Ph of runoff in soil grow

Discussion in 'Organics' started by MDEVA, Jul 10, 2012.


    cannakis Well-Known Member

    So pH runoff Does matter. Spent hours yesterday testing Every type of soil. And each medium gave the appropriate results.
    Garden soil 6.7pH & 279ppm,
    Cow Manure 7.3pH & 257ppm,
    Hot super soil 4.7pH & 2,800ppm,
    ProMix 6.3 pH & 365ppm,
    and 4:1 PM to HSS 5.2pH & 777-1,200ppm.

    My tap water going in is 9.0pH & 201ppm. So there is Definitely something to be said of run off even in "organics".

    Though I must say FOLLOW DIRECTIONS! Don't listen to me listen to Pattanhabi and Greasemonkey and Hyroot these guys know their shit and follow the rules.

    I'm mixing about 3:1 PM:HSS and my girls looks great! That's as far as I will go. Spreading the rest of my HSS into the garden and waiting a While and Couple runs before I "amend" again.
    Lost frost

    Lost frost New Member

    I've jus exp the same issue I watered with ph at 6.8 and run off came out at 5.8 so perhaps that explains the issues I'm having, from how everything looks it appears I have a lockout in the soil it's to acidic, the leafs appear to have a phosphorus def?? If I am watering at ph 6.8 and run off is around 1.0 off wouldn't that suggest that the soils ph is locking out my nutrients and giving the ladies these issues? I could never figure out what it was til I checked the run off I mean that's the most logical answer I can come up with is the soil ph won't even suck up the nutrients (locking)?? Idk man I'm right there with u other than the ladies are actually showing signs of deficiencies

    Jozikins Well-Known Member

    Do a slurry test to determine soil ph after feeding, the run off tells you little due to cation exchange.
    Stink Bug likes this.
    Dr. Who

    Dr. Who Well-Known Member

    "Run off pH?" in the organic section!


    Picasso510 Member

    Simply because ph does play a huge factor in nutrient absorption hence nutrient deficiencies (or what seems like it) but really is just the lockout of a specific nutrient due to lack of right ph. And some cases are more severe then others depending on mediums and strains. But I do agree with you about READING your plants overall it's ideal to stay on point as much as possible to reduce the chances of running into any problems down the road why do you think the best and most professional growers tend to be meticulous when dealing with their babies yes cannabis plants are very resilient but you don't want them to just live you want them to THRIVE

    Picasso510 Member

    Also I'd like to add FLUSHING can do alot more harm then good, if anyone does not know the difference between flushing and "leeching" then I'd recommend looking it up. Someone pointed this out to me and honestly it makes alot of sense.
  7. I think I may be able to offer something to this conversation. For what it's worth. Both points are correct. You really don't NEED to check pH runoff if there isn't an issue. The reason for this is if you have a healthy soil in terms of microbes within the soil breaking down organic material...which turns acidic if you have a microbe problem.

    A proactive gardner always checks pH runoff, as well as keeping an eye on PPM. (But PPM is not as important, and thats a topic for another day.) Checking your pH runoff everytime and logging it will not only help you never have a pH issue but be able to see issues coming down the road ahead of time.

    This is my procedure:

    I log every runoff's pH with a spreadsheet. As well as the pH of the nutrient solution going in.

    Now you have to follow me down the logic I have come to for this reason. If 6.5pH nutrient solution is going into the soil and coming out as 6.8 then many would see this as on the higher end but still okay. However if you had 6.8 water and added an equal amount of 6.5 water to it, what do you think you would get? Something in the middle of 6.5 and 6.8. You definitely wouldn't get 6.8 out. So this has to mean that the soil is higher than 6.8, right?

    There is a formula that calculates what the pH of the soil is based on what goes in and what comes out. Then it suggest what the next feeding's pH should be to bring the soil slowly back to 6.5. The formula I made doesn't make a full adjustment to 6.5, it slowly arrives back to 6.5 so as not to shock the plant by changing the pH of the current microbes are living in too fast, killing large percentage of your microbial life.
    Screen Shot 2018-01-31 at 7.00.10 PM.png

    It's also extremely important you are collecting the right pH. This is only achieved by making sure the same volume of liquid is just enough to saturate the soil fully. This will give you a pH around what the half way point between what was in and what came out. You can never get a fully accurate reading of a soil pH, but it will give you a good indication of where it's at.

    I know that this works because it always creeps back to 6.5 and is stable once reached. I know it's probably not necessary but it is a full proof plan for finding issues and never having lockout due to pH issues. Never. It's hard to argue with results.

    I also don't just grow for personal use, so I have a lot more riding on the outcome of my crops.
    Picasso510 and Sapphyre like this.

    ShLUbY Well-Known Member

    lol this thread is hilarious. how the times have changed!

    welcome to the forum @John Edward Cossack

    Sapphyre Member

    Glad to find this thread.
    Hope I don't get burned for asking a question about why it sometimes goes the other way lol
    So, when you are growing in organic soil, and using organic feed. Making sure ph is consistent going in @ 6.3-6.5, not over feeding, and watering when (and with what) your girls are asking for....
    When you have a plant that is not looking happy, and you test your runoff PH and the levels have significantly increased, as have the PPm, what does this mean?
    6.5 to 7.9, and 900 to 1800 in this case. Generally this plant gets feed then water and has been doing great w that rotation until a few weeks ago.

    It is the second time I've seen it, and the first time, I was able to slowly roll down the ph and bring the plant back- but I want to understand why it is happening in the first place?

    I am looking for a more broad brush stroke sort of idea- the other ladies are looking fabulous but there is obviously something that I'm missing?

    Do I just need to stop being lazy and get my teas brewing? ;)
    Last edited: Feb 2, 2018
    Dear ol" Thankful Grower!

    Dear ol" Thankful Grower! Well-Known Member

    In many soils even building your own there are buffers which allows the plant to break down food and absorb it I don’t bother ph run off only when I feed I correct ph for nutes ph ec and ppm are more preferred in hydro systems or coco soil is more forgiving
  11. Okay so if your feed is going in at 6.5 and coming out 7.9 then that means 7.9 is the middle point. Meaning to calculate for your actual pH soil the equation would be

    x = (7.9 - 6.5) + 7.9.

    "x" is the actual pH of your soil before watering it.
    "7.9" is the out
    "6.5" is the in and we subtract "7.9"(out) from "6.5"(in) to get the difference. Then depending on whether or not the runoff came out higher than the input or lower would determine if we add the difference to the runoff or subtract it.

    If your runoff came out more acidic (for instance: 6.5 in and 5.0 out) the equation would be x = (6.5 - 5.0) - 5.0.

    The idea is to think of the runoff pH as the middle point between the water in and the soil. So that if you put 6.5 water into 3.5 soil your runoff will be 5.0.

    I ignore PPM's unless they are super high from the rest of the plants in the same run and they look ill. Usually this is a lockout due to high pH though. PPM's are also important if they are dropping. It means your ladies are running out of food. Other than those to things I don't worry about PPM's.

    One of the growers I talk to out by me says that his PPM's came out 12K one time and it was the best yield he ever had. How much of that is true idk, but I do know that not everything that works in someone else's garden will work in yours. I just know this formula works in my garden.

    The pH of the next feeding runs off of this formula. It grabs the pH of the soil (that was our "x") and then calculates the soil pH's opposite so that the two mixed equal 6.5 and then divides that difference by half, so as to gradually adjust the pH. If it's something absurd like 3.5; I'll be more aggressive
    Sapphyre likes this.

    ShLUbY Well-Known Member

    do yourselves a favor, buy a bluelab pH soil pen and get an accurate reading and stop playing the chasing game and figure out how to permanently solve the solution. you guys are doing too much work. Believe me. get a pH buffer for your medium and you'll stop having to guess and change your values all the time. it's pretty simple soil science.

    dolomite lime in peat based mix 1/4-1/3 cup per cubic foot on the initial mix will hold pH just below 7 for an entire flower cycle when mixed in at transplant (each watering at 6.0-6.5 will dissolve a little dolomite and buffer the pH... no more guessing). the companies don't put enough lime into the peat mix to last an entire flower cycle because it all dissolves because of delivering an acidic watering. if you read too high, CaS (gyspum) will lower your pH (sulfur is an acidifier, again the buffering thing). scratch it into the surface and it will start to work with successive waterings.

    Now i don't grow with bottles anymore, but when i did, having the soil pH pen was a great investment. and learning about soil buffers and soil science was also of great value. When i compared run off pH, vs what the pen read for soil pH, the numbers were not the same, as John has keenly observed just as i did with the runoff. By adding buffers to my medium, i stopped chasing, and confidently maintained steady pH through the whole grow and my yields skyrocketed.

    Hell I even check my living soils pH now and again just for funzies. but not having to measure out nutes from bottles, check ph's, worry about all the other stuff that comes from bottle feeding..... that was the best investment of a lifetime! now its just plain RO water from start to finish :)

    even 2 weeks ago, i noticed some yellowish new growth in the tops of my plants i just put in the no-tills that have run a few cycles. suspected Fe def. checked the soil pH.... low and behold it's above 7 (Fe insoluble above 7ph), threw in some gypsum and one week later, plants are super healthy because the pH dropped and Fe was available again.

    i'm not saying that johns methods do not work, but they are too much work. and the result is crazy pH swings in the root zone if your pH is out of whack until a balance is reached (if it ever reaches a balance).

    good luck guys and happy growing
  13. I agree. This method isn't for your average grower or noobie. It's too complicated for the results that you do get. Like you said, watering with pH 6.5 every time or 6.3 will work just fine for everyone.

    However it's different for me. I am a computer programmer so all of this is done automatically by a raspberry pi computer. The nutes are mixed, adjusted and the pH is tested logged and then drained. All calculations are automatic. Furthermore I have found a 10% increase in yield depending on which pH my girls prefer best. I can also tailor availability of certain nutrients at a certain pH.

    It also wouldn't be too hard for someone to create a spreadsheet and simply type in the runoff every time. It's especially useful when you have an actual pH issue. A lot of times people wonder what pH to water at to get the pH back under control. Well this formula does all the calculations for you. Like many "tricks" in the cannabis world this isn't a useful tool for plants without issues. This is a useful tool to see those issues coming and be able to nip it at the bud.

    I too use pH buffers in my soil but I use those more as an insurance policy for rogue soil pH. Like I said, I tailor each strain of mine to a specific pH at certain times during my grow. This was something I could easily do with hydro but for my soil gals I needed to devise a proper equation for A) accurately finding the soil pH. & B) accurately adjusting it.

    As far as soil pH meters go, I personally think they are absolutely worthless. There are many forums on the topic of how off those meters are and how unreliable of a method it is to test the soil in this manner so I won't go into detail. Although blue labs makes a better version on the market. It's still just lipstick on a pig to me.
    Sapphyre likes this.

    Picasso510 Member


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