Help understanding testing pH of water

Discussion in 'Growing Marijuana Indoors' started by HighOnTheHill, Jun 9, 2009.

  1. Okay so I have a soil pH meter, which reads about 6.5. Everyone says they're inaccurate, so I went and got a water test kit... for fish aquariums.

    It's just the "add 3 drops and shake" kit things, but it's going to have to do for now.

    My understanding is its the water RUNOFF that's the most important in determining pH?

    My real question is, how important is the pH of the water going INTO the soil? My tap water tested out @ about 7.5 - 7.6 and my nutrient solution (FF Grow Big and SUPERthrive) tested out @ about 7.2. I know you're supposed to use a neutral water, but is the .2 really going to hurt it?

    I haven't tested my runoff yet because well, I haven't watered my plants yet. Going to wait on a reply to his.
  2. absolutely. this is the best way to determine soil pH.

    It depends. Is this plant going to be a long lasting mother plant for clones? If so, then yes, feeding it continually with a pH 7.2 (or higher) Grow Big nute solution/water for months and months will likely cause a problem.

    If you are just using the FF Grow Big while the plant is in veg for a couple of weeks, then you can likely get away with this. What nutes will you be using for flower? If you are going to use FF's Tiger Bloom, this stuff is VERY acidic, in which case you're probably going to have to RAISE the pH after making the nute solution even though your water starting pH is above 7. If you pH balance the FF Tiger Bloom solution to 6 to 6.5 (the lower end of the soil pH range), watering with slightly high pH water should balance out the pH 6-6.5 nute solutions so that it won't be a problem. This might be a reasonable work-around.

    However, let me say this: when it comes to pH and cannabis growing, a little prevention can save you a LOT of headaches later on in the grow. Adjusting pH really is not that difficult, and only adds a few minutes to the process of feeding/watering your plants. I'd buy some pH adjusting solutions and always feed it pH 6.5 water/nutes every single time. I think you'll be happy you did when you get into flowering...flushing and pH adjusting the soil mid way through flowering after you've already noticed some damage to the plant is going to be a lot more difficult to deal with than just adding a little pH adjustment each time you water/feed your plant. prevention is the name of the game.

    good luck.
  3. Thanks A LOT dude. Right now I'm just vegging these plants for another couple weeks. And yes I'm going to use FF Big Bloom/TigerBloom for flowering.

    I just re-tested my nute mix, and it is about a 7.2.

    I also just ran some hydrated lime through a plant, runoff tested about 6.6-6.8, it's just a "add 3 drops and compare the colors" test, so its kinda hard to tell :p

    Stuck my soil meter in the soil and its reading about 7. It WAS reading a ~6.2(it's not a digital meter), but then again it's also saturated with a hydrated lime mix.

    I thought 6.5-7 was ideal?

    Ugh, just need to get some pH up/down.
  4. a digital ph checker is a solid investment. it will save you much time and headaches

Share This Page