I'll answer from 2 different perspectives, one being the physical structure of the soil and it's properties, and the other being my personal experience with CHCs.

I have grown several cuttings of the same plant side by side in mixes that had as their primary fractions CHCs or pine bark. In every case, the pine bark mix did much better than the mix with CHCs. FWIW - I even tried rinsing the CHCs and then soaking them in a mix of CaNO3 and MgSO4 as many of those that use CHCs do, but the results were the same. It's not that the plants didn't do ok based on their stand-alone appearances, it's just that the plants in CHCs were much smaller and had a weaker appearance than those in the predominantly bark mix, which has led me to believe that even though CHCs might allow me to produce satisfactory plants, the side by side comparisons indicate a difference between bark & CHC mixes in the plant's ability to grow at as near as possible to their potential.

It's possible that if I was determined to overcome the limitations seemingly inherent in CHCs that I would eventually discover methods that allowed me to improve results, but simply exchanging CHCs for PBFs in the mixes I've tried just hasn't worked as well.

From the structural perspective I think that if you keep your combination of CHCs and perlite to greater than 80% of the mix, and the combination of compost and peat to under 20%, that you'd have a soil that allows you to take advantage of the higher aeration a soil comprised of primarily large particles offers.

I think I would skip the CaC03 tablets because they can drive pH higher, and with CHCs already coming in at a pH in excess of 6.0, you really can't afford a Ca source that raises pH; including dolomite. If your fertilizer source doesn't include Ca (or Mg), I would stick with gypsum as my Ca source because it doesn't significantly impact pH (and include Epsom salts [MgSO4] as a Mg source for the same reason).

Best luck!

AL

Thanks Al for the reply! I actually did read through your previous post on pine bark fines vs CHC comparison AFTER I bought the huge bag of CHC so....I can only try to make the best use of what I've already got now until next time. A question about the amount of gypsum and Epsom salts to be used: I understand the amount of gypsum to be used is 1 tbsp per gallon of soil - is this "soil" referring to just the CHC or the whole potting mix? Also, I can't seem to find how much Epsom salts should I use to supplement the mix.

Use 2 tsp - 1 tbsp of gypsum mixed into each gallon of soil when you make it, unless your fertilizer contains Ca. If you're using a soluble fertilizer w/o Mg or Ca (like MG), add 1/4 - 1/2 tsp per gallon of fertilizer solution each time you fertilize.

Al

Hi Al, any chance you've had another look at CHCs? Here in Bangalore it's impossible to find bark fines, though CHCs may be slightly easier to obtain. Perlite, vermiculite, expanded clay pellets are all quite expensive here too, as the conventional practice is to simply use super heavy, clay-like red garden soil for potted plants. Or best case, this soil mixed with coco peat, which guess what, is added to *improve* water retention. Needless to say, I've killed most of my favourite plants in less than a year. I've been now keeping an eye on my soil, and the bottom layers hold on to water for at least 10 days! Clearly, this situation a disaster. Do you think you could tell me what experiments I could do to see where the coco chips lack with respect to the bark fines, and perhaps figure out an affordable solution to a balcony container garden?

BTW thanks for all the great posts here, they've been super informative!