Do you adjust pH when watering?

[orchids3]

I too found something that worked and stuck with it. Greencare fertilizer is good stuff and I was successful with it. The problem with the Greencare is that it absorbs watter and turns too mush too fast here in humid Florida so I switched to Jacks Professional for RO.
With my water I get a good pH without ajustment with Jacks but had to ajusst pH down with Greencare.
I saw Calcium carbonate mentioned in water - I have it here as well - around 300 PPM. I understand that this form of Calcium is not available to the plant and should not be considered. I ajust my calcium as if there were not in the water. Is this correct? The buffer I use is Gypsum in my cymbidiums - it adds calcium and buffers against pH shifts. Does anyone else use it applied as a
top dressing? I recently saw a thread in another forum that repeated an old chart first published by the California department of Agriculture then publised in Bob Gordons book which indicated that most nutrients are most available to the plant at a pH of 7. Would love to publish the link but links seem not to post. The only reason I say that is that obviously there is some differance of opinion about correct pH. I continue to use
5.8 to 6.2 as my target as indicated by Bill Argo. My epiphytes do grow much better since I started ajusting pH in fact they are taking over the greenhouse and everything needs repotted instead of dying like they used to. The cymbidums are doing better as well.

[IdahoOrchid]

Here is the link referred to:

Picasa Web Albums - George - nutrient avai...

[orchids3]

I forgot to add that the main reason for using gypsum is that it nutralizes salt. A lot of our water in Florida has salt in it. Mine included. Our use of ground water here reduces the water table somewhat and allows sea water intrusion. Florida is basically one big sand bar so it will become more important and noticed as the population increases. When I first moved here my well was artesian - now I have to pump the water more than 50 ft. . the loss of outward water pressure is what is causing the seawater to flow into the aquifer - just another concern to those of us who grow salt sensative plants. I cant quote a scientific paper on this subject - its just my take on whats happoning -----

[goodgollymissmolly]

Originally Posted by orchids3

I forgot to add that the main reason for using gypsum is that it nutralizes salt. A lot of our water in Florida has salt in it. Mine included. -----

I don't think I agree with that. The salt in your water is presumably sodium chloride resulting from the ground water dissolving sodium chloride from the ground. Whether the origin is invasion of sea water is arguable, but not really part of my problem here.

Gypsum is calcium sulphate. Most calcium salts are basically insoluble in water and gypsum is indeed insoluble for practical purposes. Nearly all sodium and all chloride salts are very soluble in water. Those are generalizations so if you have to guess at an answer on the SAT this would be your best bet.

I do not know what you mean by the quote above. Adding gypsum to water containing sodium chloride does nothing whatsoever to the sodium chloride. It adds insoluble gypsum particles to the mix. Additionally, unless you are dealing with pure calcium sulphate, not the mined mineral known as gypsum, you are adding some soluble species that are not especially desirable. The first of which is more sodium chloride and several sulfides that might be partially soluble.

There is no science supporting your statement that "gypsum neutralizes salt". Please do not think that I'm disagreeing with you personally, it's just that your statement is not factual. This is the kind of thing that gets spread by the internet and never goes away. As one wise person said, "It takes twice as much data to overcome a first false impression than to reach the correct conclusion in the first place". I'm just trying to nip this one in the bud.

Sincerely,
Jim

[orchids3]

Jim,
You may be right but horticultural gypsum is sold in Florida as an amandment for the express purpose of nutrilizing salt - NaCl - . I would like to find something better but have used it as a top dressing on cymbidiums for several years. At least there have been no adverse effects that I can see. Can you recomend something better? The comment about salt intrusion was based on observation of my own well over a 20 year period. The local authorities once restricted watering lawns for the reason that the drop in water table would cause salt intrusion.
The same authorities then drilled a 300 ft well and proceeded to pump it to the whole city. Some of our shallow wells went dry - others show an increase in salt. I am less than 5 blocks from the St Johns river (Brackish and 15mile from the Atlantic.

[goodgollymissmolly]

Gypsum is sold as a horticultural material generally as a soil amendment to break up clay like I have here. Because it is insoluble it can mechanically "loosen" up the soil and help to prevent anaerobic conditions. I think the addition of organic materials like leaves and decayed munch work better, but gypsum can help if immediate relief is needed. The main purpose that gypsum is sold is that it is cheap and needs a market besides drywall.

Anybody who tells you that gypsum "neutralizes" salt is either greatly misinformed or downright dishonest. It just ain't so.

Again, I want to emphasize that I'm not criticizing you, just the junk science. You are not the problem, but just a victim of misinformation.

I'm not saying gypsum will harm your plants. It won't do any good either.

[IdahoOrchid]

Sulfur (in some form or another that I don't recall at this moment) is used for the same purpose in our area: to loosen and break up soil compaction. I have heard of gypsum being used for that also.

[orchids3]

Yes probably sold by the same people - and there are a lot of them - who sell high phosphate fertilizer as a "Bloom booster". This thread tells me that I need to research gypsum further - my old friend who taught chemistry at MIT probably will know. I admit to not being a chemist at all. Am really concerned about the salt I am seeing 17 ppm two years ago 22 ppm recently. Have lost a botanical I really liked and believe salt to be the culprit.

[newflasker]

Originally Posted by goodgollymissmolly

Gypsum is sold as a horticultural material generally as a soil amendment to break up clay like I have here. Because it is insoluble it can mechanically "loosen" up the soil and help to prevent anaerobic conditions. I think the addition of organic materials like leaves and decayed munch work better, but gypsum can help if immediate relief is needed. The main purpose that gypsum is sold is that it is cheap and needs a market besides drywall.

Anybody who tells you that gypsum "neutralizes" salt is either greatly misinformed or downright dishonest. It just ain't so.

Again, I want to emphasize that I'm not criticizing you, just the junk science. You are not the problem, but just a victim of misinformation.

I'm not saying gypsum will harm your plants. It won't do any good either.

There is a mix up between horticulture and chemistry. Some people provide information about horticulture using knowledge of the chemistry. Sometimes it's good but sometimes it's bad. The term "insoluble" in chemistry is just a relative term. It's is used to compare the solubility of a chemical to another. Example, calcium sulphate is insoluble comparing to calcium chloride or calcium nitrate because the solubility of calcium sulphate (few grams per liter) compare to calcium chloride (hundred grams per liter). When this term applies to horticulture it may not appropriate. In horticulture, insoluble or few grams fertilizer per liter could be good; hundred grams fertilizer per liter means killing plants.

The term "neutralize" in horticulture could be different than in chemistry. It could mean ion exchange in soil. Ion calcium and magnesium are used to "eliminate" ion sodium and potassium in medium. People are using calcium nitrate and magnesium sulphate to eliminate Na & K in Coconut chips.

Using only "insoluble" "neutralize" term to draw a conclusion that gypsum is "....." is misinformation. There are hundreds of researches about using gypsum as well as functionalities of gypsum in horticulture.

[goodgollymissmolly]

Chemistry is chemistry, there is only one set of facts. There is no separate of science for horticulture. As a wise guy once said, "You are entitled to your own opinion, but not your own facts".