Soil PH Problems

We are starting our first grow here in Oklahoma, approximately 120-140 autos. I mixed a soil recipe that I had seen on several sites:
3 parts peat moss
3 parts compost
2 parts perlite
1 part vermiculite
After mixing up and getting semi moist and filling fabric pots, it test at a ph of 4. I have added some powdered garden lime, per directions, and I cant get it to raise. I have some wood ash I was told would raise it, but would like some opinions on what my best course of action would be. Havent germinated any seeds yet, wanted to make sure we started off as best as possible. Would like to say in advance, thanks for all your input. Everyone is very helpful here.

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120-140 plants wow that will be a huge grow!!

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And to do such a big grow without previous experience is going to be a huge undertaking.

First I would verify the ph meter is correct and calibrated. Then I’d take a test pot and start pouring 1/4 strength nutes at the proper pH through the pot to see if you can get the effluent to rise to 6.5. It could be the peat is very acidic and the amount of lime wasn’t enough. Also was the lime the soluble type? Hope so because some dolamite lime doesn’t dissolve right away and could throw off your pH as it dissolves through the entire grow.


120-140 daaaahm that’s a lot

Thanks for the reply, Yes on the lime, it was not dolomite. I know it seems like a lot for first time but we just got our growers license and want to try and produce a decent amount of product. I’ve grown outdoors for my self but never anything where I was worried about the plant like I have to now. Would plant a couple seeds and get what I got lol. I kind of wondered if it might be a ph meter issue as well

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That’s why first you need to verify it is calibrated and correct. A grow this size you should be using a professional ph meter and not a $40 meter but you have to start somewhere.

Yeah have a good one on the way, was using one given to me just to check the soil I had mixed. Thanks for your help and any input on using wood ash, good or bad idea?

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You should keep it simple with a basic nute package and you really should think about getting some onsite expertise with growing. The community here can walk you through growing but you have 140 plants…

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I plan to do just that, thanks for your help

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I think wood Ash is good for the flowering phase

Thanks, was just curious because I have access to a large supply

did u send off a sample to a private laboratory for a guaranteed analysis.?
or… r u using a $20 ‘soil pH’ meter.?

with 120+ expensive seeds at stake, i’d either use a known good ‘soil’ or send my custom mix to a lab.!!
some greenhouse supplies have descent container mixes for pretty cheap.!

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Sending ph samples to a certified lab would get mighty expensive and not timely even for professional growers, but a $300+ ph meter and an attachable probe will go a long way to speed the number of samples that will need to be tested. Lots of test tubes and racks that are pre labeled as you test every plant. That’s why many professional growers go with a RDWC set up. Much more control and easy to correct quickly.

Thanks again everybody, by this time next year we should have 4 large greenhouses and everything will be in living soil that we are starting this year. I just saw several post on different site that had this soil recipe as a basic low nute media for autos and thought it would be a simple mix, I have a decent tester but it’s older so have a good one coming. I really think it’s the issue. Thanks again, I love conversing with growers on this site, a lot more helpful and less condescending that others I’ve been on. :+1::+1:

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Is there a lot of nitrogen in your “compost”?

Garden lime will level your pH to around 7, but it takes a while. Sometimes months and months if it’s the pelletized type. Most home made soils need to cook for a while before you can use them.

Peat can also break down over time and lower the pH.

What kind of compost? Store bought? Stuff you composted yourself?

If compost isn’t properly “cooked” it can cause various issues, including acidifying your medium.

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Is there a reason why you are planting that many auto flowers they don’t produce as much and it’s not as strong as photo period due to the ruderalis strain!! You would be able to control when they flower so if you have a problem you can keep them in veg until you can get it where you want it!!

The compost was bought, we are doing our own but won’t be ready for this year. We went with autos, at the advise of other growers, to try and simplify the process for our first run, plan on having both in the future

can’t believe that no one thought of this,
is auto bud even marketable.?

seems like a pretty big seed expense and too many variables in the genetics to be viable for commercial use…???

from what i see on the grow sites Auto’s r not any simpler then photo’s,
sometimes they r actually more aggravating due to the time line of growth.
environmental, gardener, and/or insect damage could be devastating.!

in your situation i would suggest dropping the Auto’s and go with a manageable number of plants to learn the growth patterns and watering methods.!!
maybe start with 10 or 20 photo plants in the greenhouse.!

do u have good-great water pH and EC meters.?

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I am not doing a huge grow like you are, but I have also had concern and issues with PH for my first attempt. I am also sorry if someone mentioned this. I ended up just purchasing a PH up/down pack from Amazon. With that solution, a little goes a LONG way. I am talking 1ml of ph down took a gallon of 7ph water down to about 4.5. so one bottle should last you a LONG time. It was fairly reasonable in price as well. Very easy to test and very easy to correct to make sure you get that 5.5 or 6ph solution.