Bad soil? Very low pH

[Vancho]

The thing is I already suffered from calcium lockup by low pH in two different crops. Using the same soil, one from my zone (Growmix multipro), a mix of perlite, vermiculte, compost and moss peat. Tested de pH: firs crop 4.6-4.8, second crop 4.2-4.6.
Humidity 40-50%, temp 23°C, medium-hard tap water, fertilized with Top-Crop (spanish brand). Lights COB leds white+full spectrum (600w per square meter). Strains from requiem seeds and royal queen seeds.
Also, and I don't know if its important, lights were off very often for multiple blackouts in the area. The timers got delayed as well.
I've been using this brand for almost 3 years and nothing happened before...
What do you all think?

 

[AllStuff420]

The problem with cannabis plants is that they can only absorb nutrients within a narrow pH window, which ranges from 6–7 when grown on soil. If the pH is too low or too high, the plant will not be able to absorb nutrients, even if they are there. As a result of "nutrient lockout," nutritional deficits are exacerbated. The pH of the substrate is crucial in plant nutrition because it directly affects nutrient availability. Substrate pH levels below 5.0 increase micronutrient availability, which can result in iron (Fe) or manganese (Mn) toxicity, or both.

 

[Creeperpark]

No it's not bad soil you just have to raise the intake water to allow nutrient absorption. Use water that has a pH a little above 7.5 and it will stabilize. Don't feed the soil fertilizer because it is already charged with plenty of nutrients. The 7.5 pH water will raise the 4.6 to 6.2 after a few waterings. Keep checking it after every watering to monitor the results. If you feed a soil that has a fertilizer charge already in the soil it can drop the pH into the 4s.

 

[Creeperpark]

A few ways to buffer water pH, are by using cal-mag or a tiny amount of dolomite lime bubbled in the water, or tap water will raise the water pH.

 

[troutman]

Luckily, raising pH is easy.

 

[Three Berries]

Potash, aka fresh dry wood ash is quite basic and makes a good topdress to adjust your pH up.

 

[Creeperpark]

Potash, aka fresh dry wood ash is quite basic and makes a good topdress to adjust your pH up.

Wood ashes are good in some cases but not all. Wood ash in containers can cause problems. Wood ashes will raise the pH and lower the acid in the soil. Because of this, you should also be careful not to use wood ashes as fertilizer on acid-loving plants like cannabis in containers. It's like throwing darts with a blindfold on because it's hard to know how much to use or not to use. For that reason it's best to modify your water to raise the pH.

 

[Three Berries]

I didn't know cannabis was an acid loving plant. Regardless if your soil pH is too low then then wood ash is excellent. Don't use unknow wood. i have plenty dead ash trees around.

You can add it to the water too.

 

[Creeperpark]

I didn't know cannabis was an acid loving plant. Regardless if your soil pH is too low then then wood ash is excellent. Don't use unknow wood. i have plenty dead ash trees around.

You can add it to the water too.

An acid loving plant is a plant that prefers a pH below neutral. Anything under 7 pH is acidic.

 

[Three Berries]

LOL but if you add any nutes you are adding salts which will bring pH down. Just how do you raise the pH in soil? Add -OH of some sort. Carbonates or Potash.......

Forgot NH4.

 

[xet]

Love Gypsum https://www.eco-gem.com/gypsum-remediate-saline-sodic-soils/

 

[Three Berries]

Love Gypsum https://www.eco-gem.com/gypsum-remediate-saline-sodic-soils/

Last house repair I did I piled up all the drywall out by the burning pit. 5 years of decay and it is in a nice crumbly condition. I use a bit now and then.

 

[TanzanianMagic]

The thing is I already suffered from calcium lockup by low pH in two different crops. Using the same soil, one from my zone (Growmix multipro), a mix of perlite, vermiculte, compost and moss peat. Tested de pH: firs crop 4.6-4.8, second crop 4.2-4.6.
Humidity 40-50%, temp 23°C, medium-hard tap water, fertilized with Top-Crop (spanish brand). Lights COB leds white+full spectrum (600w per square meter). Strains from requiem seeds and royal queen seeds.
Also, and I don't know if its important, lights were off very often for multiple blackouts in the area. The timers got delayed as well.
I've been using this brand for almost 3 years and nothing happened before...
What do you all think?

The problem is the Growmix Multipro.

Acccording to their website, their pH should already be way too low for organic or even hydro growing:

-pH:5.2-5.8
-Can be used in a wide range of crops. Ideal for cuttings, vegetation and flora

Growmix Multipro 80L

kaizengrowshop.com

Add acidic nutrients, and you can end up with a pH in the 4s, which is is the same as anaerobic fermentation (wine, vinegar).

One thing to rescue this would be to add at least 1 tablespoon per gallon of Maerl or magnesium lime. This should raise the pH for a while. If the mix is this acidic, I'd use 2 tablespoons. Then wet and soak the medium in a tub for at least a few days.

However the key in the future is to start with a medium and nutrients from brands that specialize in cannabis - Canna, Plagron, Biobizz for instance.

 

[Creeperpark]

The problem with cannabis plants is that they can only absorb nutrients within a narrow pH window, which ranges from 6–7 when grown on soil. If the pH is too low or too high, the plant will not be able to absorb nutrients, even if they are there. As a result of "nutrient lockout," nutritional deficits are exacerbated. The pH of the substrate is crucial in plant nutrition because it directly affects nutrient availability. Substrate pH levels below 5.0 increase micronutrient availability, which can result in iron (Fe) or manganese (Mn) toxicity, or both.

I used to think the same thing about pH. However, it really depends on substrate conditionality when it comes to pH numbers. I think his problem comes from using too much peat moss in his mix. The only time one should add peat moss to a substrate is when the substrate is alkaline. If you add peat to an already acidic substrate it will drop too low like above.

The problem with using a lot of lime for a buffer is that when the plant gets over-watered the plant leaves will bronze because the plant can't transpire all the calcium out of the stomata and it gets stuck in the leaves. .

I'm growing in a substrate now that is in the 5s pH and a ppm that's in the 4000 or above 6.9 EC. Also giving this substrate 5.5 pH water to the same plants. So saying plants can only absorb nutrients between 6 and 7 is inaccurate. It depends on the substrate! Thank you sharing friend.

 

[Three Berries]

I've been buffering my water with MgCO3. It only reacts with acid as it is insoluble in water. It has brought the persistently low pH numbers up into the low 6s.

But I'm circling back to a 3 cup to a gallon well/rain and adding a 1/2 a gram of the MgCO3 to that.

 

[Switcher56]

The problem is the Growmix Multipro.

Acccording to their website, their pH should already be way too low for organic or even hydro growing:




Add acidic nutrients, and you can end up with a pH in the 4s, which is is the same as anaerobic fermentation (wine, vinegar).

One thing to rescue this would be to add at least 1 tablespoon per gallon of Maerl or magnesium lime. This should raise the pH for a while. If the mix is this acidic, I'd use 2 tablespoons. Then wet and soak the medium in a tub for at least a few days.

However the key in the future is to start with a medium and nutrients from brands that specialize in cannabis - Canna, Plagron, Biobizz for instance.

I have been using HP Promix since we turned legal. I was recommended that to start along with GHO. GHO was garbage AFAIC (it created issues). I switched to Remo (@recommended dosage) and my girls haven't missed a beat. I augment the perlite by 25%, use measured amounts of H2O every 3rd day, once is a feed the other is water. W D D F D D W. 3gal cloth pots but closer to 5gal (size wise). Outside of soil, VPD is an important player often overlooked

 

[Hammerhead]

You can fix your soil PH by adding lime to buffer it. Shoot for a PH of 5.8-6. Just make sure not to add too much. All mixes use Lime. If it had none that is the issue. It could also have been not enough to fix other acidic inputs. I've been using Promix HP for many years. I've never had any issues using it. It has a base PH of 5.8. I feed with a ph of 6.4. Nothing but happy/healthy plants.


I agree it depends on your medium to know what PH is best. COCO/hydro uses a much lower PH than soils/soilless like promix..

 

[Three Berries]

My issue is using peat starter mix in 16oz cups and not adding any buffer. I think a lot of soil mixes are expected to be used with hard water? Which would buffer the pH up over time.

 

[Switcher56]

You can fix your soil PH by adding lime to buffer it. Shoot for a PH of 5.8-6. Just make sure not to add too much. All mixes use Lime. If it had none that is the issue. It could also have been not enough to fix other acidic inputs. I've been using Promix HP for many years. I've never had any issues using it. It has a base PH of 5.8. I feed with a ph of 6.4. Nothing but happy/healthy plants.


I agree it depends on your medium to know what PH is best. COCO/hydro uses a much lower PH than soils/soilless like promix..

same here