How to maintain a steady soil pH

Hi guys so I’ve had two grows now that got messed up by super low levels in my soils pH. I recently figured this out to be the culprit of some damaged grows this year. Now that I know what it is though i’m not sure how to really prevent it from happening. I hardly gave any mixed nutes to a grow I have going in the tent right now and it’s soil went all out of wack and got super acidic. I use Fox farms Ocean Floor soil. Any tips on maybe how to remedy the soil before planting or anything I can maybe do to remedy during growth. But really anything at all really would be really appreciated!

Do you check the ph of the water going into your plants? I used FF nutes last grow and my soil went acidic also. I had not been checking ph of water going in. FF tiger bloom very very quickly in small amounts will drive ph down into the 4s.

Once I got a ph tester I started watering at ph 6.5 and after flushing with ph 7.0 water I was able to get my soil runoff to about 5.8 which seems to be acceptable

1 Like

@Gooseman1324

Measuring the pH of soil / soilless runoff

How to test the pH of your soil mix

The pH of soil is just as important as with hydro applications, but few people know how to test soil pH to see if it is within the optimum range for growing robust healthy plants. Here I will try to explain my method of testing any soil / soilless mix, enabling me to spot any problems and correct them if necessary.

Firstly, wait till your soil has dried out and is due for its next watering schedule. Then take some plain water that you usually water your garden with, and adjust the pH to 7.0. You must make sure that you know the exact pH of the water going into your soil, and the neutral 7.0 is best, but anywhere from 6.5 – 7.0 will suffice.

Then place your pot into a bowl of some sort to catch the runoff water, and then start to water your soil slowly (with your pH- corrected plain water) till the water starts to drip from the bottom. It’s the first drops of water that will give you the best reading of your soil, so make sure to water slowly till you see the first droplets. Then remove the pot from the bowl to eliminate excess water entering the bowl. Then perform the pH test on the runoff and compare it too your initial test.

The results of the runoff test will likely be lower than your starting value of 7.0. If this is the case, a small drop of 0.5 pH to 6.5 pH (example) would be ok and your soil needs no further alterations at the moment. But that’s not to say that it won’t need any future tests at all, just not at this time.
[Editor’s note: It may be beneficial to obtain an initial sample, as well as a ‘full flush’ sample in separate bowls. In addition, test several plants in the garden just to verify your results]

What if the pH is off?
If your results prove to have dropped considerably, say to around 5.5 (which can happen in late stages of flowering), you will need to add some lime into your soil to help buffer the pH back up again.

Remove the first inch or so of soil, taking care not to damage any roots whilst performing this task, ensuring that your pH is correct should be done throughout the life cycle; this will help eliminate any nutrient lockout that may occur. I recommend doing this once a month just to keep the PH in check, and you should never have a problem with deficiencies caused by pH lockout. Then sprinkle the lime into the pot, nice and evenly at a rate of 1 teaspoon (5 ml) of lime per gallon of soil. Then replace the soil you removed earlier, and saturate the soil good to wash in the lime.

Do the same test next time your plants need watering just to check that everything is fine, if more lime needs to be added then just repeat the process again till you reach close to 6.5 – 7.0 with the runoff.

If living soil using natural nutrients there will be a range that it will have from 5.5 to 7 assuming there is a healthy micro heard population.
Look up soil slurry to check your soil PH before planting or while it’s growing.
Use RO or distilled water when performing the slurry test and make sure your liquid PH pen is calibrated first.
If a living soil with proper balance of nutrients it will self regulate. I use RO water as base and haven’t checked PH of any solution I mix for many many months and let the critters in the soil do their job maintaining things.
If your using man made chemical nutrients you’ll need to deal with checking PH and PPM all the time.

I use a soil test probe from time to time and it works very well. Costs is around $70 but don’t use it much anymore. Only if an issue comes up. Haven’t used those liquid PH pens in probably a year or so.

I’ve replaced using dolomite lime for the most part (don’t use hydrated lime) with oyster shell powder and Gypsum for calcium and sulfur. I will use Dolomite Lime if needing to raise the soil PH quicker.

Grow organic with a living soil and throw all that extra work away with PH and PPM and flushing etc etc etc.

It is my understanding the first part of the runoff is least representative sample of the whole. It seems the first runoff either comes down the sides or out the side of the bag no matter how slowly I pour the water.
Soil with a high peat content tends to do this until it becomes rehydrated. So, I may test the first runoff to see what it is. And then continue watering and retest. If I water with 3 liters I want 300 - 500 ml of runoff for the test.
The .5 change in ph over time is also my threshold. If it changes more than that, I take some type of corrective action. Usually an immediate application of additional ph water.