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Thread: which pH chart is right?

  1. #1
    grow4fun's Avatar
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    which pH chart is right?

    What is the best pH for hydro for MJ during flowering?? On the internet you can find charts showing nutrient absorption through the pH range. But they’re all freaking different! And directly conflicting.
    See below:

    1) A chart from www.overgrow.com (guess they should know about pH for MJ…)

    2) A more commonly seen chart, taken from an orchid-growing website (this chart is the same as one that’s sold in grow shops around here)

    3) From an avocado growing website

    4) From the book Indoor Marijuana Horticulture ( I think by Jorge Cervantes)

    5) From a site that does NFT, in New Zealand

    Following the charts from Overgrow and from the book, the biggest P absorption would happen way low – around 5.3 would be optimal. According to other charts, the P absorption doesn’t even start to happen until 6.0 minimum – 6.2 or 6.3 even better. I am confused.
    I’m tempted to set it at 6.3. I don’t think that anyone’s actually scientifically determined this for MJ using the methods they do for other plants. So who knows; take a wild guess I guess.

    Was wondering what pH other people have used that gave the most resin production and smell?
    Attached Thumbnails Attached Thumbnails which pH chart is right?-overgrow.jpg   which pH chart is right?-orchid-site.jpg   which pH chart is right?-avacadosource.jpg  

    which pH chart is right?-book-indoor-marijuana-horticulture.gif   which pH chart is right?-new-zealand-nft-site.gif  
    "An expert is a person who has made all the mistakes which can be made in a very narrow field" -- Niels Bohr, Quantum Physicist

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  3. #2
    Herbus's Avatar
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    I think you can get a bit caught up in charts. Max overall absorbtion (macro and micro) occurs at about 6.3. An acceptable range is 5.8 - 6.8 PH. You will get your fastest overall growth (all other factors being optimal) more then likely in this range.

    Herbus

  4. #3
    Sinsemilla Jones is offline Registered+
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    Wink 4 out of 6 of those charts are pretty much the same, and they are for soil.

    The 1st (marked for soil), 3rd, 4th, and 6th.

    The 2nd (marked for hydro), and the 5th are for hydro.

    Best hydro range is 5.2-5.8, but it doesn't hurt to get out of bounds now and then.

  5. #4
    LOC NAR1958 is offline Registered+
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    There was a chart in our faq's that shows it for MJ. Hydro should stay between 5.2 to 6.2. I was told you can change to adapt to the stage of your plant. If you drop the nitrogen in the last of flowering then you keep it low as you can to absorb the nutes you want. In hydro this becomes more aparent the more you grow.

  6. #5
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    Sinsemilla Jones: love the name.

    The first chart above is dual, one for soil, one for hydro. The other 4 were all taken from webpages that were definitely, specifically referring to hydroponics (I'm not that stoned).

    "An expert is a person who has made all the mistakes which can be made in a very narrow field" -- Niels Bohr, Quantum Physicist

  7. #6
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    Herbus: were you referring to hydro or soil? (i.e. max. absorbtion at 6.3).
    "An expert is a person who has made all the mistakes which can be made in a very narrow field" -- Niels Bohr, Quantum Physicist

  8. #7
    Herbus's Avatar
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    Yes this is the Hydro section so I was just answering for Hydro.

    Herbus

  9. #8
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    "were you referring to hydro or soil?" I know, stupid question...... but that's the highest number I've heard so far for hydro.

    Started wondering about all this 'cause last week, after keeping my pH steady at 5.8 or lower (usually 5.4 - 5.8), I added some microorganisms which for a couple days made it 6.1. I thought I noticed an increase in crystals for the first time, but since it could have been other things I disregarded that observation (could've been the point in the cycle, had just increased res temp to the high 60's, added the bacterias, etc).
    That [6.1] pH only lasted 2 days, until a res change. Thinking that 6.1 was way too high, I adjusted again to 5.7 and continued on. The buds don't seem to be getting nearly as crystally as they should, even though plants look really healthy (deep green, no leaf spots/wierdness). Filtered water, 40% humidity, nutrient temps stable 68 - 70 F, quality nutes -- blah blah blah.....
    Anyway just as I was about to try high pH again, I saw all these charts (especially the Overgrow one that shows max P uptake at around 5.3).
    Since the 2 schools of opinion are really far apart, I guess I could just set it way high (6.3), then after one week set it way low (5.3). And see if there's a noticeable differance. Although with only 4 weeks to flower left, you can't really afford to waste a week.

    thanks for all the input
    "An expert is a person who has made all the mistakes which can be made in a very narrow field" -- Niels Bohr, Quantum Physicist

  10. #9
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    Oh also, an agricultural extension website I was reading (dealing with hydroponics) noted that at pH below 5.5 the nutrient salts will bind with each other making them insoluble. But I read one guy on a forum who swears by 5.2........ 'go figure'
    "An expert is a person who has made all the mistakes which can be made in a very narrow field" -- Niels Bohr, Quantum Physicist

  11. #10
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    I think it's okay to give your pH a little play room as long as you are checking it regularly. A small drift is completely natural. Think about a plant growing in the ground. There is no way that plant is being kept at the "correct" pH yet she's still going to thrive if taken care of. You can't attribute "an increase in crystals" to a pH change of .3 over only a couple of days. She is growing, of course she'll fatten up as she ages and will pack on the most weight in the last couple of weeks.

    I guess the point I'm trying to make is... if your plants look happy, healthy, and perky don't be so quick to nitpick your pH.
    "And though we'd eliminated the threat of the enemy flying planes into buildings, no-one was prepared for terrorists flying two buildings into the sides of planes. No-one was killed but a lot of people were surprised." -Time Trumpet, Episode 3

  12. #11
    LOC NAR1958 is offline Registered+
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    Listen to lemonboy sound advice. if it's going good don't change now with 4 weeks left and that's when trichomes start. Can you show us some pic's please.

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