Acidic Soil

[FrisbeeHead]

Hi there,

I'm half way through flower and I'm having problems. My run off water has a pH of 4.9-5.1!!!

How long has this problem been going on? 2-3 weeks
What STRAIN are you growing? 3 Hashberry (mostly affected, see pics) + 1 Kalichakra (doing pretty good)
What was the establishing technique? (seed or clone?) Seed
What is the age of your plants? 7 weeks in flower (+25 days veg)
How long have they been in the soil mixture they are in now? 7 weeks
How Tall are the plants? 70-80cm
What PHASE (seedling, vegetative or flower) are the plants in? Flower
What size pots are you using? (Include how many subjects to pot) 11liter (if you mean how many plants to 1 pot, it's 1 plant/pot)
What substrate/medium are you using? What brand of soil mixture are you using?(percentage of perlite, vermiculite...etc?) Professional soilmix (nothing added)
What Nutrient's are you using? BioCanna's BioFlores
How much of each nutrient are you using with how much water? *Knowing the brand is very helpful* I've only fed plants 2 times with nutes. First time was 40ml/10liter of water about 2 weeks ago and 20ml/10liter of water 1 week ago
How often are you feeding? I've stopped feeding until pH is back to normal
If flowering, when did you switch over to using Bloom nutrients? Went on 3 weeks without nutes then I started.
What is the pH of the "RUN-OFF"? 4.9-5.2 (!!!)
What method of pH test was administered? Using Strips? pH pen? Pen (Adwa AD-100)
How often are you watering? Every 3-4 days
When was your last feeding and how often are you feeding? 1 week ago
What size bulb are you using? 400W HPS
What is the distance to the canopy? 20-30cm
What is your RH Factor? (Relative Humidity) 35-40%
What is the canopy temperature? 25-28C
What is the Day/Night Temp? (Include fluctuation range) Unknown, but I guess it drops 5-10C at night
Tell us about your ventilation, intake exhaust and when its running and not running ? Exhaust (355 m³/h) running 24/7
Is the fan blowing directly at plants? Yes I have a fan blowing at the plants as well. I turn it off during night time (noisy)
Is the grow substrate constantly wet or moist? No, I pretty much let it dry out before I water
Is your water HARD or SOFT? Unknown but it's drinkable tap water and it has a pH of 7.5 and I adjust it with ascorbic acid to 6.8 (before that I used vinegar)
What water are you using? Reverse Osmosis (RO)? Tap? Bottled? Well water? Distilled? Mineral Water? Tap
Are you using water from a water softener? No
Has plant been recently pruned, cloned or pinched? No
Have any pest chemicals been used? If so what and when? No
Are plant's infected with pest's? No

With that said, this is how my plants look:

As the newbie I am I initially thought it was strictly a nutrient deficiency so a couple of days after the plants started to look like the above pictures I added BioFlores (organic nutes), a 40ml/10liter solution. A week after that 20ml/10liter. Then I got some help on another forum and I realized nutes wouldn't do it, because I had a pH problem. Since I've been measuring my water every time I water with a pH-pen (calibrated) I didn't think that I could have a pH-problem, but when I measured my run-off water it was pretty obvious... 4.8-5.2!!!

This is what I have done so far:

- I flushed one plant with a ratio of 5:1 (pH 7.0). Didn't help. (Well it did go up from 5.1-5.3, but that could have been the pH-pen's fault)

- I removed the top layer of soil on all plants, gave them a good water and added fine-grained dolomite lime (5 tea spoons) on the surface and then I put back the top layer and gave them a good water again. Measured the run-off next time I watered them, still 4.9-5.1

- Recently I added dolomite lime again (5 tea spoons), but this time I mixed it with the top layer before putting it back. I will just have to wait and see if this helps. I'm afraid it doesn't penetrate the soil enough?


I have about 30 days left of flowering and with this problem I really can't do much. I can't add nutrients and I'm worried my harvest will be minimalized although buds seem to grow pretty good for the time being.

I haven't tried hydrated dolomite lime (to mix with water) yet because I haven't looked around for it, thought the fine-grained would do it.

So what do you think? What can I do to restore my soil back to normal. Every input is appreciated.

I would also like to thank MynameStitch for the excellent Guide!

 

[PazVerdeRadical]

Is the grow substrate constantly wet or moist? No, I pretty much let it dry out before I water

Is your water HARD or SOFT? Unknown but it's drinkable tap water and it has a pH of 7.5 and I adjust it with ascorbic acid to 6.8 (before that I used vinegar)

hello man,

vinegar has the ability to stick to the soil, it is hard to flush it in other words. fixing your water's pH with it may have caused you the acidic pH you are now experiencing. also, do you know how your ferts react to the vinegar? I don't, but I am sure something goes on, but what?

also, letting your soil dry out too much will affect your pH as well, specially if you have been using vinegar as well as non-organic ferts.

you should flush your plants with alkaline water, your tap water is already alkaline, and you have already added lime, perhaps add more lime and water a bit more without adjusting the pH, there is not much else you can do this far into flower.

good luck!

paz y salud

 

[FrisbeeHead]

thanks for the reply paz,

when i add ferts to the water i don't use vinegar because the ferts adjust the pH.

i'm using vinegar because this is recommended by mandala.com.


as you point out i think i have had a bad watering schedule, letting the soil dry out to much and watering with high amounts of water... maybe this in combination with the vinegar has made the soil acidic.

i will measure my run-off once again in a couple of days and if it's still low i will flush with tap water (mixed with dolomite lime) and just hope for the best.

i got a little less then a month to harvest and buds look pretty nice so it's not a total failure.

once again, thanks for the input,
take care!


if anyone has more recommendations on raising pH in soil when in flower, feel free to drop them here

 

[PazVerdeRadical]

hello again Frisbee,

a better way to lower the pH of water would be using coffee, save left-over coffee and/or used coffee grind. smells nicer than vinegar and flushes a lot easier.

your plan sounds good

good luck

peace

 

[Darkstarlive]

Your plants are in need of Phosphorus.
http://www.growfaq.net/growfaq/97.htm

Good luck

 

[10k]

Thorough flushing and the watering through with dolomite lime should have solved the problem, but seeing that your pH isnt going up even though you've given alot of dolomite lime and watered through, I have a feeling your root system may be diseased, beginning to rot within the soil.

Can you carefully pop the entire soil plug out of the worst looking of the three and show us a picture of the roots ?