About pH imbalance : it’s near a cataclysm but the culprit seems to be…
11:13 pm in Nutrients, Plants, Seeking Advice by Louise from Quebec
Hi again !
The situation didn’t improve in my clay pot windowfarm since my last post.
The oddest thing is happening : when I take water samples from under each pot of a column, the further down I go, the higher the pH reading.
pH readings took within half an hour from :
inside the upper reservoir : 5,5
at the end of the drip tube : 5,5
under the 1st clay pot (the highest) : 6,5
under the 2nd clay pot : 7,5
under the 3rd clay pot : 8
under the 4th clay pot : 8,5
under the drain tube (after the 5th pot) : 8,5+
and just to make sure : a second, double-check reading of my water source in the upper reservoir : 5,5 !!!
Then, I tested one empty spare pot for pH neutrality by plunging it in water for the night : water pH remained the same.
I tested the pellets : no change (and no surprise) there either.
The only thing left was the rock wool : Bingo ! I found the only culprit. In the 4th clay pot, the water extracted from the wool had a very high pH. Since the poor plants are dying anyway, I drenched the whole pot and its contents with 1 litre of acidic water (pH 5). Then I let it sit to dry for the night and this morning, the pH of the water retained by the wool was 7+.
Is it possible that an agent of some kind took residence inside the wool, reacting chemically with the water and-or nutrient liquid to pitch the pH repetitively up ? Or would it be that the water previously absorbed by the wool would be locked there and couldn’t be diluted by the newly coming fluid, this fluid dripping right through with no or almost no effect ? No, this last theory doesn’t work, because if it were the case, the pH in my bottom reservoir would still be around 5,5.
The simple fact is : even after letting more than 10 litres of acidic nutrient solution (pH 6 or below) pass down through my column over the last week or so, all this water had turned to a pH of well over 8. Therefore, a chemical reaction is occuring during the descent.
I have this problem of raising pH from the day I started monitoring my pH. What would start at 6 would end down around 7 or 7,5. During the installation of my plants, I innoculated my rock wool cubes by dipping a whole batch of them in Eco Root Dip Gel which contains 16 different mycorhizal fungy. I didn’t use them all the same day and some sat in the solution for several days before I used them. As after a few weeks my plants didn’t grow much or didn’t grow à al in some cases, I added my filtered urine in the mix in the hopes of raising the nitrogen contains. From that point, the pH went wild and very high. From Britta’s explanation on the use of human urine as a nutrient, it would be normal for it to affect the pH in that way while it would break into ammonia.
But my system is litres away from that mixture. By that time, I would have expected it to recover, at least partially.
Does anybody have an explanation ?
I’m planning to replace my pots one by one, taking out the bottom ones first (4th ones, which are plagued with the highest pH of all), emptying and desinfecting it, and reinstalling a new plant in it as my new seedlings sprout. Then, pot number 3 would move down one level, replacing pot number 4, number 2 and one following this descent. Pot number 4, newly filled up, would move up high in the column, safe from infection, because no old pot would stand over it to drip in it.
I would slowly replace everything in that fashion and of course, I would never reuse the water from the bottom reservoir until the end of the process.
Any insight highly appreciated. And I’d like Britta’s point of vue on this. So… @britta
By the way, my affected plants are wilting and then shrivel slowly. The peas that are in the upper levels look healthy. The only plants I got out from their pot are my most affected peas. They are shriveling but their root system is developped and looks very healthy, with no sign of rot or damage whatsoever. No slime and sign of pests either. The wool rock is clean and evenly moist, just as the roots.
Are your clay pots glazed or anything like that?
I’d run a test with the pots empty to see if they are affecting the water in any way.
You also might have too much rockwool. I’d do small cubes for your next plants. You don’t need very much to start off.
Avoid using urine for the time being. Just use nutrient fluid, and swap it out on a weekly basis.
Hello, Hardware Junkie,
Yes, my clay pots are glazed and I did exactly what you suggests because I was suspicious of them. But they passed the test easily, just like the hydroton.
I’ll follow your suggestion and put less rockwool, next time, although the roots didn’t suffer any damage from excess moisture. And as soon as I saw the bad reaction of my plants I stopped urine over a week ago and rinced my columns with acidic water. I bought an organic nutrient, Iguana Juice, and I will use it as the main source of nutrients, coupled with worm tea as a complement. Thanks for the advice, it comforts me in the correcting moves I began to apply.
I talked to the guy at the hydroponic store and to his boss. Both don’t understand what’s going on. They say that usually, pH imbalances tend towards acidifying. They never saw the opposite phenomenom. I’m supposed to call them back monday, as they’ll try to get advice from someone more experienced.
In the meantime, I’m not depressed. Intellectually, it is stimulating, at least for now ! LOL
I find your situation and interesting one. I have yet to start my own system so I have no experience in this aspect of your problem, but I am a hydrogeologist and have taught environmental systems in high school for years where we have examined the reasons for pH changes in the water cycle within watersheds.
Naturally, rain water (5.5 to 6) infiltrating through soil and rock will become more alkaline (higher pH) the longer it is exposed to soil and rock as it dissolves especially calcium based minerals. So the rock wool is a likely culprit. The question is, what is it made of (mineral content)?
What I find interesting about your experiment is that the problem does not just seem to be in pot 4, but starts in pot 1 and each pot adds 0.5 pH to the reading as it moves down. So it seems likely that there is something in each pot that is adding to the pH…
Another thought that came to mind is that algae living in water photosynthesizing will also naturally make the water alkaline (higher pH) as the algae will draw the CO2 from the water, reducing the amount of carbonic acid in the water, thus increasing the pH this way. I don’t know if this reaction is occuring in hydroponic systems. Likely not, if the plants draw the CO2 through the leaves in the air, but if there are photosynthesizing algae in your system, this could have an impact.
But first look at the make up of your rock wool or clay pots and if there are calcium based mineral such as limestone, calcite or dolomite somewhere in your system, these will dissolve over time and would be increasing the pH.
Good luck
Roland
Hi, Roland,
it seems to me the rock wool or the glazed porcelain pots are not the culprits, since my pH problem is not existing anymore. I didn’t have an algae problem – at least that I was aware of. I changed everything in my pots, the old rock wool having retained something, as I explained earlier. The new rockwool didn’t behave like the previous one.
Now, my pH is very steady, even for a few weeks. So, at the time, the possible culprits left are : the Eco Root Deep Gel, my homemade compost tea (its pH being very high), or another unknow source.
I didn’t come back to worm tea as a nutrient, sadly, and I don’t dare to. I now stick to a bought product, Organic Iguana Juice. The smell is not appealing at all, but otherwise, it’s a good product, though expensive. I tried to produce worm compost that is not alcaline, but didn’t succeed yet. Then my gardening season started outside, and I put all this aside. But maybe this winter, I’ll have time again to experiment again.
As for my dripping system, it’s still working without any pump, only gravity. I have to enameled galvanized metalic tubs, feeding a transparent plastic container. The whole thing contains about 16 litres and if I adjust the dripping rate properly, I can water my plants very evenly and slowly for more than 48 hours without having to readjust the valves (the dripping rate changing with the lowering of water pression as the tubs empty themselves.
Thanks a lot for your comments and hints, though, because it’s new infromation for me. I keep a copy of what you wrote, for further reference.
Hi, Louise,
I’ve just pulled up some information about rock wool and your problem is a known one. Commercial hydroponics uses rock wool, but must balance its pH before use (known as ‘conditioning’). The page linked below suggests soaking the wool in a pH 5-5.5 solution (they don’t say for how long, overnight maybe?) before rinsing in water.
You can pay through the nose for special acid conditioning solutions, but I don’t see why a homemade solution won’t work as well. If you would like suggestions on how to prepare such a solution, leave a reply and I’ll see how much Chemistry I can remember from school.
http://www.guide2hydroponics.com/about-hydroponics/growing-media/rockwool.aspx
Hi, James,
your information is right. We have to balance rock wool’s pH before using it.
I always do it, simply following the instructions on the packaging. About half an hour is sufficient to soak the wool thoroughly and it’s done. I did it with lemon juice and also with white vinegar, as instructed. Rock wool is an inert material and it won’t affect the pH all by itself, but once it is set on a given pH, it seems to keep like that for a good while, in my experience.
Therefore, something else built up inside the rock wool and modified the pH.
Whatever the problem was, though, it never occured again and my nutrient solution is amazingly stable compared to that period in last March. With the comments that I recently received in reply to another article that I wrote on the same subject, I now have another line of thought to pursue : my city treated water could lack minerals which can act as buffers to stabilize the pH. It’s a problem encountered in sea water fish tanks, for instance.
Thanks for the comments, it’s always appreciated !
Merry Christmas !