigger property we have not only a need for more plants, but the resources to pull on to make our own potting soil. There isn't any peat lying around or bogs to dig up, but we do have plenty of old fallen trees that can be put to good use.
To get the fine humus that we want for a quality potting soil we are sifting the rotten wood and combining it with a sandy silt from an area near the old creek bed.
We are using white oak, madrone and doug-fir deadfall for the most part. Before mixing it all together you get some nice color contrasts from the different starting materials.

Our old compost sifter set-up, does the trick. Basically it is just a series of wooden boxes about 2' x 3' put together of scrap 2x6's with hardware cloth for the bottom of the boxes. We have several of these to help sort the rough (larger) material from the fine. The one in the pic below is 1/2 inch mesh, I believe.


Here is a 5 gallon bucket of the sand-silt from the old creek bed. A little goes a long way. The sandy material is really just to make sure the texture of the potting soil stays loose and doesn't mat together.



These are a couple flats that have been filled with the mixture of the screened humus and sandy-silt (~10:1 ratio). Once the potting soil is in the flats, just enough water was added to get the mixture moist and they were ready for planting.



My sons were kind enough to help in getting some cold hardy seeds sown in the flats, so now that they are hanging out in a bright area (but not much direct sun at this point), until we start seeing some sprouts.

[sos]

xxx

[K.B.]

the more rotten and crumbly the better the yield will be, but so long as the wood is soft, it should be able to be used. Our rule that we're working with is that if the log is intact enough to pick up and not fall apart is goes to the hugel bed or soon to be mulch pile, whereas if it falls apart in your hand, its destined for potting soil.

A square shovel works really well for collecting these. A number of oaks and fir on the ground are just soft spongy humus inside a thick skin of bark that is all that is left.

I'd probably not pick cedar or cypress as first choice wood for potting soil, but by the time it's this broken down, I doubt it matters. the bacteria and fungi have had their way with it

[Autonomy Acres]

Great post KB. Seed starting soil is so important. It looks like yours is pretty nice. I still have not found a commercial blend that I like, so one of these years I really need to start mixing my own. Here is a nice link about mixing up your own seed starting soil, I love the use of a electric cement mixer, I think the Harbor Freight Tools by my house has one for $10.00!

[sos]

xxx

[Autonomy Acres]

sos - The one I am talking about would be purchased brand new, and concerning mixing cement in, it would be worthless. It is made out of plastic, with a small electric motor. Perfect for mixing up potting soil, check out the link I posted (it is from Powering Down.)

[K.B.]

A week later plus some sunshine and water...lots of seedlings are up!

Very good germination, overall. The bunching onions, cress and the little gem lettuce were the clear winners for speed. Followed by the cabbage, kale, collards, cardoon, purslane, roselle hibiscus, leeks and savory. The brocoli, chives and rhubarb are making their appearances, now. That leaves just the cilantro and parsley to yet make their appearance. Parsley is often slow for me (1-3 weeks), but the cilantro should have been up by now. I'll start another handful to confirm, but I suspect I will be getting some new seed. It's not more than 2 years old, so I am surprised it did not germinate.





Some true leaves on the oldest plants are just starting to develop. I'll keep an eye on the color and see if any are showing signs of needing some nitrogen and add a scant pinch of bloodmeal or manure tea if necessary over this next week.