Bud density has more to do with light intensity first, before considering supplements . Potassium has a lot to do with hardening buds on a chemical biological level however, no amount of potassium will harden buds if the lights PPFD intensity isn’t what it should be . I use langbeinite for the potassium in my soil along with bio char annd wood ash from my grill.
im about to start making my own bio char because the latest studies have shown that coco coir bio char was the only bio char that increased yield and fruit size in a said by said study of three types of bio char. All other environmental details being dialed in also contribute to allowing the plant to live up to its genetic potential and that translates into bud density . . I’ve grown only 12 years at this point but I’ve tried 6-7 different nutrient lines in my gardens along with just choosing the right organic amendments mixed my way. All of the lines worked well when you follow their nute schedules and just cut the amounts in half . Then watch closely that you see no deficiencies. I started out DWC in the beginning , but switched to organic soil grown after the first three years .i was running 3 cycles a year at that time . It was my 7 or 8th cycle when I decided to try soil/coco mixed for the first time because I had so many extra cuttings I didn’t want to waste .While I did notice they grew a bit slower in soil than in water, and maybe didn’t get the yield as I did with DWC, the terpene quality, aroma, and flavor as well as the tricome production as well as the early flowering speed and vigor were increased using soil. Plus I discovered that soil was less expensive since it retains a lot of the nutrients used in it. That cycle was stellar in every way .i stacked that cycle . Stacking has more to do with light intensity during veg… the nodes need to be closer to each other to get stacks and you need light intensity for it. When PPFD is increased, the plant requires more food and water more often but the plant only uses what it needs to use and that is controlled by PPFD and humidity . You’ll notice that no matter what, your tops seem to almost always be nicer, denser and stacked better than the lower parts and that’s only because they’re closer to the light . Only after all those environmentals are dialed in as well as the humidity, and initial NPK should you be worried about supplements. They do make subtle differences in the end. I look at this way,,,,, I’m spending money on soil, nutes and electricity. All outcomes are dependent on the soil quality first, and that cannot be changed once the plant is established . So I focused first on making my soil mix as close to perfect as possible . Ianything you can do to increase oxygen and carbon in the soil will translate into better more vigorous yields . I spare no expense on the soil mix I use. I don’t see the point in growing unless you’re using everything necessary to increase quality and weight . When I say I spare no expense, I’m not saying I buy the most expensive stuff. I’m saying that I don’t do a run unless I have every amendment I need before I run it . The other thing is, with almost every product on the market, I’ve come to realize can be created organically with the right organic inputs but only when soil is given the proper amount of inputs combined with water and time . Give the soil 3 months to cook and when you plant , the plant will thrive because nutrients have been properly cooked by the bacteria’s and because the bacterial action is well underway by the time you plant . As far as PGRs are concerned, I use organic kelp . kelp is labeled a PGR now. I also use aloe. It helps roots and builds carbs in the soil . I believe I read that hormones in kelp and aloe are a major boost to root development and it’s those hormones that are the PGRs . And more roots-more fruits . I avoid synthetic PGRs . I don’t trust corporations to avoid poisons in their products . They’re about profit at any cost and that’s a recipe for disaster .