Hman,

I use Citric acid. As far as I know, it's the most common buffer. I've read several recommendations for it by university publications. My chem supplier carries it in 50 lb bags, but I purchased mine off the internet. It's dirt cheap.

My water is very alkaline and runs b/t 9.3-9.5 pH. This is both according to our water district report, and my personal testing.

It doesn't take much citric to buffer the water. On my water, one teaspoon per 16 gal of water will bring it down to 6.5 ph. One teaspoon per 25 gal of water will bring it down to a 7.0

I generally shoot for 6.5 because almost any pesticide is stable for a long period of time at that pH. Sometimes I buffer to 7.0 because one compound I use doesn't like acidic water(I believe it's Delegate, but I don't have the label in front of me.) You probably remember not to use a buffer w/ copper.

Lastly, if you get the water too acidic, you may run the risk of foliage burn.

Thanks OP, just what I was looking for.

Hman,

The 2011 Midwest Fruit guide had this to say about the mix rate:

"Granulated food grade citric acid may be the most convenient and inexpensive acidifying material. Two ounces per 100
gallons has been shown to reduce the pH of tap water
from 8.3 to 5.4. Convenient granulated food grade citric acid measures are:

per 100 gal 1/4 cup, slightly rounded
per 300 gal 3/4 cup, rounded
per 500 gal 1 1/3 cups

Granulated food grade citric acid is available in 50-
pound bags from suppliers that handle food grade
chemicals."

You may notice the guide recommends much more citric than I use. Part of the difference may be that I only take the pH down to 6.5, whereas they go to 5.4.

But the other part of the difference may be the amount of alkalinity in the water. Alkalinity is ability of the water to absorb acid without changing pH (the equivalent of CEC in soil.) Some waters can have high alkalinity and it takes more citric acid just to move the pH a little bit.

I've got plenty of citric. If you'll email your address, I'll send you some.

I use a tblsp of miracle grow acidic fertilizer with a 4 gls backpack sprayer for many years and i do not see any problems.I thought a foilear spray of fertilizer with chemicals is a good idea to me.

Olpea, thanks for the offer, but I already ordered some.

Yeah, when you suggested acidic spray might scorch leaves the first thing that came to my mind was all the urea sprayed on apples at this time of the year. Wouldn't that make for a very acidic spray?

It's KH (carbonate hardness), also known as alkalinity that buffers water. The "K" in KH comes from the German word for carbonate. Adding acid to water to lower pH is a brute force attack on the buffering capacity of the water. Using this method to lower pH is not completely reliable or stable. You need to know the KH of your water, the pH of the acid, and apply a bit of science as well as trial and error.

Another way to lower pH, if you're not dealing with a large amount of water, is to use water with the KH and much of the GH removed. Such water choices would include distilled, R.O. (reverse osmosis), or rain water. If you are working with smaller amounts of water, this might be the better way to go. Here locally we can get a 5g refill of R.O. water for around a buck -- perfect for drinking or watering a small blueberry patch. R.O. water has the added advantage of having the chlorine/chloramine and any other solids removed as well.

I have a R.O. water filter that puts out 100 gallons a day which i store in barrels for spraying

I've long used distilled water when I mix Imidan in a jug to use enough to spray 25 gallons at a time. Only recently did I learn that the DW was too alkaline and I did experiment with my buffer to get it in the 5's.

Mostly my concern is about Imidan so 6.5 would be too high. I used to put unbuffered water in my spray tank and never noticed failure as a result of alkalinity, but now I test and buffer.

Probably be phasing out the Imidan in the next couple of years anyway.

Thanks for the chemistry lesson, Mr. Clint. What I draw from it is not to blindly follow a recipe as if all water of a given pH is equal.

This is more about the properties of water than general chemistry. I don't think that the KH, GH, and pH interaction applies to all liquids.

Someone may have charged you for distilled water but gave you a mix of tap water instead. DW will have zero alkalinity, as it is basically condensation that's been captured from boiling water. All the alkalinity (KH) is left behind when the water turns to vapor. The pH of DW should be in the 5.5-5.8 range.

Having worked with aquariums and swimming pools for a number of years, it's helpful to understand the properties of water. If you are going to do much water tinkering, you will want to pick up a cheap pool or aquarium test kit.

Thanks,Mr. Clint. Interesting, I had thought DW wouldn't have anything in it to break down Imidan but when I tested it with paper it looked to be in the 6's. Maybe I just read it wrong. Don't have anything better to test water.

The paper test strips can be inaccurate sometimes. If your DW was in the upper 5's, the test paper might have been off by a few points and looked to be in the 6's. Not sure how precise you need to be for this particular application, but I would say that you are probably OK to use the DW that you have.

I had always assumed that distilled water had a PH of 7 (shows what a Chemical Engineering degree gets you :) ). When I saw this thread I started Googling it and found the following. It looks like there are a range of PH for distilled water from around 5 to just below 7, depending on how much CO2 has dissolved from the air and the presence of any volatile contaminants. So Harvestman's PH reading could be spot on.

"Distilled water ideally consists of only hydrogen and oxygen, with a completely neutral pH of 7. In reality, it almost always is slightly acidic, from 5.6 to just under 7, because the water absorbs carbon dioxide from the air."

and

"Distilled water is water that has been boiled in an apparatus called a "still" and then recondensed in a cooling unit ("condenser") to return the water to the liquid state. Distilling is used to purify water. Dissolved contaminants like salts are left behind in the boiling pot as the water vapour rises away. It might not work if the contaminants are volatile so that they also boil and recondense, such as having some dissolved alcohol. Very elegant stills can selectively condense (liquefy) water from other volatile substances, but most distillation processes allow carry-over of at least some volatile substances, and a very little of the non-volatile material that was carried into the water vapour stream as bubbles burst at the surface of the boiling water. Maximum purity from such stills is usually 1.0 MWcm; and since there is no protection from carbon dioxide (CO2) dissolving into the distillate the pH is generally 4.5-5.0. Additionally, you have to be careful not to re-contaminate the water after distilling it."

and

"With respect to the preparation procedure and expelling of gases during boiling, it is understandable that distilled water pH scale falls in the neutral range (pH 7). Nevertheless, in most cases, the pH of distilled water is slightly acidic (around pH 5.8). Some sources even report the distilled water pH level to be as low as 5.5. Generally speaking, the pH of distilled water is below 7 or neutral value."

Bob

This subject is more complex than I imagined but I find all the input extremely interesting. Thanks, Bob. I'll be checking the pH of my distilled water.

Allan: no doubt by now you've realized that water chemistry isn't as simple as you might expect, darned it!

Here is a direct answer to one of your questions but essentially useless unless you are using my water, if not you've got some analytical work to do. My water is pH 7.2 and requires 20ml/gal 5% standardized acetic acid to drop the pH to 5.5. Once dropping the pH in a gallon of water to 5.5 with acetic acid, the pH will no doubt drift up as the bicarbonates in my water dissociate into CO2 and H+, the CO2 , which is acetic, off gases under certain conditions driving the pH up.

I acidify my irrigation water to get rid of the bi-carbonates as they wreak havoc with my calcareous soils and cause Mn, Zn, Cu and Fe to get tied up in the soil, Fe is the worse. The added bonus to acidifying is the H+ follows the irrigation water into the soil where it can act to drop the pH. The CO2 simply off gases and causes global warming, What I won't do to get a few apples!

You might want to get a pH meter as test strips can be well, a little off. I broke down and bought an Extech brand waterproof meter for about $80.00 and 2 bottles of pH buffer for calibration purposes. Funny thing, My test strips gave me very inconsistent results when comparing directly with the meter, I was not surprised. In case you buy a meter, remember to buy 2 buffers to bracket the range you will be testing I.E. if your target is 6.0, a 5.0 and 7.0 buffer would do nicely. I bought a 5.0 and 7.0 for my target of 5.5. Actually, you can get by with a single point calibration ok if it is close to your target and/or you aren't concerned about being off by a few percent.

One last thing on pH meters, make sure it has automatic temperature compensation. It's darned handy that technology has made it possible to buy a very reliable, portable and capable pH meter for so little these days.

FWIW, my bias is towards good equipment, I spent many years working in and managing a plant tissue analysis lab. Man we had a lot of great equipment.

One other thought. When you have come up with a recipe, mix up a batch of water in your spray rig and use it as you would in real life and, collect some of the spray and test it to see if the pH has changed since you measured it in the tank after mixing. You might also try mixing it in the tank and letting it sit for a real life period of time and re-test. Basically, what I am getting at is treat a batch like you would in the field and then see what happens to the end product (minus the added "cides").

Surely Cornell must have something on the topic.

Michael, I'm working under the assumption that paper is reliable in that a specific pH will always turn it to the exact same color and it is the limitation of our eyes that render it imprecise- much as pH testers with color graphs and bottles of specific chemicals to mix with soils do.

Are you sure that the strips were giving you inaccurate readings and not your eyes? I don't need precision at all- just a ballpark figure within about a half point of accuracy.

I too believe in using the best equipment- as long as it pays for itself over time. I have a soil pH meter that cost me over $100 and a Cornell test kit that cost about $15 and it's the Cornell kit I generally use. The other one doesn't get me a reading in dry or sandy soil.

Allan: My understanding of pH paper strips is from 15-20 years ago so what I remember may well not be complete. Yes, the strips can be rather accurate and precise. The specific conditions that cause problems with the strips eludes me but they have to do with the water's chemistry. I.E. my water is extremely hard causing the reaction between the H+ ions and the paper to show low readings. I suspect that water with low dissolved solids would cause less interference with strips chemistry. In your circumstance, once you figure out with certainty how your strips read with your water, problem solved. If you have to fill up at numerous locations from sites with well water, I'd be leery of the strips due to the possible wide range of differences in water quality.

One thing is for certain, colorimetric methods have limitations in that they can have interferences that must be dealt with in sample preparation. A very simple example is the one I use for testing free chlorine in the 1 mg/L +- range for our town's water system. Normally, the sample turns different shades of pink which would be easy to compare to references but our water straight out of the tap causes the hue to actually change and readings iffy. I take a 1ml sample, dilute it with 1ml of R.O water, add the reagent and multiply the result by 2. The hues match very closely.

Definitely, I've found when it comes to the color red, people's eyes have different sensitivities. Maybe my eyes aren't catching the fine change from yellow to green in my strips, the reaction does take quickly from yellow going towards green. Obviously, the quality and intensity of the ambient light can make a difference too.

So, after all the above ramblings, if it were me and it was very important, I'd tell a lab what I was doing, get them to run a pH on your water and compare it to your strip reading. The lab should be able to give you all the ins and outs of strip testing that I have long since forgotten.

Good luck!

Michael, my water comes from many wells and I'm doing buffering for precautionary reasons although for years I used no buffer and never seemed to loose efficacy of Imidan. I'll probably continue to rely on paper strips and not make things too complicated. Water tends not to be as alkaline in the northeast as other regions in the country.

Managing 100 orchards efficiently requires tending to what's most important. Just as important is keeping my overhead down as the state keeps raising established and inventing new fees- not to mention my 19 year old son!

I may well take Imidan out of my quiver next year anyway, so if I happen to run into any problems this year it probably won't influence what I do next (depending on labels of what I am using).

Allan: I sent off some correspondence to someone who deals with this stuff more than I did in my lab/research days, hopefully he'll get back to me sometime.

I'd imagine managing 100 different locations totaling say, 100 acres would be considerably more challenging than 1 or 2 totaling the same total area, my hat is off to you taking the road less traveled.

One thing for sure, when a government sets a number, it will change in the way we least like. I.E. about 8 years ago the Fed. EPA dropped the permissible level of nitrate in drinking water to 10 ppm max.. Our very small town had to dig a new well, something that was a hardship. A few years ago it was Selenium, EPA dropped that from 90 (I think) to 50 ppm, ours was at 60 so we had to begin purchasing more than half of our water from a rural water district to blend ours down enough to pass. Now the EPA has dropped the level of "Gross Alpha" to the point where we have only 2 choices, drill a well 4-5 miles north of town and pipe it here, extremely expensive or go to only rural water. The problem with the rural water option is that they will only allow us 30 GPM, that stinks. A friend of mine in the mining industry described the exact same pattern to me once, many years ago.

Oh well, bureaucracy breeds bureaucracy, what a surprise!