Citric acid is a very good pH buffer (from basic swings), that is why I included it, as well as it's other great properties of helping keep P soluble, and it lowers pH.
Using a pH buffering system of potassium carbonate and citric acid works very well, they complement each other. The blog entries by Daniel explain why and proves the science.
The problem most people have with citric acid is they don't add enough to get the pH buffer qualities. You may want to read the two blog entries by Daniel, they prove how well citric acid can buffer pH. But > 0.01 g/L needs to be used ...
The other problem most people have is their NO3:NH4 ratio is crazy, like greater than 20:1. That means the roots are pumping out bicarbonate exudates like made, while only exuding H+ proton rarely (as compared to bicarbonates). If the growers NO3:NH4 ratio isn't suffeicnt, then little can be done to provide strong pH buffering.
Ideally we wouldn't adjust our pH except for maybe once a week, if that.
With my method (at least) 0.02 g/L is used because the pH starts high (from potassium carbonate and potassium silicate), so we can use much citric acid. I also included a second acid, sulfruic (for veg and early-flowering) and phosphoric (for full-flowering). I included the second acids to assist citric acid in pH buffering.
Also, the boost in P for full-flowering comes much from the use of phosphoric acid instead of sulfuric acid, that is why I can boost P a lot but not affect K really at all.
My formulations should work very well for all growing methods. However, for drain-to-waste NFT or aero one would want to reduce P a bit. And coco growers who can't flush their coco well may wish to reduce the K in my formulation a little, but I doubt it's necessary; coco growers may also want to add a bit more Epsom salt to increase Mg to keep the K:Mg ratio closer to 3 (due to high K in coco that isn't very well flushed). Otherwise, all a grower needs to do is adjust EC as I wrote in earlier pages.
Note:
I'm going to look into the chemistry of flushing coco, to see if using a strongly acidic flush would dissociate K from CEC sites with greater efficiency than using RO water. From my current understanding I think it would. Ex., I have read in academic lit. using strongly acidic pH (ex., pH 4) can dissociate (remove) cations (such as K) from "exchangeable" CEC sites due to replacement of cations by H+ protons(?) from the acid. That means if we flush with strongly acidic pH (re lots of H+) we should remove greater amount of cations from CEC sites, thus removing more K than otherwise if we only used RO water. Also, the volume of water needed to flush would be reduced using a strongly acidic pH flush.
I wouldn't use lemon juice, it's got other things in it and you don't how much citric acid you're applying. You can buy citric acid, like an ounce for ~$2 at any beer brewing shop; or you can buy larger quantities for cheap from JR Peters, Ebay, etc. It's so easy to use and buy citric acid I wouldn't suggest using lemon juice.
Exceptionally well, especially because coco has no pH buffering unlike s.peat which has dolomitic and calcidic limes add to it. So the pH buffering afforded by my formulations should really help the roots take up ions efficiently. Just make sure to flush your coco well, to remove as much K as possible (see comments above about low pH flush).
Because I use high Ca, Mg, and K, and sufficient Na, the Cation Exchange sites on coco particles should fill rather quickly, after flushing. Also, my formulations provide a good Ca:Mg ratio so the "Percent Base Saturation" should contain sufficient (and mostly) Ca, which is a good for soilless. The good thing about coco is the Cation Exchange Capacity (CEC) is not overly high, it's in the medium range, lower than s.peat, humus, etc. That means using my method, one may not need to 'pre-charge' coco after flushing the coco.
Don't use Head's old 6/9 mix, he has a newer mix with higher bloom. I wouldn't use HEads mix at all, use my GH mix for coco. And you can boost P in full-flowering with P.acid as pH down. Or use a bloom booster.
Yes, do 50/50 tap/RO, or 25/75 tap/RO. Then use my GH mix, not Heads.
If you have those, you can use my default values for K3CO3 and acids, and just use whatever source of potassium silicate you have. Once the pH is ~6.0, add the GH ferts. It won't be exact, but that's okay.
A mg (0.001 g) scale on Ebay is a cheap as $30. You will need an EC meter, everyone should have one. But it's not a rush.
pH of 5.8 isn't important, anywhere from 5.5-6.2 is fine. I would do the following:
Yes, but I would use pH 4.5 to 5, instead of pH 4, with living plants.
Increasing protekt is good to increase Si, that's the main reason I suggested it, and and the increased K is helpful. But you'd do still very well if not increasing protekt, it's really up to you. And yes, if you used more protekt you'd use more phosphoric acid in full-flowering, which would provide more P in full-flowering.
It was a typo, it doesn't matter what you use to lower pH for the final test (if it's needs to be lowered, it may not). I like to use citric acid, but you can use any of the three.
Have you gone to your local auto parts store? And asked for "Qual" battery acid (electrolyte grade sulfuric acid)? Or at least 35% battery acid? If not, try it and they should stock it. Call your local NAPA for Qual (here; most local stores only carry the 6 quart or 5 gallon jugs, which are inexpensive) or AutoParts2020 (6 quart for ~$14), etc, or go to Ace Hardware where you can get 6 quarts for ~$15, or get 1.5 gallon for ~$16 here. It's best to use 35% sulfuric acid, as it's the standard for horticulture and Qual has been well tested and proven effective in academia for horticulture.
I'm not sure about HomeDepot, but see above for sulfuric acid. You can phosphoric acid (pH down) at any hydro store.
always impressive spurr. if i ever switch to ferts i'll be mixing up some of "spurr's old fashioned"
