Need Guidance on Ph issue

[GodBud]

Quoted from Site

Adjusting pH Of Marijuana Grown In Soil

A good way to stabilize soil is to use dolomite lime (calcium-magnesium carbonate). Dolomitic lime acts slowly and continuously, so soil will remain pH stable for a few months.
Using fine size dolomite lime is important, coarser grades can take a year or longer to work. You can find fine size dolomite lime at any well stocked garden supply center.


Dolomite lime has been used by gardeners as a pH stabilizer for many years. It has a pH that is neutral (7.0). When added to soil in the correct proportions, it will stabilize soil at a pH near 7.0.

When growing in containers, add one cup of fine dolomite lime to each cubic foot of soil. Mix the dry soil thoroughly with the dolomite lime, then lightly water it. After watering, re-mix it and wait for a day or two before checking the pH. When growing in an outdoor garden, follow the dolomite lime manufacturers instructions.

Lowering soil pH: small amounts of composted leaves, cottonseed meal, or peat moss will lower the pH of soil.

Raising soil pH: small amounts of hardwood ashes or crushed oyster/egg shells will help to raise the soil pH. Hydrated lime can also be used to raise the pH of soil. In containers, use no more than 1/8 cup of hydrated lime per cubic foot of soil (per application). Mix it into warm water, then apply the water to the soil. When growing in an outdoor garden, follow the manufacturers instructions.


Wait at least a day or two before checking the pH level of soil after attempting to raise, lower or stabilize it. If adjustments still have to be made, use small amounts of whatever material you are using. Don't try to adjust the pH more than 0.1 every two days.



My situation



I have tested my Ph runoff and its very low. I used a digital meter and some strips and the meter says 4.3 and the color of the runoff after adding the Ph solution at 4 drops shows the color to be lighter than the 6 via the color chart. So I am thinking that the Ph is in the mid 4s

I have a 3 gal pot using promix bx soiless medium. I am using Canna Terra Flora 2 2 4 and I am in week 5 flowering. From the top down the leaves just around the cola have burnt goldish edges and then there are a few fan leaves below that with same symptoms. Everything below that all leaves look good and healthy.

Temps are 82 Degrees F Humidity is 60% Using 400W HPS

Based off the info on the site I thought it was heat stress but went ahead and did a ph runoff test and found that the ph is low. Now this is assuming my digital meter is right. I have had it for a few years and havent had it calibrated but I dont know a good way to test it so I bought the strips but as stated they both seem to be pointing the same direction that its low and not in the prime zone. So this could be a lockout issue.

I want to get the Dolomite Lime or Hydrated Lime but I am not sure how much to apply. It has been stated Use 1/8 cup of Lime per cubic foot but I dont know if I have a cubic foot of soil in my 3 gal container. I guess what I am asking is how much Lime would you add to a 3 gal container. Its not completely filled to the top but definitely 3/4 or better. It is stated to mix with warm water and apply to soil, can you add nutes during this application? I am assuming that you mix the dolomite in the warm water and test the Ph before adding to the medium is this correct?

It seems to me that the PK amounts on the Canna are low but I used it on my last grow with awesome results. I am thinking this is a lockout issue but makes me wonder why only the top of the plant looks affected. One thing is for certain I know I need to get the Ph in check. I just need a little guidance on how much Dolomite to add based off the size container I have.

Any feedback is greatly appreciated!

Peace

GodBud Reviewed by GodBud on 11-11-2009. Need Guidance on Ph issue Quoted from Site Adjusting pH Of Marijuana Grown In Soil A good way to stabilize soil is to use dolomite lime (calcium-magnesium carbonate). Dolomitic lime acts slowly and continuously, so soil will remain pH stable for a few months. Using fine size dolomite lime is important, coarser grades can take a year or longer to work. You can find fine size dolomite lime at any well stocked garden supply center. Dolomite lime has been used by gardeners as a pH stabilizer for many years. It Rating: 5

[DreadedHermie]

What is the EC (ppm) of your runoff?

I would rather see you flush your soil than get involved with Miss Dola. Do you really want your soil stabilized at 7.0?

If your runoff's hot, that'll give you low pH and lock everything out, which makes your soil get hotter (nutes, I'm talking about) cause nothing's getting used--and it spirals downhill quick.

Just a flush may fix this (?)

[GodBud]

Well I ran 3 gal of RO water through it so I think thats a pretty good flush. So you think I should back off the amount of nutes I am feeding her? Is that what you are saying?

One thing I have checked since the flush is the PH of the feeds I have been giving her. My tap runs about 4 PH. I basically fill a half gal up with tap water then add probably a couple tbs of canna nutes let it set for a few days then pour it in. I could be over feeding. Another thing is when I add the nutes to the tap water it lowers the Ph to about 2.7. So I have basically been feeding this girl a low ph but the promix bx has a built in buffer of lime but I think watering it with a low ph as I have has deminished the buffer. So should I be pouring my feeds with my Ph in the 6.3 to 6.8 range and if so what is recommended to add to the feeds to raise it. Currently I dont have any Ph up. When I did hydro I always had a high ph issue so I got some Sulfuric Acid to keep it in check just a drop or two to the resevoir worked perfectly.

Is there an issue with the Dolomite sounds like you dont like it. Unfortunately I did not take note of the EC/PPM my bad as I have always been used to just keeping the Ph in the prime zone on my soilless grows.

[Zompton]

Sounds like the ph dropped because the low ph of your water, just let the tap water sit out for 24 hours, add the nutes, test ph, adjust the ph to 6.5 and then feed.

[Farmer Rich]

Also, yellowing leaves in week 5 of flowering are not all that uncommon. Part of the plants life cycle.

Zompton has good advice. Also, I've had some luck at the stage you describe with doing a light nutrient flush (400 ppm) at 6.2 - 6.5 ph, then back to your normal schedule when the plant needs watering again. How hot are you mixing your nutrients (ppm) and what ph?

Peace, Farmer Rich

[GodBud]

Ashamed to admit it but I meter tested the ppm of what I had been feeding the girl and it was around 3200. Way hot so the flush was needed. canna has a nutrient calculator and at .5 gal it says ppm should be around 900. So I am sure there are some heavy nutes still in the soil after the flush. Its been 2 days or so so I am going to feed her probably 500 ppm using RO water starting the next day or two. But when I put the nutes in the RO water it drops the Ph and I need something to get it around the mid 6 range before pouring it in. Here are some photos. Any suggestions?

Thanks to all for looking and commenting

[DreadedHermie]

Your tapwater's pH 4.0??? Where do you live--the gates of Hell?

No, wait....that'd be me..... Hermie lives at the Gates of Hell...

If there's a "flushing standard" it's probably 3 gals flush for each gal of pot volume = 9 gallons for a 3 gal pot.

Or, do it the easy way and catch some of the runoff next time you water. Keep watering, and periodically measure the pH and ppm of the runoff as the numbers improve (ppm v , pH ^). When you get the ppm / pH where you want it, you're done! The Perfect Flush. :thumbsup:

I do the last runthrough with a light nute solution as Farmer Rich mentioned. After all, if the nutes have been locked out they've been unusable...

And if you're flushing with RO (or especially distilled) water, remember it's gonna leach out minerals, so you should add calmag on the last rinse or two. (IMO)

I need something to get it around the mid 6 range

That Promix BX is basically peat (acidic) that's been temporarily tamed with lime. It runs 5.5-6.0 like that. If you've exhausted your lime, the peat's gonna start dropping the pH. But if you can get your pH in that 5.5-6 range you should be fine. Just get a little "pH Up" of some kind.

And check the calibration on all your meters. :thumbsup:

[Weezard]

Hermie said;
"Just get a little "pH Up" of some kind. "

I recommend Potasium Bicarbonate.
Can be had from Wine/beer making suppliers.

Aloha.
And 2 cents

Weezard

[GodBud]

Thanks to all of you that have replied!

[GodBud]

Couple more things:

First
Since I just did a flush a few days ago at 3 gal thats way less than the rule of thumb you mentioned at 9. It seems to me, running that much water through a 3 gal pot would water log the roots and cause rot to set in but what do I know. I mean over watering is a symptom right so how do you justify flushing. I would like that explained if possible.

Second

What is a happy PPM on the runoff where is the sweet zone is there a standard for this. Whats considered WAY HOT , Hot ,Medium , and Low. I know where I need my Ph now I want more of an Idea for PPM!

Thanks