Organic Living Soil - High PH

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CannadaJ

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Hello All!

New grower from Canada. I've been gardening for years, and growing mostly hot peppers and microgreens for at least a decade. This is my first Cannabis grow (autoflower Sour Maui ).

I mixed a standard soil recipe consisting of 1/3 Promix HP, 1/3 compost/worm castings and 1/3 perlite. I added some inoculated biochar, Mykos and Fish Shit microbes, which I've been including in ever second watering. I let the soil cook for 5 weeks and tested PH throughout, which averaged around 6.5 (+/- 0.2). I water with Distilled water and check PH every time, which is usually between 6.3 and 6.6.

My plants showed really healthy growth, tight internodal spacing and one of them even reached 5 feet tall! The buds grew to a nice size and everything was fine. Then I started noticing all kinds of deficiencies on the leaves in mid to late flower. Brown spots, discoloration, edges burning, etc. I had just top dressed with Gaia Green 2:8:4 Bloom 3 weeks earlier and recharged the microbes throughout, so this didn't make sense.

I suspected a PH issue and decided to test the soil PH...and it came out at 7.8 and the runoff tested at 7.7. I'm testing with a well calibrated Apera pen (calibrate every watering just for good measure). I repeated the test twice in 3 pots.

What would be causing such a high PH in soil given that I am watering with much lower PH'd water, and started with a soil at 6.5?

I'll get a decent harvest, but want to avoid such high PH for the next grow.

Would love to hear from experienced growers, and thanks for your time!

Julien
 
Peat_Phreak

Peat_Phreak

391
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Normally the answer is bicarbonate from your water accumulating over time. But you used distilled water. So there isn't a bicarbonate issue. Plants can create alkaline conditions if they absorb nitrogen as NO3.

https://www.jstor.org/stable/42948425

I'm betting that is the problem. I use low bicarbonate water and the pH always ends up around 7.5 by the end of the grow. This is with the feed pH'd to 5.5 in acidic peat. Problems can start happening around 7.8. Right where you are.

Try using some acid producing microbes next time. You can do some acid flushing to lower the pH, but it wont work fast. It takes about a week to reduce the media pH by 0.2.
 
C

CannadaJ

4
3
Normally the answer is bicarbonate from your water accumulating over time. But you used distilled water. So there isn't a bicarbonate issue. Plants can create alkaline conditions if they absorb nitrogen as NO3.

https://www.jstor.org/stable/42948425

I'm betting that is the problem. I use low bicarbonate water and the pH always ends up around 7.5 by the end of the grow. This is with the feed pH'd to 5.5 in acidic peat. Problems can start happening around 7.8. Right where you are.

Try using some acid producing microbes next time. You can do some acid flushing to lower the pH, but it wont work fast. It takes about a week to reduce the media pH by 0.2.
Thanks!

The intro from that article was enough for me to start looking into NO3(Nitrate) vs NH4+(Ammonium) uptake and soil ph.

Given that my grow method seems to be a quite common one (organic living soil @6.5, distilled water ph'd to 6.5, organic amendments), any idea what would be causing nitrogen uptake as NO3? Is it possible I'm adding too many microorganisms and causing Nitrification? from this article http://cceonondaga.org/resources/nitrogen-basics-the-nitrogen-cycle

Nitrification is the process by which microorganisms convert ammonium to nitrate to obtain energy. Nitrate is the most plant available form of N, but is also highly susceptible to leaching losses


J
 
Peat_Phreak

Peat_Phreak

391
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That could be happening. I don't know for sure. I only grow in peat with salt nutes and don't know much about organic soil growing.
 
C

CannadaJ

4
3
That could be happening. I don't know for sure. I only grow in peat with salt nutes and don't know much about organic soil growing.
I'll keep checking the PH. I'm getting ready to harvest and start 2 more plants in another soil mix - currently reading 6.5. I'll monitor throughout the grow to see when and if the ph rises.

For this grow, they are almost at harvest so I'm choosing to leave them alone. They are dank, frosty, dense and massive. I'll live with that.

Thanks,

J
 
PotsieSativa

PotsieSativa

41
18
Normally the answer is bicarbonate from your water accumulating over time. But you used distilled water. So there isn't a bicarbonate issue.

1/3 1/3 clues me in to Coots mix. Limestone, crab shell, and more like stone. Plus the hot worm brands are feeding limestone. Definitely a carbonate problem. That recipe is a joke, telling people to add all that crap. 4 cups of limestone and silica.. The compost in my region has tested over 8ph. Wonder if it's also loaded with CaCO3... Clackamas Coot has ruined more gardens than I can count. And I can count to 500.
 
Skunk199

Skunk199

22
3
Hello All!

New grower from Canada. I've been gardening for years, and growing mostly hot peppers and microgreens for at least a decade. This is my first Cannabis grow (autoflower Sour Maui ).

I mixed a standard soil recipe consisting of 1/3 Promix HP, 1/3 compost/worm castings and 1/3 perlite. I added some inoculated biochar, Mykos and Fish Shit microbes, which I've been including in ever second watering. I let the soil cook for 5 weeks and tested PH throughout, which averaged around 6.5 (+/- 0.2). I water with Distilled water and check PH every time, which is usually between 6.3 and 6.6.

My plants showed really healthy growth, tight internodal spacing and one of them even reached 5 feet tall! The buds grew to a nice size and everything was fine. Then I started noticing all kinds of deficiencies on the leaves in mid to late flower. Brown spots, discoloration, edges burning, etc. I had just top dressed with Gaia Green 2:8:4 Bloom 3 weeks earlier and recharged the microbes throughout, so this didn't make sense.

I suspected a PH issue and decided to test the soil PH...and it came out at 7.8 and the runoff tested at 7.7. I'm testing with a well calibrated Apera pen (calibrate every watering just for good measure). I repeated the test twice in 3 pots.

What would be causing such a high PH in soil given that I am watering with much lower PH'd water, and started with a soil at 6.5?

I'll get a decent harvest, but want to avoid such high PH for the next grow.

Would love to hear from experienced growers, and thanks for your time!

Julien
Hey Julien, how big is your pot size? I myself run the clackamas coots mix and have had awesome result, don’t listen to the negative people who failed trying it. It works if you do it right just like bottle nutes. You really don’t have to chase your tail checking PH with organics. Honestly it sounds like you ran out of juice right at the end. This was my last run in a 15 gal clakamas coots mix.
 
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Homesteader

Homesteader

3,264
263
Add some 100% peat to the top of the bag which will drop your pH. I would say a couple of handfuls of peat (spagnum moss) should be good to drop down 1 but I am curious to how much biochar you added. Biochar is pretty much carbonate if I am not mistaken.
 
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