New Grower PH confusion

[DanteW420]

I understand the formula for figuring out the PH level of my soil by getting a PH reading of the water going in, and comparing it to the run-off...I just can't figure out what i'm supposed to do with that information.

I am preparing a pot for a new grow, using OF/HF/perlite 1:1:1

I PH tested the water before I saturated, and it was at 7.0.....the runoff was 5.45... which tells me that the approximate PH of the soil is only 3.9

Now, does this mean that when I water the next time...I need to add 2.6 (the difference between the current 3.9 and the goal of 6.5) to the 7.0 that I started off with on my last watering?

that almost doesn't even make sense to me lol

also since that is the first water to ever go through the soil...does the ph of the water effect the ph of the soil after you already get a run-off reading.....

maybe im thinking about this too much, but anyways, if anyone has any tips or advice on this, some help would be appreciated

thanx

 

[faded187]

ur gonna have to look into adding lime to ur soil to stable the ph.fox farm soils have been very low ph right out the bag

 

[az2000]

also since that is the first water to ever go through the soil...does the ph of the water effect the ph of the soil after you already get a run-off reading....

First, you're doing the right thing by testing some sample soil before germinating seeds. Considering what your initial test revealed, I'd continue testing. It sounds kinda bad. I'd give it 2-3 days to dry a bit, then water again to test the runoff.

Maybe you'll need to add dolomite lime to your mix. Dump it out, add 2 tbsp/gal, mix thoroughly and put it back in the container, continue testing. Or, maybe it's not a good idea to mix those two soils. (Do you know of anyone else doing it?).

Also, the nutes you use might help. If they're ph balanced they may hold the soil's ph. I believe GH Flora Series has this capability. I think it helped me avoid an acid soil condition that I didn't discover until I changed nutes.

 

[Muddy]

It's getting so that I cringe when I see someone using OF. Their quality control is in the toilet anymore. I would do as AZ suggested. Add 2 tablespoons of dolomite lime per gallon of mix, wet it with water pHed to 6.5 and let it sit for 2 weeks, then water it again and test the run off. The dolomite lime will raise the soil pH but it takes about 2 weeks so don't expect to see any immediate changes.

 

[DanteW420]

Thanks for all the help guys...I did end up getting some lime, of course small town living meant I had to get regular powdered lime and not dolomite....but I dumped the soil out of the pot, added 2 tablespoons of lime, and this time testing my soil ph went up from a 3.9 to a 7.1 which is much more tolerable.

This will also be my first LED grow (I picked up a 180w ufo) and based on other things I have read around the net, I added a little bit of calmag as well...hopefully the calcium in the calmag doesnt cause an issue because of the calcium already in the lime...but will see what happens.

Muddy....do you think it will cause much issue if it doesn't sit for 2 weeks first?

 

[az2000]

Thanks for all the help guys...I did end up getting some lime, of course small town living meant I had to get regular powdered lime and not dolomite....but I dumped the soil out of the pot, added 2 tablespoons of lime, and this time testing my soil ph went up from a 3.9 to a 7.1 which is much more tolerable.

It sounds like you used hydrated lime. That's very different, much stronger, and phytotoxic at modest levels. IMO, 2tpsp is a lot. Most people should avoid it entirely. I'm surprised 2tbsp only took it to 7.1. I would have expected 8.5. For your acidity I would have suggested something like 1/2 - 3/4 tsp per gallon of soil.

You're still going to need dolomite lime. You can order it online. I've used Fertilome Hi-Yield Agricultural Lime. It's the consistency of sand, with a lot of powder too. (You want it as fine as possible.). If you can find "Spartan Speedi-Grow Agricultural Limestone" that's extremely fine. A blend of dolomitic and calcitic lime.

If you're ok with experimenting, you might create 3-4 half-gallon samples and try different doses of hydrated lime to get closer to 6.3.

If you just want to get growing, I think I'd dump that stuff, spend $30 on Pro-Mix HP (or BX if you use HID lighting, it has vermiculite to help it stay damp). Do a half-gal test. I would add 20% perlite and dolomite at 1tbsp/gal soil. Muddy doesn't think it's wise to add dolomite to pro-mix. But, I haven't experienced his higher ph out of the bag. If you do a half-gal test you'll get a feeling for whether you could follow his no-dolomite advice or mine.

I think I'd dump the soil you limed. That's a lot of lime.

 

[DanteW420]

yeah, this is the lime I purchased http://www.fertilome.com/product.aspx?pid=bbdaac90-20dc-4221-97e9-5dc514b71198 ...its hard to find decent supplies around this town

- - - Updated - - -

yeah, this is the lime I purchased http://www.fertilome.com/product.aspx?pid=bbdaac90-20dc-4221-97e9-5dc514b71198 ...its hard to find decent supplies around this town

 

[az2000]

How will you proceed?

How big is your container? You used 6 tsp of hydrated lime. That's a lot. If it's a 5-gal container, maybe 1.2 tsp/gal isn't bad. If it's a 2 gal, I think 3 tsp/gal could create problems for a seedling.

You could flush it and see if it goes down closer to 6. Or, you could dump it and re-lime it with more like 1/2 to 3/4 tsp /gal. Or, move on to a different medium.

Maybe someone else could say how toxic it would be. But, I get the impression nobody uses hydrated lime because it's universally warned against. I used it in small doses to correct a severe mid-grow problem because the alternative looked like a dead plant. It turned out well for me. So... I think the naysayers may be overlooking a useful tool. Maybe you could get a useable soil from your acidic starting point using hydrated lime (and a healthy dose of dolomite lime for longer-term stability). But, I think you overshot it with 2 Tbsp. If you're not worried about losing a seed, give it a shot. Nothing wrong with learning how it will work.

BTW: this is the Hi-Yield Agricultural limestone: http://www.fertilome.com/product.aspx?pid=c77a5268-0126-4707-b4e7-0da0c40283f7

You can compare the analysis of it and what you bought to see the difference. It's much more magnesium.

 

[Muddy]

Sorry, but that is the wrong lime to use. Hydrated lime can be very toxic to the plants, especially at high levels. I only use it in extreme cases where I need to raise the pH quickly, as it's faster acting, and then never more than 1 tablespoon in a 3 gallon pot. At high levels it will also kill the beneficial microbes in your soil. If you have a Lowes or Home Depot in your area they sell dolomite or as it's sometimes called, garden lime. People commonly use it on their lawns or gardens to raise the pH, so it's commonly available.