Ph and alkalinity what’s the difference

I’m fairly new to growing and have had problems with ph as many of us do starting out on this adventure. I’ve had numerous question pertaining to PH ( power of hydrogen) and chemicals that can safely be used to raise or lower it. I’ve recieved good info from all however , while researching water , alkalinity, and ph I’ve read numerous articles explaining the correlation between ph and alkalinity and each article is insistent upon the fact that although ph can identify whether water is alkaline or acidic, the two ( ph and alkalinity ) are different and although I may adjust my ph to a proper level with a chemical agent , these chemical agents do not rid the water of the metals and particles etc that cause water to become alkaline , they just “buffer” them. These can then build up in the soil and even though I’m adjusting my PH the presence of these alkaline causing materials will affect the growth of my plant even inhibiting roots uptake of water and nutes. It’s my understanding that they are not the same even though science gives us the double meaning. I don’t want to pretend to know everything about ph etc. i first sought to just learn more but now I don’t give a @#$&& I’ll use distilled water buffered to 6.5 my little grow doesn’t require ppm etc anyway a couple pics from what I’ve read. Please correct me if my understanding is wrong

I understand your concern with this. My water comes from a very alkaline well. I have to filter my water to wash my hair! I’ve grown in very soft water too. Either way, I just ph to 6.5 and call it a day. Working out great. Take a look at what I’m about to harvest now in very very hard water. It’s in my grow journal. I dont save my pics on my phone lol. And akaline just means a ph of 7 or more. I’m guessing your referencing hard or soft water?


Like @VoodooKing I am in wellwater, pH about 8 and ppm’s around 180, leaves lots of white calcium residue everywhere. I just roll with it as is and pH down to 5.8 for my coco. As the alkali salts and other salts build up overtime in the coco, if it’s impacting my plants, I flush them.

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I was using my well water it’s 5.3-5.7. I do/did adjust to 6.5 however without adding any nutes and using a “base”potting mix , I experienced lockout of both nutes and water and that was due to my alkalinity either too high or to low I don’t know which and I don’t give a crap anymore lol. It may sound funky but that’s my understanding of ph and alkalinity. Although the terms have double meaning etc they ARE NOT the same are not measured the same and alkalinity can be buffered but not changed in water. So anyway I’m not doing anything so big I need to concern myself with run off and ppm etc. I thought I may to get better results but with the little personal that I grow , it’s just too much trouble for me and due to what I’ve learned here and there I’m satisfied with how I handle my ph issues. I was actually attempting to open discourse on alkalinity and ph. There are those that believe they are the same , some think that adjusting ph automatically adjusts alkalinity and although it will buffer the alkalinity it really doesn’t change the alkalinity or the water only buffers for a short time for that you need to adjust alkalinity which can be high or low even though the ph is adjusted to our desired level the alkalinity is only buffered not changed and these buffers wear off in time and allows mineral salts to build up therefore we can adjust our water ph but if we don’t watch our alkalinity ( ppm ? ) the plants can’t benefit from anything we do unless we flush the media of the minerals etc causing the problem. Smh at it all but one thing I’m sure of alkalinity and ph are not the same even though there are those here that believe they are

Did you know that feed water with high alkalinity will substantially raise the medium Ph in the rhizopshere no matter what the Ph of the input water is???

I would think this info to be more useful to those of us that rely on groundwater aquifers or well water supplies that dont get tested or get treated to adjust total alkalinity.

Water Quality: pH and Alkalinity

Recently, some growers have expressed concern about the “high pH” of their irrigation water and its potential adverse effects on plants. The purpose of this article is to allay some of these concerns by pointing out the difference between “high pH” and “high alkalinity”.

Alkalinity and pH are two important factors in determining the suitability of water for irrigating plants. pH is a measure of the concentration of hydrogen ions (H+) in water or other liquids. In general, water for irrigation should have a pH b etween 5.0 and 7.0. Water with pH below 7.0 is termed “acidic” and water with pH above 7.0 is termed “basic”; pH 7.0 is “neutral”. Sometimes the term “alkaline” is used instead of “basic” and often “alkaline” is confused with “alkalinity”. Alkalinity is a measure of the water’s ability to neutralize acidity. An alkalinity test measures the level of bicarbonates, carbonates, and hydroxides in water and test results are generally expressed as “ppm of calcium carbonate (CaCO3)”. The desirable range f or irrigation water is 0 to 100 ppm calcium carbonate. Levels between 30 and 60 ppm are considered optimum for most plants.

Irrigation water tests should always include both pH and alkalinity tests. A pH test by itself is not an indication of alkalinity. Water with high alkalinity (i.e., high levels of bicarbonates or carbonates) always has a pH value ÷7 or above, but water with high pH doesn’t always have high alkalinity. This is important because high alkalinity exerts the most significant effects on growing medium fertility and plant nutrition.

High pH and High Alkalinity Effects on Plant Nutrition
Potential adverse effects. In most cases irrigating with water having a “high pH” ( 7) causes no problems as long as the alkalinity is low. This water will probably have little effect on growing medium pH because it has little ability to neutralize acidity. This situation is typical for many growers using municipal water in Massachusetts, including water originating from the Quabbin Reservoir.

Of greater concern is the case where water having both high pH and high alkalinity is used for irrigation. In Massachusetts this situation is most common in Berkshire county. One result is that the pH of the growing medium may increase significantly with time. This increase may be so large that normal lime rates must be reduced by as much as 50%. In effect the water acts as a dilute solution of limestone! The problem is most serious when plants are grown in small containers because small volum es of soil are poorly buffered to pH change.Therefore, the combination of high pH and high alkalinity is of particular concern in plug seedling trays. Trace element deficiencies and imbalances of calcium (Ca) and magnesium (Mg) can result from irrigating with high alkalinity water.

It is much more difficult to predict the effects of irrigating outdoor flower crops, gardens, and landscape plants with water having high pH and high alkalinity. On the one hand, in some parts of the United States, long-term irrigation of crops with water high in bicarbonates and carbonates has led to yield-limiting trace element deficiencies which must be corrected with special fertilizers. On the other hand, in New England, several factors probably act together to partially offset the effects of high alkalinity water. First, rainfall levels are relatively high and historically this has caused Ca and Mg ions to leach from the soil. These are replaced with H+ and the result is acidic soil. Second, this acidification may be helped along by the rather acidic rainfall common in this region in more recent times. Third, acid-forming fertilizers also help counteract high pH and alkalinity.

Potential beneficial effects. For some greenhouse operators, water with moderate levels of alkalinity (30-60 ppm) can be an important source of Ca and Mg. With the exception of Peter’s EXCEL and a few other fertilizers, most water soluble fertil izers do not supply Ca and Mg. Also, the Ca and Mg from limestone may be inadequate for some plants. Moderately alkaline water could be beneficial as a source of extra Ca and Mg for crops prone to Ca and Mg deficiencies (e.g., poinsettia).

Other Effects of High pH and High Alkalinity
In addition to nutritional disorders of plants, water with high alkalinity can cause other problems. Bicarbonates and carbonates can clog the nozzles of pesticide sprayers and drip tube irrigation systems with obvious effects. The activity of some pesticides, floral preservatives, and growth regulators is markedly reduced by high alkalinity. When some pesticides are mixed with water they must acidify the solution to be completely effective. Additional acidifier may be needed to neutralize all of the alkalinity. To determine if a chemical is affected by high alkalinity, carefully review the product’s label. Unfortunately this potentially important information is not always printed on the label, so considerable extra effort may be necessary to find the inf ormation. A call to the manufacturer will probably be needed for most chemicals.

Acidification of High Alkalinity Water
Many greenhouse operators inject acid (e.g., phosphoric, nitric, or sulfuric acid) into water with problematic high levels of alkalinity. Acidification of water having high pH but low alkalinity is rarely necessary. The use of acid injection sh ould be considered very carefully for several reasons. First, it is an extra step in production which will require additional materials and equipment. Second, acids are dangerous to handle and may damage some injectors and piping systems. Third, phosphoric or nitric acid are sources of P and NO3, so the regular fertilizer program may need to be modified to take into account the addition of these nutrients. This would depend on how much acid must be used to neutralize the alkalinity and reduce pH. Fourth, sometimes acid injection causes the solubilization of normally precipitated (unavailable) forms of trace elements resulting in levels toxic to plants.

The amount of acid required to reach the desired pH (i.e., neutralize alkalinity) is determined by laboratory titration of a water sample with the appropriate acid or by a calculation procedure. Some “fine-tuning” may be needed later when actual inject ion is started. Acid is always injected prior to the addition of fertilizer or other chemicals.

Prepared by Douglas Cox
Plant and Soil Sciences
University of Massachusetts

Right on ! You go bro ! That’s what I’ve been trying to say ; that ph and alkalinity are not even close to being the same but was told by some here and elsewhere that it was. It’s what I’ve been unable to articulate and it should quiet down the naysayers that ph/alkalinity are not the same not measured the same etc this is vindication Your article explains it much mo’ betta’ thankyou for that info a great and welcomed article. I’ve been thinking about using rain water but with all the aluminum oxides and nano particles they’ve been dousing the skies with I’m not sure that’s a good idea when a lot of non gmo fruit trees seem to be affected by it around the globe. That’s another story for another page

Thankyou voodooking for that easy to read and understand article you provided. Says everything I couldn’t articulate nor fully understand

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Did you ever check your runoff? Just b/c you put in 6.5 h2o doesn’t mean your soil biome won’t change the pH.

If you keep your pH runoff controlled, you won’t have pH issues. There are chemical & biological processes that occur in your grow medium, so adding a rote 6.5 measured input doesn’t necessarily mean your output will stay at 6.5.

If you play lose & fast with your pH, you will encounter problems. Growing using organic soils/methods is pretty much the only method not dependant on keeping critical tabs on your pH.

So, check/adjust the pH of everything going IN, and check the pH of everything coming out. Then, use the last output number to adjust your next input number.

Flush regularly to get rid of build up, such as that from high alkalinity water & nutes, to keep pH & tds within healthy levels.

If you need to do hardcore pH adjusting, you might benefit from using ro or distilled water with whatever pH adjusting chemicals you’re using.

You should check out some of Cornell’s pdf files on pH. Just google it.:grinning:

PS. not arguing the difference of the 2, but simply stating that for our growing purposes, pH definitely matters, as does water alkalinity.

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Absolutely! type in LIGHT BULB SOCKET SPLITTER in the search box. The ones I recieved today are made by Jackyled ? I purchased mine for $4.61. Today they are $6.31 ea and many configurations to choose from. I also bought some E26/27 to E39/40 the large mogul base for photography studio type CFLS which are way beyond what I’m currently using and large Corn Cob LEDs withmogul bases

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Smh lol don’t know what happened there :stuck_out_tongue_winking_eye: I did just get back from all day at universal but I think it’s due more to the inhalation of majane than being worn out, that post is totally in wrong place and I sent to wrong person. So sorry :pensive: hope you can use it though

It’s a nifty fixture, for sure.

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Yepyep I got tired of getting frustrated with these ghetto rigged double socket splitters I was using so just started an online search that took 3 minutes and I’ve been ragle#%#%#$ with these for 2 yrs lmao kept getting better with them though ha. E26 to E39 adapters too

I bookmarked it, in case I ever go that way, so your mis-post was not a waste. :grinning:

Yep I’m turning away from them as an all around use veg/flwr it as I purchase LED full spec but I think I’ll still use the 5k-7200k for veg. I really hope it helps all those who’ve been frustrated with their cheap light rigs too lol