Soil pH Adjustments

Hi Everyone,

Last summer I ran into some issues with my soil pH being very low (<4.0) at time of early flower. I went through a complete flush cycle and had been using pH up to try and raise the soil pH with minimal luck. I was under the impression that i was over feeding my plants and this was the result of a salt buildup.

I just transfered my seedlings for this years crop into intermediary pots before i put them in the bigger pot, and since i had some leftover soil from last year (fox farms happy frog) i used that as the potting soil. When i stick the soil probe into the straight-from-the-bag soil (no water but not dry), the probe reads around 6.0-6.5, which is to be expected, but as soon as i add a little water to it, the pH drops down considerably to the 4.0 range and lower. What is also interesting is that the lower the probe goes into the pot, the lower the pH becomes (starts at around 5.9 - 6.0 at the top and sometimes reaching 3.0 at the bottom). I have not added any nutrients to this years crop, so i know that is not the issue. The water i am using is just Los Angeles city water (tap), which is around 7.1 in terms of pH. I am not sure if this phenomena is normal for soil with water, or if the soil is bad and i should just replace with new soil? Any ideas would be super helpful, as i don’t want to run into the same issue as i did last summer.

Thanks!

As far as I know, those probes are notoriously unreliable for readings. Try a pH test of the runoff from watering, first to be sure you’re not getting a faulty reading.

If cost isn’t an issue, I’d get new soil to be safe. Much easier than fixing a problem during flower.

If you aren’t using any already, good microbial additives help regulate the soil pH for the roots. Doesn’t mean you’ll never have pH issues, but it adds a layer of help.

1 Like

There likely isn’t anything wrong with your soil. Those meters do work… kinda. The moisture content has to be right for them to read accurately. If the soil is too dry or too wet they will give false readings. That is why you get different readings when you push the probe deeper. More water drains to the bottom of the soil. If I remember correctly you need to use the moisture setting first and get it close to the middle. Then flip the switch to PH with out moving the probe too much. That should give you a somewhat accurate reading. If you can afford a decent one I would defiantly agree its easier and more reliable to use a liquid PH meter to check runoff though. I think they are $40-50.

Thanks for the reply! I will definitely get new soil when i transfer to the bigger pots. I always thought the FFHF had solid microbial contents, but i will look into other soils too.

1 Like

I do have one of those, i just didnt really trust it. I will try a reading with that too and see what it gives me. But that makes sense for the soil probe needing the exact right water content. Ill see what i can come up with with the runoff. The runoff for last years crop was very acidic and i was measuring with the liquid pH meter, which is what tipped me off before.

Post a pic of this probe Growmie, if it has 2 long silver round probes…agree with the others. If you have a PH pen, run a soil slurry test…it’s the most accurate to checking medium PH :love_you_gesture:

4 Likes

It does. Happy is like the microbe life soil and ocean has all of the other stuff in it. Here is the back of the Happy bag with all the baci listed.
images
Happy

1 Like

Its one of those all in one probes from amazon that tells the soil dampness and the pH. I bought it to check my pH pen and it seemed to work but i still need to try with the pH pen to make sure the values are the same.

1 Like

I hate to say it Growmie but those probes are notoriously inaccurate. PH is super critical and has specific ranges for the different medium types. A few tenths out of range can prevent nutrient uptake. Check out the Apera 20, very accurate, reliable and inexpensive :love_you_gesture:

1 Like

4 years or so ago i was having nightmares chasing #'s Ph ing. Changed to Roots Organic soil and Jacks and still havent had any Ph issues since. That soil seems to be so well Ph balanced. No spikes no drops. I will blame my inexpierance at that point but with the Roots and jacks i didnt have to be Mr. GREENJEANS to have a successful grow!

2 Likes

Alright, I bought that Apera 20 probe and it is much more accurate than what I had before, thanks for the rec @OGIncognito. I tested the runoff from my pots today and it still came back very acidic, between 4.2-4.5 pH and am still unsure as to the cause or reason. I tested the water by itself, and it came back as around 8.5 (very basic I know) both with the Apera 20 and with my pH drops that came with my pH Up/Down kit i used last year. So this is telling me that the soil is even more acidic than originally thought to bring 8.5 pH down to 4.2-4.5. I also measured the pH of the water solution with the nutrients added to it (nutrients still not given to the plants, just wanted to check to see where that was at in order to make sure I wasn’t going crazy and the water wasn’t super acidic from the nutrients), which came out to about 6.5 pH, which is the first good news i have gotten from this exercise lol. Any thoughts as to why the soil is so acidic? Could the microbes in the soil just be dying from being stored all year and creating an acidic environment? really not sure what to think or to do, but will prob just get a different soil for the transfer into the big pots, which may be sooner rather than later.

Additionally, should i hold off on feeding the plants the nutrient solution (FF Grow Big and General Hydro Cal/Mag)? Or should i just try to get them some nutrients even though the intake might not be totally there?

Thanks!

1 Like

You need to flush with a product called sledgehammer. Follow the directions to a T and allow your soil to “reset” you dont need to use cal mag in soil. Also, have you calibrated your pen? Look up a soil slurry test on youtoob and take a sample of your unused soil. Make sure that your pen is calibrated and you are using distilled water when testing your soil sample. Dont rush the time. Trust the process. If you just transplanted, just water with plain tap. 7.1 is what is my city water ph and i dont check ph but im organic and dont use salt based nutes. Im just curious and to what your numbers are. With a ph that low, your plants wont be able to take up any nutients.

2 Likes

Ill try the slurry test. That is the one i didnt do today because i didnt have time. I was poking around other forums online and found that FF soil is not to be measured by runoff due to the organic compounds in the soil itself, which will produce a highly acidic runoff when collected. Any confirmation of that at all? Another user said that FF customer service stated to perform the slurry test as well, but as long as the nutes going in are within range, the soil will balance itself out to be absorbed. Idk how much i believe that because the plants are constantly eating and if soil is acidic at any point, i feel like it wont absorb.

1 Like

Just to update, i performed the slurry test on the leftover soil in the bag that I have . 1:1 ratio of soil to distilled water and let sit for 15 mins per FF slurry test recommendation. I strained the soil to get the solids out and isolate the water, and measured a 4.2 pH. I added that water back into the soil to test again and got the same pH, so it does appear that the pH of the soil is very acidic. Guess my only solution is to re-pot with better soil. ill probably switch to organic nutes as well. FF has given me too many headaches over the past few years.

1 Like

I use Coast of Maine Stonington blend along with their veg and flower amendments. I supplement with teas also. I use dynomyco when transplanting also.