Lowering the PH of Soil

Hello Fellow Growers, This is my second grow, and i'm still having trouble lowering the PH of my soil, which I am sure is what is causing the yellowing of the oldest leaves then them dropping off. On my first grow I asked for advice on which soil to use for growing and was told John Innes No 1 for starting seedlings and vegging and John Innes No 3 for flowering. The trouble was the PH was 7.6 on the No 1 and 7.4 on the No 3, I then got some Chempak Sequested Iron and put at the top of the containers, which did lower the PH slightly, but the run off when I watered them was a deep red colour ! Now I am on my second grow and read that alot of growers use Bio-Bizz All Mix, So I got some, things seem to be going fine then the leaves starting going yellow again ! I took a PH reading and the Bio-Bizz All Mix seem to have a PH reading of 7.5 even though it said a PH of 6.2 to 6.6 on the bag. I've even got another soil PH tester and it still reads 7.5. I read that Gypsum is good to lower soil PH but I can not find it over here in the U.K. Is there an alternative that I can mix in / add to with the soil that will drop the PH of the soil. Can someone please help ! Many Thanks.

yes there are a few solutions but it sounds weird to me that all of these products had a high ph. i would get a different brand meter before doing this

Two materials commonly used for lowering the soil pH are aluminum sulfate and sulfur. These can be found at a garden supply center. Aluminum sulfate will change the soil pH instantly because the aluminum produces the acidity as soon as it dissolves in the soil. Sulfur, however, requires some time for the conversion to sulfuric acid with the aid of soil bacteria. The conversion rate of the sulfur is dependent on the fineness of the sulfur, the amount of soil moisture, soil temperature and the presence of the bacteria. Depending on these factors, the conversion rate of sulfur may be very slow and take several months if the conditions are not ideal. For this reason, most people use the aluminum sulfate.
Both materials should be worked into the soil after application to be most effective. If these materials are in contact with plant leaves as when applied to a lawn, they should be washed off the leaves immediately after application or a damaging leaf burn may result. Take extreme care not to over-apply the aluminum sulfate or the sulfur.

Click to expand...

Thanks for the reply and information norcalkronic, I will get a different brand soil PH meter before trying the aluminum sulfate & sulpher. Thanks again & Happy Growing !

you could use a little dolomite lime it will bring you ph down or if you can get fox farm ocean forest soil 1 cup soil 1/4 cup perlite ph 7.0

7.5 ph is actually workable in a soil grow, check out this chart to see what your plants are capable of.
Dolomite lime will balance your soil at 6.5-7.0. There is dry dlolmite lime which you would want to mix 1 ounce per gallon of soil to the top few inches then giver a watering, this makes the lime run through the soil. There is also hydrated dolomite lime. Try balancing your soil this way because it will NOT hurt your plants at all and your ph will not do major flucuations. I usually mix this with my soil at the start and at 4-5 weeks into flowering.

Also check out these links before you make a change, they may point you to something more synister going on. This issue is very common and usually cal-mag problems go hand in hand. Read about calcium and magnesium.
Ganja Guerrilla's Hall of Marijuana Plant Abuse
Ganja Guerrilla's Hall of Marijuana Plant Abuse
https://www.rollitup.org/marijuana-plant-problems/125478-maximum-yield-article-october-08-a.html

thanks brasmith. very handy links. one thing, in the ph chart, what does the orange bar stand for? i cant see the text, its unclear.

The orange bar is manganese (Mn).