My pH study has me confused, thoughts?

I have a blackberry kush auto that is looking sickly, so I decided to investigate my soils pH and TDS, I am confused about the results! I used foxed farms ocean forrest, one sample from the bag (unused soil) and one sample from my pot (8 weeks old). I combined 1 part soil to 1 part distilled water (pH 7, 0 ppm), stirred and let sit 24 hours. The soil from the bag had pH of 6.35 and 1250 ppm. The soil from my pot had a pH of 6.45 and 150 ppm.

I have been watering this pot with tap water pH of 7.5 and have fertilized about 7 times (5 veg and 2 bloom). I thought for sure either my soil was too high pH or I had a build up of salts from the fertilizer. It appears neither is the case! Now I don't know what to think, any ideas?? Thanks fellas

What is your runoff ppm? That's a better way to detect salt buildup. But, it's more reliable if you watch it from earlier in the grow to see how it rises.

Usually, soil ph is determined with a good soil probe. (I have the Control Wizard Accurate 8.). Otherwise, measure the runoff. But, you have to collect runoff in a special way. Google for "NCSU Pour-Through Method Runoff". I don't know how that method compares to what you did.

Do you let your soil dry fairly well between waterings?

I wouldn't worry about the ppm of the soil.

Those readings are OK. Remember as soil dries the pH raises. It allows proper nutrient uptake.

The ppms of the soil could be from all kinds of things. I'm not sure what the ppms should be.

az2000 said:

What is your runoff ppm? That's a better way to detect salt buildup. But, it's more reliable if you watch it from earlier in the grow to see how it rises.

Usually, soil ph is determined with a good soil probe. (I have the Control Wizard Accurate 8.). Otherwise, measure the runoff. But, you have to collect runoff in a special way. Google for "NCSU Pour-Through Method Runoff". I don't know how that method compares to what you did.

Do you let your soil dry fairly well between waterings?

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Run off pH means nothing. The probe is better.

The op used distilled water. It actually calls for deionized water.

To be honest I just got the TDS pen and have not checked runoff yet. I assume you want to check the runoff from straight water, no fert right? That pH probe looks nice, I may consider that, although I believe my method should be accurate, just more work. I use air pots and they do get plenty dry bt waterings.

Post a pick. I doubt its a pH problem.
Az meant check the ppms of run off.

AtticGrower002 said:

To be honest I just got the TDS pen and have not checked runoff yet. I assume you want to check the runoff from straight water, no fert right? That pH probe looks nice, I may consider that, although I believe my method should be accurate, just more work. I use air pots and they do get plenty dry bt waterings.

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I feed every watering. I measured runoff ppms each time to determine how much I could feed to not get buildup. I also do significant runoff.

The soil probe is handy to have, but I don't use it much. I'm trying a different fertilizer and it's handy to see if it's acidifying the soil. For example, I don't pH my nutrient solution. I was concerned if that was just a lukcy condition with my nutrients. I was worried this new product might be an unpleasant surprise in that regard. It's nice to be able to check that fairly reliably.

whitebb2727 said:

Run off pH means nothing. The probe is better.

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The Pour-Through method seemed pretty good when I tried it with distilled, which is fairly close to deionized. It's about 0ppm (no ions to measure). For this purpose, it should be satisfactory. But, I agree, the probe is easier to use.

Thanks Az! What exactly do you mean by significant runoff? I am using 3 gallon air pots. I typically give them 1.5 gallons water every 3 days. Its just enough to saturate. How much and how often would you recommend? Also, since you are fertilizing every time do you still use a 1x dose?

AtticGrower002 said:

I may consider that, although I believe my method should be accurate, just more work.

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You should try that Pour-Through method I mentioned, just to see how it compares to what you did. I'm not sure what you did is accurate. It requires reaching equilibrium over a period of time. You may have given it a lot of time, but there may not have been enough soil to affect the water completely. The Pour-Through is maximum soil, minimum dilution.

AtticGrower002 said:

Thanks Az! What exactly do you mean by significant runoff? I am using 3 gallon air pots. I typically give them 1.5 gallons water every 3 days. Its just enough to saturate. How much and how often would you recommend? Also, since you are fertilizing every time do you still use a 1x dose?

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I do about 20% runoff. You don't have to do that. I think it's a good safeguard for a new grower. But, after you dial in your nutrient strength, you could feed with no runoff (in a perfect world). I find my plants prefer a bit more "refresh" than that. So, I feed a little heavy and get some heavy'ish runoff to compensate. (But, it takes 1-2 grows where you watch the PPMs to find that safe strength/runoff combination.).

I never did alternating feed/water/feed. If I did, I'm sure I would feed stronger. I don't see any reason to alternate unless you're feeding organic goodies and want to keep them separate from synthetic nutrients.

I'm actually not a fan of FoxFarm because it seems people guess at when to start feeding. It has always struck me as "nutrients from soil for some number of weeks, then start feeding." It also seems heavy/dense to me. I like a lighter soil. But, it could be a matter of style, not substance. @gardengardian7 speaks of FF as being a system. Maybe he can help you get dialed in. He discussed it in this thread.

I will give the Pour-through a try. If I understand correctly I fully saturate the pots, wait an hour or so, then add an additional 1.5 cups and measure the runoff from that? Am I just using pH'ed water?

You can't pH distilled water because it has no buffers to hold it. Just follow the 1-2-3 instructions here. It will be interesting to see how that compares to your slurry test.

But, don't do it until your plants are ready to be watered/fed again. You want to let the soil dry for the sake of your plants.

Ok, so I did a drench with a bloom fertilizer solution. It had been 8 days and they looked like they needed it.

Solution water = pH 6.7 and 1150 ppm
Leach water = pH 6.4 and 1900 ppm

This tells me my slurry method was pretty accurate on pH but not even close to TDS! Any thoughts?

I know I'm supposed to wait an hour and run another 12 oz of water through it, I may or may not do this, not sure I will learn anything more from it.

for anyone who cares, there are some minerals that can be leached and some that are impossible to leach. testing run off tells you nothing about what is in your soil, only what the water picked up as it ran by real fast. chasing ph will also make you crazy, especially in soil.

You have excess build up of nutrients,id run more nutrient solution through until that runoff ppm isnt so high...and then feed them less from here on out,monitor your runoff,while its not totally accurate it can give you a heads up with build up.

AtticGrower002 said:

I know I'm supposed to wait an hour and run another 12 oz of water through it, I may or may not do this, not sure I will learn anything more from it.

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That was an important part of it. Measuring runoff coming out immediately isn't very meaningful. It didn't have time for the soil to impart it's pH upon the liquid. The theory of that method is that the liquid sit in the soil and equalize for an hour. Then, displace only a measurable amount (i.e., don't dilute the equalized liquid any more than you have to to get a measurable amount.).

Regarding your runoff PPMs. If you took the soil sample from the top, it may not have much salt. It may have collected further down.

For me, 2000ppm is where I feed with more runoff and/or reduced strength. I like to keep it around 1800ppm (0.5 scale) in flower. If it goes to 2200, I feed 1/4 strength or water only (50% runoff, or more). If it reaches 2500 I'll see the plant falling apart.

I got a great idea, seeing as good ole az2000 got you chasing your tail right off the bat, how about posting a picture so we can see what the problem is, instead of just playing some stupid game that does nothing but hurt your girl.

oh, And I bet i already know what your problem is, red stems and yellowing leaves.




















distilled water

chuck estevez said:

I got a great idea, seeing as good ole az2000 got you chasing your tail right off the bat, how about posting a picture so we can see what the problem is, instead of just playing some stupid game that does nothing but hurt your girl.

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I posted a link above (https://www.rollitup.org/t/please-help-whats-wrong-with-this-leaf.893678/). This was a prior thread when my problems started, pictures are there, Az has seen them.
Playing some stupid game? umm.. I haven't done anything to my girls without much premeditated thought, just trying to use Az's advice to better understand my situation. First time grow here and lots to learn.