What planting mix are you using that has a pH that low?
Chili peppers grow best in soils with a pH on the 6.0 to 7.0 range.
Adding lime to your potting mix may not help since it can take several months for that lime to react and change the pH unless you used something like Quick Lime, a very hazardous material.
I'd change what I was using for a potting mix.

May be this case is a bit complicated, no one is response
:-).

I have 4 containers with LOW pH level. I have been Googling since I have found it but there is no tips to increase the pH level faster except mix garden lime in the soil in advance. To fix the problem (pH buffer) I did re-pot again today. I added nutrients rich potting soil to the old soil and keep the pH level 4-5. Such as 3 parts old soil and 2 parts nutrient rich potting soil 0.5 part cat litter, pH level is 5.

The medium I used was first experimental medium, I put garden lime and time released fertilizer when I prepared it. Now I knew garden lime takes time to increase the pH level. So for this experimental soil should be prepared in advance may be 3/4 months before it use. All these plants were healthy when I re-potted but now they are the worst in my garden. I got my new digital soil tester yesterday and I did a soil test for all my containers, the containers with 4-5 pH level are the best plants I have.

So the problem has been solved and this thread is closed.

Caelian

Kimmsr, you posted while I was posting my post. Thank you for your response. The medium was pine bark based. These 4 containers were for experiment the rest of my containers I have used my own soil recipe they are pH level in 4-5.

I agreed with your opinion, thanks.
Caelian

Are you confident that your measurements are accurate? It's hard to imagine plants would grow at all at pH 3.5. :-o

I think so. I have tested some different medium all the results are different. The tester is brand new. it can show from 3.5 to 9.0 pH level. The four containers had lower than pH 3.5 so the tester show LOW. They stopped growing they have not died but they were dying. I am not an expert on soil, I do not know what it could be happened if I washed all the soil from roots and re-potted to this LOW pH medium.

Thank you for the question.

Caelian

Something is wrong - pine bark based potting soil should never test that low. I'd suspect the pH meter's accuracy before I'd accept that as a true reading. As noted, very few plants can survive in that low a pH.

What was the cat litter made from? That could be a potential source of low pH but I'd still say it was a reach to hit 3.5.

I would be suspicious of those pH measurements. Pine bark fines are typically cited as having a water extraction pH of 4-5. Straight sphagnum peat moss can be as low as 3.5, but more typically is ~ 4.5. Seeing a soil pH of 3.5 or lower would lead me to suspect either contamination or a faulty measurement.

How are you measuring the pH? Have you been feeding the containers with anything, perhaps fish emulsion?

I give the same treatment to all my plants. I did test the soil with the plants and without the plants the result are the same. After I mixed potting soil pH 5.0 the pH level changed to 4-5. Fish emulsion is not available here. I followed the instruction of the tester for pH measurements.

Caelian.

I suspect your pH measurements are a bit off. Since you're working with containers and container media, you will probably be better served raising the questions in the Container Gardening Forum, link below.

Here is a link that might be useful: Container Gardening

Gardengal48, usually I do re-pot three times at least. In the second pot the plants have grown very well. The soil were not pine bark based but peat based soil. When I re-potted to the final pot with the pine bark based medium (low pH), the plants had peat based soil on the roots, that was the reason the plants were not died very fast. "As noted, very few plants can survive in that low a pH" I agreed with you. Because of this low pH my plants are dying.

The cat litter I have used is DE cat litter. Many bonsai people use it.

Txeb I have read about pine bark based medium in the Container Gardening forum. I have read pros and cons of this medium. That's why the rest of my containers over 40 have not used this medium.

In any case something goes wrong with my experimental pine bark based medium. The plants haven't grown well so it shows better than the pH soil tester :-). It is not contaminated because I have used it by adding peat based potting soil. Adding peat base potting soil is the best way to increase the pH level now I found the solution of my problem.

Thank you very much for all of your opinions.

Caelian

pH meters are notoriously inaccurate. If you are using a commercial potting medium, you'll find that they have been adjusted for pH before packaging. Mine is a bark based mix (Fafard) and has lime added.

Those inexpensive "pH meters" garden centers sell sell are notoriously innaccurate. I have taught classes and had some of those students bring the meters they had in and we cleaned the probes with distilled water (pH of 7.0) and had a difficult time getting those meters to zero in on that 7.0 and then tested them in Vinegar (Acetic Acid) and many read that as 7.0 and then some Chlorine Bleach and those meters still would read 7.0. Sometimes one would read the Vinegar as 3.5 pH and then follow that (after cleaning with distilled water) with the Chlorine and a reading there of 3.5 pH.

kimm - just so you know, good distilled water has a pH around 5.6 +/- ~0.2, not 7. Good RO water is typically ~ 5.0-5.5.

This post was edited by TXEB on Sat, Jun 22, 13 at 7:39

Symptom: Plants live, but don't grow.

If one of the first answers/questions you have is NOT to ascertain pH, please do not play. Because if you do not regularly test for pH, but have reasonable observation skills, this is usually the first clue your pH is out of whack at the low end of the scale.

If you don't catch this, eventually, they may not make it. But in the short term it's survivable with no lasting effects.

Stuff happens. This is life. Yeah, it shouldn't, and ninety some odd times out of a hundred, it doesn't. But every once in a while, it does. To say that it shouldn't makes the seagulls on Finding Nemo look like intelligent conversationalists.

The symptoms fit the diagnosis. The remedy is consistent with both. The question that was asked still has not been answered, but really never needed to be, given information that later emerged about how things are grown in this situation.

If the problem is low pH, what do you do? Obviously, the answer is to question the analysis.

TXEB's Soil contamination theory is more reasonable than the blame to the pH measurements.

Rhizo, commercial potting medium are pH adjusted, I agreed.

Many of the Inexpensive Soil pH testers may not be very accurate. I have three two of them always show around 7, but when I use vinegar diluted water the pH level has changed. Last year I used vinegar to lower pH level just experiment.

Strobiculate, my question was about liming the container soil to increase the pH level, what a silly question. After I posted and I found that liming cannot increase the pH level quickly. Only the solution I used was added potting soil that adjusted the soil pH. This is the answer and another question of the favorable pH level of chili plants also answered by Kimmsr.

Should I return back this tester? Should I avoid to use any cheap soil pH tester in the future? What I have lost to use this device? What is my benefit from this device? Why this device response differently according to the different soil? Should I sue the company for unusable/unreasonable device marketing? The questions are already answered :-)

I have nothing to lose to use this device. I have learned that liming should be done in advance. Liming cannot make quick pH level higher. Always do not depend on the equipment I use, take the result and observe the condition of the plant to make a right decision and gardening is always a room for learning.

We got rain yesterday and this morning I gave Epsom Salt to my plants. Some pictures of pH testing.

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I think no one is playing around here, just we have been trying to help each other by sharing our knowledge, experiences and stupidity :-)

Caelian

The "LOW" sunlight.

Caelian

Any pH meter that has a dry/wet display is not a real pH meter. Real lab meters have to be calibrated with solutions each time they are used and are not cheap. That is not something I would trust. This also applies to the soil test kits found at the garden center.

This post was edited by fairfield8619 on Sat, Jun 22, 13 at 10:46

Measurement of soil pH is classically done via a clean water extraction of the soil sample - typically approximately equal weight amounts of soil and distilled water are mixed, the soil allowed to settle or the sample filtered, and then the water measured for pH. A very convenient way to do that in a lab setting is to use an ion selective electrode made for pH measurements.

The problems with the usual probe insert measurements of soil pH are several fold. First, the measurements are not calibrated, nor are they adjusted for temperature (pH measurements are temperature dependent). Second, the typical metal electrodes are prone to surface oxidation, which interferes with any measurement of electrical potential (pH meters are really just volt meters). In some cases that surface oxidation can become severe enough to be an insulator on the electrode surface, which basically defeats the measurement of pH. Third is the electrodes are not selective - it's a crude potential measurements, but depending upon the electrode construction may respond to anything that changes electrical potential (such as soil moisture level). Finally, without a correlation study of the specific probe measurement to traditional soil pH measurement, it's not at all clear what the number shown really means relative to classic soil pH determinations.

It's not that the probe and meters are junk or meaningless, it's just that it is never clear what the number shown really means. Seeing 5 or 6 or 7 on a display cannot be taken as reflective of the soils actual pH unless the correlation study has been done. A probe reading of 5 may actually be an indication of a soil pH of 7, or 6 or 8, or anything reasonable.

This post was edited by TXEB on Sat, Jun 22, 13 at 11:08

Thank you all again for sharing your opinions.

Caelian