Jack’s 321 is our tried and true two-part fertilizer program. It consists of Jack’s Nutrients Part A 5-12-26, Jack’s Nutrients Part B 15-0-0 and Epsom Salts. BUT where does that “321” come from, you ask? It’s the shortened amount of each fertilizer in grams per gallon.
To mix up the perfect blend of Jack’s 321 you will need:
3.6 grams Part A
2.4 grams Part B
1.1 grams of Epsom salts
This will give you a blend of nutrients for growing almost any controlled environment crop, in any growing system. The order of additions is VERY important. You must add the 5-12-26 first and make sure it is completely dissolved, then add in the Epsom salts making sure it is completely dissolved, then finally the calcium nitrate.
-- bottom of page here.(<<link, feed charts are there too)