If I remember correctly it was blueberries that you had the most trouble with. Since they need special treatment and much lower pH than most plants, I don't see how we can answer your question without knowing what you intend to plant. It's also hard to determine the pH of your mix without knowing the pH of the compost. FWIW, I figure you have about 170L of mix which is about equal to 45 gallons US. If it was standard 5-1-1 and not being used for blueberries, I would tell you to add about 2/3L of dolomitic lime.

Hi lightning....according to David Liddle, most hoyas grow in a somewhat acidic medium. However, you're right, the eriostemmas seem to grow and bloom much better with lime added to the potting medium. Many growers, myself included, add pellitized lime to the potting medium...and use this for all plants. You may wish to also add charcoal to your mix....lime and charcoal are commonly added...it prevents the mix from getting "sour". Just be careful to not over do it. You can either mix it into the mix, or sprinkle a teaspoon on the surface of a 6-inch pot. Some people have tremendously great results doing this, however, I haven't really noticed a difference so far. Hope this helps. Fondly, Patrick

I have bought a pH test kit from Petsmart that is pretty good. It is a solution that you add 3 drops of it to prepare soil sample solution in the test tube ( in liquid form ). It comes with pH color chart that you compare your sample next to it. This kit is sold/used to check fish tank pH . Last year I did some of my own tests also had done by professional lab. They were virtually the same. the kit cost like 7 bucks and you can make 250 tests with it. With the soil pH you don't need to be dead accurate. Even a half a point deviation on the pH scale should be good enough for gardening purpose. Sey

I wanted to update my post with some info I stumbled upon. There is such great info on this forum but with so many threads they are hard to find. I hate repeat posts questions previously answered questions so least I can do it update with info I've found. 1.). When it comes to fertilization I get easily confused. My original question about Gypsum (#1) didn't even address Epsom Salts which were also relevant. User mblan13 answers this gypsum question regarding pH levels. But in this link from 2009, just 3 post replies down (unfortunately I can't seem to link to specific posts in a thread), user cebury asks another question regarding gypsu: "Al, I typically see your Gritty mix recipe (with gypsum) include the caveat of adding Epsom salt when fertilizing (for Mg) but only once have I seen you say "if you use Foliage Pro 9-6-3, don't add Gypsum or Lime in the original mix at all". Was this out of context or does FP provide enough of all the Ca,S,Mg nutrients to not use gypsum when originally mixing the gritty mix? I'm only speaking to the gritty mix since I know liming the more organic 511 mix also addresses pH issues. Would there be any noticeable effects when doing both (having added gypsum at 1tbsp/gal to gritty mix and also using FP in 1/4 of "maintenance dose" at each watering)." To which Al responds: "I do just that (add gypsum + use FP). I don't know the exact reason WHY, but I have discovered that plants in the gritty mix seem to grow better across the board if I use gypsum when I make the soil, whether I use MG (which lacks both Ca and Mg) or FP, (which includes both). I add the Epsom salts, even when using FP, to keep the Ca:Mg ratio in line so no antagonistic deficiencies develop. It may be that if you use the gritty mix with only FP and no gypsum, that the starting pH of the gritty mix is low enough that the Ca fraction of the FP remains reactive and largely unavailable. The added gypsum/Ca is probably simply increasing the actual presence of Ca just enough to ensure there are no pH related deficiencies." It's worth noting the first two replies were from Tapla himself answering the request for the Gritty Mix recipe with his second post correcting his first post and saying there is no need for Gypsum. I imagine his experience is through trial and error and perhaps correcting himself stating it's not required is the easy solution for what could be us readers over-analyzing in search of a secret which is really just found through time and experience. I am certainly guilty of that and would hate to deter such experts from posting here out of fear of being pummeled with additional questions. I hope they would let us know if that's the case. Still, Al mentioned his uses gypsum anyhow because his plants seem to respond better although he isn't sure why. He theorizes it may be due to correcting for low uptake of Ca possibly due to low pH but then wouldn't my original question about using Dolomite Lime in place of gypsum be the perfect solution? I see FP includes 2% Ca and 0.5%Mg. In Al's response in my linked thread he states he uses Epsom salts to keep the Ca:Mg ratio in line. I assume that means 1:1 which for some reason DynaGrow must not be able to manufacture otherwise I would assume they would have. All this certainly makes my head hurt. I'd love to know if it's simply me over-thinking or if I'm on to something. And this is just question #1 on my original post :)