I made enough biochar to fill a 50 lb feed bag (the air permeable woven plastic type) and charged it with urine for several months, stopped with the urine for another 4 months or so, then ground it up using a small old metal drop spreader. I popped a wheel off, clamped it into a drill, and started grinding away. I yielded about a 5gal bucket full and spread that in with my tomato and pepper rows along with gypsum, azomite, and humates. They did well, but who's to know what was the magic bullet in a fire fight. I don't have any quantifiable data for you, but I think if I supplement biochar to one production block a year (4 blocks of 46ft beds) it couldn't hurt. My native soil PH is usually on the high side of the spectrum, so that data may not be helpful, but I do plan to invest in EC metering and a refractometer maybe this year, so that would be fun to track for myself.
I was thinking about this recently from a fire ecology standpoint. I live in California. Yeah... Anyway, I wondered if some technique of burning crop residues could be a beneficial phase in a field rotation on say a seven to ten year cycle. Similar discussion/changes happening here in wildland management. A fire cycle is part of our context and if I've been considering whether theres a role for that in no-till here.
You won't be able to do controlled slow burn with on the field crop burning and you may just end up fuming away your carbon leaving behind nothing but minerals. No Cec gain there just good ol' pollution. If you have access to good compost i would stick to that, it does the trick equally well imo.
Ditto, I'm keen to start adding some during bed turn over. The simplest method that I've seen to make it seems to be these Japanese Kilns: https://www.activevista.com.au/product/pyrolizer-150-litre-biochar-cone-kiln/
I've also been doing some research into biochar lately and found this field study informative, particularly the mixed results observed within each crop family. http://www.ithaka-journal.net/pflanzenkohle-in-kleingarten-resultate-2011?lang=en The Ithaka Institute also has detailed plans on how to create large amounts of biochar and how to charge the char prior to its application in the field. Their site is well worth a look. Hope that helps!
We added a few ounces of biochar with every turnover. Lightly rake it in or cover it with mulch. Just started it this year, but hoping it will improve our CEC.