Persistent Ph problem

[Droopy Dog]

What's the difference between dolomite lime and garden lime, anyone, please?

Some or none AFA difference.

Some garden lime is from a calcitic limestone that has very little Mag in it and is mostly calcium. Still good, you just need to add some epsom salts every now and then.

My bag, from Lowes, says Garden Lime on it and under that says from dolomitic limestone.

Either type of limestone works just fine.

DD

 

[stokesy]

I have two spare plants.. dressed the topsoil with a dessert spoonful of garden lime. Watered with noots, adjusted to 5.8. Initial runoff was around 6.9 ph. After a few soakings, the runoff is now around 7.9. I'll keep watering today, and will come back with the results. But.. it's not looking promising. Almost all my information suggests that lime will increase the ph of the soil. And that seems to be borne out by my findings so far.

The Stoke

 

[Hogdady]

I have two spare plants.. dressed the topsoil with a dessert spoonful of garden lime. Watered with noots, adjusted to 5.8. Initial runoff was around 6.9 ph. After a few soakings, the runoff is now around 7.9. I'll keep watering today, and will come back with the results. But.. it's not looking promising. Almost all my information suggests that lime will increase the ph of the soil. And that seems to be borne out by my findings so far.

The Stoke

Dressing the topsoil is the least efficient way to apply dolomite. It also will take some time before it has any effect.

When you say "Watered with noots, adjusted to 5.8", are you saying that you are watering/feeding with 5.8 ph solution? If so, you should be in the 6.3 to 6.5 range for soil....

 

[stokesy]

I appreciate what you say about watering with 6.3/6.5 - but I'm watering with 5.8 - and I'm now getting readings way in excess of 7 .like 7.3 at the moment. So - watering with 6.3/6.5 would aggravate the situation even more...keep in mind the initial runoff was 6.9, and now, it's 7.3.
Think I'm going to have to flush.


The Stoke

 

[Hogdady]

1) The initial runoff is what get your soil ph from, not subsequent runoff measurements.

2) You should not alter your feed solution ph to affect soil ph. Feed solution should be 6.3 to 6.5. If you need to alter the soil ph, re-read this >>>How Can I Raise or Lower the pH of my Soil Mix?

 

[stokesy]

There are several questions I'd like the answer to, so let me take it one at a time.

Runoff. It's generally accepted that the first runoff is the most accurate, regarding soil ph.

Why should that be? It seems to me, if the soil is more or less dried out (as recommended in many places), then the initial watering will find its way through the air pockets , down through the base of the pot and out. Hardly touching the sides, it seems.
Let's take my last watering, for example. previous ph of the soil, after dedicated watering with 5.8ph was 6.5. I watered with 5.8, after adding the lime, forked into the top layer.And the ph runoff was 6.9. Continued watering with 5.8 has seen the runoff rise to 8.1, 8.2.
How does this make sense?
And, yes, Hogdady, I've read what you recommend... And I;ve seen pics of your first grow - so I take what you say as good info. But I do need an explanation for the rising ph... in these two spare plants...

Tks

The Stoke

 

[Hogdady]

Runoff. It's generally accepted that the first runoff is the most accurate, regarding soil ph. Why should that be?

This is the way I understand it. When the soil is dry and you add water, the soil will alter the water ph to mirror the soil ph. As you continue to add water, the soil will give up less of it's ph as it becomes saturated. Thus, the first amount of runoff is the closest to the actual soil ph.

And, yes, Hogdady, I've read what you recommend... And I;ve seen pics of your first grow - so I take what you say as good info. But I do need an explanation for the rising ph... in these two spare plants...

Tks

The Stoke

What did the tutorial say about raising your soil's ph?

 

[stokesy]

Hogdady, thanks for the runoff answer.. Ok, it makes some sense...As for the addition of lime as an all round stabiliser, as suggested by another contributor...I think, looking at the rising ph....that it doesn't really look that way at all...does it?

Thanks again Hogdady, for sticking it to me again!

Flushing, next..... Change of soil....

 

[Hogdady]

Hogdady, thanks for the runoff answer.. Ok, it makes some sense...As for the addition of lime as an all round stabiliser, as suggested by another contributor...I think, looking at the rising ph....that it doesn't really look that way at all...does it?

Thanks again Hogdady, for sticking it to me again!

Flushing, next..... Change of soil....

I think that you are premature in your assesment of the lime in your soil. As I said, top dressing is the least efficient way to add dolomite and it takes several watering cycles before it starts to take effect. I would highly recommend that you mix dolomite into your soil mix for every grow!

As for your existing condition and per the tutorial, peat moss is an excellant way to treat alkaline soils.

Lowering soil pH: (to make it more acidic)
If your soil needs to be more acidic, sawdust, composted leaves, wood chips, cottonseed meal, leaf mold and especially peat moss, will lower the soil pH.

 

[Fuzzy Duck]

It may be something you have used in you soil mix, i believe you did add vermiculite which has a PH value of 7 some poeple may call that nuetral but is pushing alkline, this may ultimately effect you run off PH !

May i suggest not using vermiculite in a soil mix ? and experiment with run off in a pot with out it !


Just my 2 cents worth

 

[SteveHman]

It may be something you have used in you soil mix, i believe you did add vermiculite which has a PH value of 7 some poeple may call that nuetral but is pushing alkline, this may ultimately effect you run off PH !

May i suggest not using vermiculite in a soil mix ? and experiment with run off in a pot with out it !


Just my 2 cents worth

The people who call a pH of 7 neutral are called scientists. Tell me how that is pushing alkaline? Compared to a pH of 9.0 it would be considered by some to be pushing acidic. But in fact 7.0 is neutral. Also, vermiculite may fall into the range of 6~9 pH. This is one of the reasons most sources recommend adding dolomite lime to the soil mix to buffer any pH swings.

 

[Fuzzy Duck]

The people who call a pH of 7 neutral are called scientists. Tell me how that is pushing alkaline? Compared to a pH of 9.0 it would be considered by some to be pushing acidic. But in fact 7.0 is neutral. Also, vermiculite may fall into the range of 6~9 pH. This is one of the reasons most sources recommend adding dolomite lime to the soil mix to buffer any pH swings.

Maybe saying ph 7 was pushing alkline was a tad bit heavy handed... but going a point or 2 over is pushing alkline tho, in that general direction.

Prehaps you may care to tell us what Ph value of dolomite lime is ?

 

[SteveHman]

7.0 which is why it's used as a buffer

 

[Fuzzy Duck]

Thank you for clarifying the PH value of dolomite lime & we can all see why its used as a stabilizer


But i do believe the origanil poster was quizing about why he had a high ph value of run off pushing alkline in some case's in his posts.

I suggested it might of been a substance he used with his soil mix (vercumilite) ultimately effecting run off ph value ? e.g a suggestion, i don't know the answer so a suggestion was made.

Would we not all be better off knowing what the cause of raised ph is ? for all our benifit 'n' shared knowledge ?

 

[SteveHman]

If you go back and read the whole thread, I don't think we will ever know why his pH was an issue. It could be a range of things and we never got to the cause but were only treating the symptoms. I agree with you that if we can find the cause of the issue it makes treating it much more effective. For example, if he had a high anaerobic bacteria count or pythium both could mess with pH but would have a different treatment than adding a buffer, or pH down.

I think it all goes back to the basic gardening fundamentals, aeration, good soil/hydro follow a sound nutrient plan, and plenty of light and air movement. If you follow the basics, you will rarely have major issues.

 

[spice]

agreed.....OP had high ph because the acidity had been dealt with and there was more than enough lime to do it.....

limestone/dolomite is calcium/magnesium carbonate, the calcium and magnesium are metals and have ZERO to do with the ph. ZERO. The carbonate ion is what neutralizes ph, and it does this by reacting with ACIDS. Said acids are produced, optimally, by the soil bacteria. Typically, they are acetic in nature. High school science says that when carbonate ion reacts with acetic acid you get CO2 as a by product.

To complicate matters, CO2 in water becomes acidic AGAIN (this is what happens in the oceans, they absorb CO2)

soil shouldnt be watered with ph below 6 water, thats too acidic....

Its been my experience that well put together soil mix needs no checking. Use dolomite/ag lime when assembling the soil.....I use tap water when its done like that, no issues

 

[spice]

(edit:double post-damn phone)

 

[stokesy]

I'm a few grows on now. And the problem is now even WORSE!
Using:
Airpots
Barneys Honey B (Sativa)

started with 9 plants, and they're all doing well.. used a 250 watt CFL for the first 6 weeks, so they seem a bit slower than when I used HPS.
Soil.. started off with Biobizz Light mix/Vermiculite/Peat moss from seed to 7 weeks, Transplanted into Biobizz All-Mix/vermiculite/Peat moss plus lime..

3 parts allmix. 2 parts Verm, 1 part Peat, and 1 tablespoon lime to 10 litres of the overall mix.

After transplanting, the run-off was spot on - 6.5

Now, two weeks on, it's up to 7.00 to 7.3.
All that's changed since the last grow is the addition of peat and lime.. which (I think) should make the run-off LOWER.?

I'm only using 1/2 ml per litre of Biobizz Root Juice ..which is half the recommended dose according to the Biobizz chart.
The Ph was brought up to 6.4, prior to watering.

That answers some of the questions raised since I last posted... but I still have the problem.

Any ideas? I'm about to put them into flower, and bigger pots... so I REALLY want to get this fixed before I switch to 12/12

Incidentally, I forgot.. I always add Black Strap Molasses, at the rate of two very large tablespoons to 40 litres of water...

 

[stokesy]

I think I may have discovered the cause of the high pH.

Look at this..

Just chopped the smallest of the group... very low weight.. That's 10 weeks, and the others are still not ready.

All of my grows have been hit by runaway high pH, winding up at 7.2 and higher..

Yesterday, I discovered something interesting. Very interesting indeed... and I'm looking here for an nswer, although, I'm going to post this as a new thread..(this is the thread I'm talking about)

On my first grow, I was using cheap ph meter.. which became inaccurate fairly quickly.... so, for my second grow, I bought a Bluelab pH meter. Just the single meter - it was expensive, but I like to get things right, and detest things that don't work....

I've used it ever since, rarely requires calibrating... seemed to be working perfectly. Checked it with the requisite buffers.

However, I use rainwater, with the ph adjusted, usually with lemon juice, or vinegar. So.. I'd pull the rainwater, check the ph, add the noots, then adjust the solution to 6.5. All the time, I have a bubbler working, to help the solutions merge..

Then, I water.

Now, I've discovered, that the Bluelab meter, starting at ph 4.00, when in the solution, takes the following time in minutes to stabilise.zero 4.00

I used just plain rainwater for this little test. I thought It may have been a temperature change or similar, but it seems not.
2 mins 6.1
5 6.2
21 6.4
32 6.6
43 7.00
55 7.10
63 7.10
73 7.00
83 7.00
120 7.10

I'll go with 7.1 being the most accurate.

So... that's 55 MINUTES to read the correct ph. Is that RIGHT?
I've been giving it about 10 minutes to stabilize..which means that when I thought I was watering at 6.2 or 6.3, in actual fact, I've been dosing it with 7.1 !!

Now.. anyone else have any experience with the Bluelab ph meter?

So... the rise from 4.0 to 7.1 is about an hour. When the probe is replaced, rinsed, and returned to the 4ph buffer solution, it reads 4.00 in about 10 seconds.

Is it a faulty meter, do you think?

 

[stokesy]

Just checked the probe again, but this time taking it from 4.00 to 10.00 (milk of Magnesia).

After 20 seconds, it read 9.7. Now, after a total of 35 secs, it read 9.8. After 2 minutes 9.9. So. Nothing wrong with the probe when it's looking at a BIG swing up, at least.

Still doesn't resolve my query, just adds another little piece...

So - if the probe is working (correctly?), the problem must lie with the solution. Which is fresh rainwater. So.. it follows that there's something in the rainwater (nitrogen, perhaps?) that's inhibiting the meter readings. And that inhibition appears to break down, as time passes. Now.. the probe must work on the send/receive signal, presumable, which is electric. When water is absolutely pure, as I recall, it acts like an insulator. Could be the other way round, but I think I'm right... So.. how would a meter work with distilled, or de-ionised water, I wonder.. Thats' my next test.