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.