Need some help with a ph question in promix

[Purple Goose]

I have been growing in promix bx with myocorrhizae and my plants are looking very healthy and growing quickly but I have read that ph for soil's sweet spot for ph is 6.5 and hydro is around 5.8 but the thing is I have been watering and feeding with a solution ph'd to 6.3 the promix has a ph of around 6.2 and I added 1 cup of dolomite lime per cubic foot but from the very begining my runoff ph is always around 6.1 or 6.2 in every pot so what I am wondering is if this is normal for promix as I know it isnt trully a soil in fact is considered soilless mixture so would a ph of 6.0 in the root zone which is what It appears I have.

So even though I see no problems with my plants no yellowing no leaf curling no deficiencies and growth is pretty damn good as plants are between 25-32 days old from seed and between 10-14" tall but have all be extensively lst'd so there are multiple tops on all of them some having up to 8 tips all at the same height.

Here is an example of how they all look some of my white widows I did give a very minor nute burn but nothing at all serious.

So with this example would you think I should change anything in what I am doing presently as this plant is 26 days old and is 13" tall with about 7 branches all about the same height . And just wondering if anyone would have any idea if I were to flower it right now would this yield over an 1 ounce under a 1khps do you think or should I give it another week or so veg?

 

[Droopy Dog]

Looking good.

If you hadn't added that lime, your runoff would be much, much lower than it is. Peat based mixes are pretty acidic and so are most nutes.

Even though it is soilless, I like my runoff a bit higher, closer to 6.5. 6.1-6.2 is getting close to lockout low.

Since it does get consumed by the plant and you are getting ready to flower, perhaps top dress with more lime, like 1-2 tsp/gallon of mix? Not much, but a little to raise the pH just a touch.

All in all though it's looking good.

DD

 

[Purple Goose]

Looking good.

If you hadn't added that lime, your runoff would be much, much lower than it is. Peat based mixes are pretty acidic and so are most nutes.

Even though it is soilless, I like my runoff a bit higher, closer to 6.5. 6.1-6.2 is getting close to lockout low.

Since it does get consumed by the plant and you are getting ready to flower, perhaps top dress with more lime, like 1-2 tsp/gallon of mix? Not much, but a little to raise the pH just a touch.

All in all though it's looking good.

DD

okay well I have to transfer them anyways to 3 gall pot before flowering as tghey are in 1 gall so will amend the 3cuf of promix with 3-4cups of dolomite abd then transplant that should take care of adding more lime to the soil

 

[Droopy Dog]

okay well I have to transfer them anyways to 3 gall pot before flowering as tghey are in 1 gall so will amend the 3cuf of promix with 3-4cups of dolomite abd then transplant that should take care of adding more lime to the soil

This 3cf of PM hasn't been already limed has it?

I mean, I wouldn't add 3-4 cups of lime to mix that already had 3 or so cups of lime in it.

But now that you know what kind of runoff you get with 1cup/cf, you can adjust the amount of lime to the next batch.

That's what it's all about, doing and observing and then adjusting to fit your particular grow/situation.

DD

 

[Purple Goose]

Oh no just a new bag I originally added 1cup per cubic foot and runoff is around 6.1-6.2 so going to increase to 1 1/3 cups per cuf but I found by watering with nute solution at 6.6 instead of 6.3 I get runoff of 6.4-6.5 so I figured if I increase my dolomite by 30% then I should be able to rreturn to about 6.2 6.3 on my ingoing nute sound about right?

 

[Droopy Dog]

Oh no just a new bag I originally added 1cup per cubic foot and runoff is around 6.1-6.2 so going to increase to 1 1/3 cups per cuf but I found by watering with nute solution at 6.6 instead of 6.3 I get runoff of 6.4-6.5 so I figured if I increase my dolomite by 30% then I should be able to rreturn to about 6.2 6.3 on my ingoing nute sound about right?

Sounds like a plan. Observation and refinement.

I also run a bit more than a cup/cf, but didn't start out at that amount.

DD

 

[Purple Goose]

Actually I think if my calculations are right and the info on the promix is correct off there pdf about it this calculation should work pretty good.

The promix is ph's to 6.2 after adding in 1cup dolomite per cuf and watering for 6 weeks at 6.3 and having runoff at 6.3 it has now drifted to 6.1 6.2 so this would suggest that the buffering capability of the 1 cup of dolomite I added has been reached so I wouldnt be surprised if the buffering capability of the promix is about equal so maybe when I transplant i should stick to the same mix of 1cup per cuf as it will only need to be able to buffer the ph for another 8-10 weeks which should be no problem considering the natural ph of the promix as well and if it drifts a bit low at the end then I can just increase my ingoing solution to compensate anyways better to stick to something that appears to be working according to the rules as I understand them considering the ph buffering capability of soil .

Oh and also the picture above I said was at day 26 that was a typo meant day 36

 

[Droopy Dog]

A new member made a good point in your other thread and that is, a compressed 3.8cf bale expands to ~7cf.

You should measure your lime to the expanded amounts, not the compressed, so, closer to 7 cups of lime for the entire bale.

I never thought to mention it because I normally just mix up 2cf at the time. This is the amount I can do in my wheelbarrow.

If you were adding lime to the compressed amount (3.8cf), this might explain your somewhat low runoff pH.

DD

 

[Purple Goose]

I am pretty sure I added a total of 6 cups actually think it would be good to top dress the 3 gal pots with a couple of tbl spoons of dolomite to make sure as far as I can figure I dont think I am even close to overdoing the dolomite I also think my runoff might be a bit lower then it should be as I am setting my nutes to 6.2-6.3 when I water but I am not just collecting the first 10 seconds of runoff instead I measure the entire runoff of about 20% and measure that I was told this will give me a more acurate idea of waht the ph is in the root zone .

 

[Droopy Dog]

Sounds good.

The way I measure runoff is to water well with a good runoff, toss all this. Let the plant sit of 1/2 hr or so and then add just enough water to snag some runoff and test that.

It's all good. Way Mo Betta than playing guess the pH.

DD