Doc Bud explaining why you shouldn't worry about PH in living soil

Doc Bud;2469984 said:
B A R;2469935 said:
Thanxx Sue. My post wasn't a plug for PJ's Soil mix but more for what I think about when folks say they don't need to adjust they're PH levels. I may be wrong but if this chart is correct it's the only explanation in my opinion & if so that could mislead a lot of growers with very high or low PH levels into thinking "that since so & so doesn't have to adjust using such & such I don't have to either". No dis-respect to Organics.


pH_chart724.jpg

I believe I can add something here that will clear up the confusion.

As someone who hasn't checked pH, let alone adjusted it, for the last 3-4 years now, and as someone who understands a bit about soils, here are the facts. This isn't my opinion....these are facts and I can back them up.

1. charts that show nutrient availability at different soil pH like the one above are based on NPK, sterile soil, corporate salt farming science. (yes it is science.) In sterile soil, barring other factors (see number 2 below) these charts are accurate and correct.

2. The "other factors" that are often forgotten is that soil itself is a powerful buffer. In a properly designed soil, like almost every commercial potting soil out there, the soil is pH balanced, usually with Dolomite and/or limestone. What this means is that even if you water with pH 3....the buffering ability of the soil will bring the pH back into range. It takes many gallons of water....hundreds of gallons....to alter the pH of a decent soil. So, most soil growers do not need to pH at all, even if they're using hydro nutes in the soil.

3. When talking about a biologically active soil, where root systems are colonized and healthy, pH becomes even more meaningless because the "critters" in the soil excrete humic and fulvic acids all the time in order to release minerals from the soil and feed the plant. They make subtle pH changes as needed, depending on what they're trying to "eat." The biota adjust pH automatically, in real-time, and they don't use phosphoric acid or sodium hydroxide to do it! They use humic and fulvic acid......24/7.

So, to summarize, there is no good reason to pH water in a decent soil grow.

However, there are two good reasons to NOT adjust pH in a decent soil grow:

excess phosphorus from pH down....excess sodium and/or potassium from pH up.....both of these will hurt CEC and produce less healthy plants.

Hydro is completely different! There is no biota and no buffers, so getting the pH right is critical.

Doc Bud;2470004 said:
It's part of the panoply of cannabis mythology! You're not the only one who is confused by this stuff.

If you're growing in perlite or hydroton clay....pH is critical as both of those mediums have no real buffering ability.

Coco.....I don't go there.

Peatmoss: often has a pH of 3-4....needs to be buffered with limestone. No amount of pH-up in the feedwater will compensate for the acidity of the peat....limestone must be added. After this is done, no amount of pH up or down will change the pH of the soil.

However, there is something about water that we should all understand:

Total Alkalinity. (TA)

This is a measurement that shows how much sulfuric acid must be added to water to lower the pH to 4.5. This measurement is expressed as mg/l CaC03. Most of the buffering capacity in water is due to CaC03....not all, but most. Calcium Carbonate is used because it indicates how much CaCo3 must be added to pure water to produce the TA being measured, even though perhaps 5-6% of the TA is not due to CaC03.

TA should be kept below 200. Optimal levels are around 50-100.

While pH is meaningless, TA is not. If your water has very high TA, bicarbonates will form in the soil and everything will get screwed up and nothing will work right.

For the record, everyone who has listened to my advice to stop pHing has been pleased with the results. If you're in soil, I strongly encourage you to cease the practice.

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