Im trying to essentially make home made “pro mix” potting soil which boils down to peat, perlite and some lime to balance pH which is essentially the same thing as cornells soilless mix. According to online, Cornells recipe is 1 bushel of peat moss, 1 bushel of perlite and 1/2 pound of dolomitic limestone + fertilizers. Has anyone tried this recipe out?
In addition, Just to confirm because ive seen to answers online. A bushel is considered 8 gallons in volume?
thats how i make mine. for fertilizer i use either osmocote plus or a quality soil conditioner. if i have some worm castings ill throw some of that in as well.
So you use the ratio?
8 gallons of peat moss
8 gallons perlite
1/2lb of lime
After you initially mix this do you ever measure ph or add more lime in throughout the years?
i havent but it must be near neutral ph as everything ive used it for has grown well. when i reuse it as potting soil i always add a little lime to make up for what the plant before used up.
I sometimes use peat moss in my mixes, but never add lime. I add an equal amount of compost or garden soil, that is enough to make mix about 6.0 which is perfect for me. I mostly need it for fig trees which like slightly acidic soil. And yes, I tested soil. Since I mostly water them with tap water which is filled with carbonates, I worry the soil will be become too basic. I used peat this year, but further batches I will be using potting mixes that are mostly peat for the rest of the year. Such as Pro-mix general purpose. I would not worry about pH if using tap to water your plants. If you have well water that depends what is in it. I also save rain water, but I rarely water the figs with it as I need it for my blueberries, which only get rainwater.
My soil mix is
3 parts pine bark fines
1 part peat or potting mix
1 part compost or bagged garden soil
1/2 part DE the size of perlite. I like it way better than perlite for it’s water retention and the silicon it adds to the mix (shown in studies to improve plant growth).
pH is usually around 6.0 to 6.5
For blueberries no potting mix (peat only) or compost or garden soil, otherwise the same. So for blueberries
3 parts pine barks fines
2 parts peat
1/2 part DE
Soil pH of this mix is about 5.5 to 5.0
I have been doing these mixes for 6 years now and very pleased with results.
Fig leaves look great
unfortunately, i cant get decent compost or bark fines here. i mostly use chic bedding as a mulch on top and it composts in place. ive never ph’ed mine as it grows well for me. i do use the coarse d. e also just use alot less of it as perlite is much cheaper here. all my raised beds have d.e as well. i got those ph strips you recomended Drew. i plan to go around to my problem areas and ph them 1st before doing a soil test.
How many inches of the blueberry mix do you have in your raised beds before the native soil?
@Drew51 … where do you find DE the size of perlite? I use the powdered but would like to find the product you mentioned. Sounds perfect.
Just throwing it out there, dolomitic limestone, aka dolomite is relatively slow to release its alkalinity versus standard limestone. We avoid using dolomite in our mine drainage treatment systems and try to stick to limestone with 90%+ calcium carbonate as it is readily available from some of the quarries locally. I’m sure in soil it will eventually increase pH but if buffered adequately with other components I wouldn’t be as concerned about it.
My mix recently has been approximately:
-8 parts somewhat composted woodchips (free)
-2 parts horse manure (~7.5 pH last tested, would add
more if lower pH, free)
-1 part perlite (Ace hardware with coupon)
-3 parts diatomaceous earth chips (Grainger, zoro via eBay)
-6 parts peat (home depot by the bale)
-1 part coconut coir (Amazon)
-osmocote 6 month (Walmart recent deal)
-hollytone (clearance 2021 at Lowe’s)
-pellitized gypsum (tractor supply)
Everything is eyeballed but this is a good guess, I have been putting everything in a wheelbarrow and stirring with a shovel. Any ideas on a faster way to make a batch in the garage? This has been mostly going in potted bench graft containers. Also of note - I probably wouldn’t include the manure or wood chips if I was paying for it, but both are good fillers that serve the purpose well.
Ep Minerals 8925 Universal Absorbent,25 Lb.,Bag $10.99/bag with free shipping over $75 (7 bags)
Ebay via zoro or I think it’s the same deal on zoro.com
Where do you get your perlite cheap?
Originally the beds are 12 inches high and I filled them with my BB soil. It’s been 9 years now and I treat with sulfur about every other year. As organic matter composts it becomes basic. One needs to re-treat areas from time to time. I mound plants as high as possible when I put them in.
Best price is Grainger, order online, pick up at store. Optisorb has the largest particle size. Best example of the product.
Not really, I use garbage cans to mix with a pitchfork, but I’m getting old and use smaller parts as I can’t lift as much as I used to. An old cement mixer is what a friend uses.
As I was typing I thought of a cement mixer. Also now as I’m typing, I bet an old washing machine or dryer drum could be retrofitted even if it’s spun manually.
I was using a garbage can to start but I stopped because it seemed easier in the wheelbarrow. I guess if you found a sturdy round can with a secure lid you could just roll it around on the ground and not have to mix “by hand”. The pitch fork is a great idea. We used to carry one around on the back of our work truck and it fell victim to our “If you don’t use it for 5+ years put it on the shelf” rule 
At home I think I’ll get more use with my current interests. I always forget how much lighter they are versus a shovel.
believe it or not, my local nursery. get a 4ft tall bag for $25. used to be $18.
i get mine at napa.
I have before too, I may need to now. I need more and ordered 3 bags and it’s still not in (only 1 bag, which I may need to go get). Up potting for me with over 200 containers is a continuous process that never ends.
I did lose about 5 plants over the winter for some reason? I think my dogs burned them to death.
As I said above, zoro via eBay is cheaper than grainger currently. I got mine yesterday, I think it was less than 24 hours turnaround time from ordering. I was impressed.
I will check out the swordsman when I get back from playing this weekend. Thanks!!
What is the size of the Optisorb particles…and do you have to worry about inhaling it? I’ve only used the common perlite which is too much like dust…so I’ve stayed away from it.
The current eBay price, via Zoro, is $10.99 plus $5 for shipping. You really have to appreciate any vendor who keeps the shipping low…and that’s low for 25 lbs of anything.
an eighth to a quarter inch.
