Soil run off pH

[mexi420]

Hey guys,

Got a quick question for you. I'm coming to the end of my first 2 plants and I've just done a flush. I decided I may aswell test the run off. Anyway it came out to an even 5.0. Seems way low to me. So just so I don't make the same mistake next time ( if this is a mistake? ) what could be the reason for this. Was I a little heavy on the nutrients? The water I was using was always a constant 6.8 every time so I stopped checking. I know the nutes I was using lowered it to around 5.8 - 6.0. I was running the nutes on every feed at full strength in flower. The plants never developed any visual problems throughout. Organic soil and organic nutes.

 

[Scientific]

Organic soil and organic nutes.

Can you be more specific? What's the pH of unused "organic soil"? What's it made from? If you didn't add anything particularly acidic throughout the grow, then the acid must have been in the soil, no?

Just as an example, I have a tomato on my deck that was potted at the nursery in a mix that looks like it's mostly peat moss, which is well know as an acidic medium. Its runoff is still in the 4s after several washes. I'm guessing that they potted the plant in a way-too-acidic medium because peat moss is cheap and/or because they had a lot of it lying around. It does seem to drain well.

Anyway, your grow went OK, and all's well that ends well, no?

 

[mexi420]

This is the soil.

"Gro Potting Mix 40ltr 100% Organic. A professional peat base mix containing perlite, vermiculte, worm castings, blood and bone and treated with dolomite lime and neem oil"

Yea it went sweet the plants didn't get any problems but I can't help but feeling like i might of been holding them back slightly. Got to squeeze every last bit out of them haha.

Do you guys do plain water every other watering or anything like that? Maybe swap out the nutes for a dose of compost tea every now and then? Or some seaweed extract. As soon as I got the flowering nutes I stopped everything else and just used that. I guess I can only learn from trial and error. I have zero and I mean ZERO experience in plant food haha ...

 

[Scientific]

"peat base mix"

I think that says it right there. Peat is acidic. If you still have some of that soil, could you please put a handful in a pot, add water, and then measure the pH? I'll bet it's quite acidic. (I would be curious to know what result you get.) You said you got good results, and ultimately, that's all that matters, right?

You have probably seen the charts that show which nutrients get taken up by the plant at which pH. You can get around that to some extent by chelating the nutrients and buffering (in hydro), but the organic types probably don't believe in that sort of manipulation of ingredients.

Me, I think organic gardening is fine as long as you don't buy into the magical thinking that goes along with some of it. Feeding plants really does just boil down essentially to chemistry, and where the nutrients come from doesn't really matter--to my way of thinking anyway.

As for skipping feedings for plain water, I go with the orchid growers mantra of "fertilize weakly weekly"--that is, a more or less constant flow of nutrients at the appropriate level is best (again, in my opinion).

And as for knowing zero--we all start there. The good news is that there is TON of info out there now for free.

My suggestion is to jump start the process by copying someone else's successful growth regimen exactly while taking careful measurements and making careful observations and keeping a notebook. That and keeping a grow log here in which you can share your successes and failures and get help from some nice, experienced people (and a few nice, people who don't know anything).

Happy growing!

 

[Scientific]

P.S. The dolomite lime--magnesium carbonate--will neutralize a lot of the acidity of the peat. The question is, how fast will it work? If the peat acids go right into solution and the carbonates don't have enough time to neutralize them, in the short run you're going to have an acidic medium. (Think of putting a piece of chalk in vinegar. Eventually it will dissolve and neutralize the acidity, but it takes a while.)

 

[mexi420]

P.S. The dolomite lime--magnesium carbonate--will neutralize a lot of the acidity of the peat. The question is, how fast will it work? If the peat acids go right into solution and the carbonates don't have enough time to neutralize them, in the short run you're going to have an acidic medium. (Think of putting a piece of chalk in vinegar. Eventually it will dissolve and neutralize the acidity, but it takes a while.)

Hey man sorry for the late reply I'm away for work ATM. Ill do that soil test when I get back because that would be interesting. It will near enough answer my question to a degree. Thanks for all the info it's a real help. Hopefully I can pass it on when i acquire some more experience

 

[Scientific]

Hi Mex -- No hurry.

I watered my tomato with the acidic peat soil again today with pH 9.0 water. The runoff came out of the pot at 4.9. That is some seriously acidic soil! (There are 20 tomatoes on the plant, so apparently it doesn't know that it's supposed to be happier at pH 6).