My other question: Will gypsum raise the pH of acidic soil? Or would I still have to add some lime? Does gypsum impart any nutrients?

Gypsum has no influence on soil pH - you need lime to raise or neutralize excessively acidic soils. And the impact of lime will tend to be temporary at best. Gypsum can provide calcium, but is generally not needed in most soils. From Iowa State University: "Gypsum, or calcium sulfate, is often applied, but seldom needed, due to a classic misunderstanding arising from its association with improving water movement and soil structure on sodic (high sodium) soils that are typically found only in semi-arid climates. The calcium in gypsum displaces salt in the soil. The salt then reacts with sulfate to form sodium sulfate, which is highly water soluble and easily leaches away. Removing the salt from the soil helps to aggregate soil particles, which eventually restores the soil structure. But this situation only occurs when the soil structure deteriorates because of high salt. These wet, sodic soils are slick, sticky, and have poor drainage...very similar to heavily trafficked clay soils that are not affected by excess salt. Both situations create hard soil with poor structure and drainage. Only a soil test will determine if there is a true need for gypsum application."

I'm not particularly concerned about going organic. Whatever works, is not expensive and is pretty much safe is what I'd like to use. What about those coco wet products? Or mixing in some coir?

I thought I explained the wetting agent thing in an email last night, but to review, I said: the only time they're an advantage in soils is after you've allowed your soils to get too dry. Peat & pine bark become hydrophobic at around 30% moisture content, but they FEEL dry at 40-45%, so if you water when soils first feel dry, they won't get hydrophobic. There is one exception though - if you are using organic fertilizers, they can promote an algal scum that grows & hardens on the soil surface. This scum is very hydrophobic when dry.

If you do feel you need to use a wetting agent (I've used them for other applications where I've needed a surfactant, but never in soils) Coco-Wet is a good organic one. 'Soaps' covers a LOT of ground, and everyone thinks of detergents when the word soap is mentioned. Many are phytotoxic .....

Al

Good thing you are much more perceptive than I, Al :-)

1 part good information
1 part bad information
Mix together thoroughly
Garnish with a university seal
serve

They're doing great here:
Gypsum, or calcium sulfate, is often applied, but seldom needed, due to a classic misunderstanding arising from its association with improving water movement and soil structure on sodic (high sodium) soils

And then they turn around and feed right into the very misunderstanding they just mentioned!

the calcium in gypsum displaces salt in the soil
Removing the salt from the soil helps to aggregate soil particles

BAAAAAAHHHHHH!!!!! "salt" and "sodium" are NOT interchangeable words. They are two different words that mean two different things. Sodium contributes to salinity but salinity does not necessarily mean sodium. I have no idea how many countless hours I've spent trying to explain to people why adding gypsum to their saline soil won't do bupkis to help them leach out salts when sodium is already properly balanced by calcium and magnesium. They generally stare at me for a moment like I just moved their water dish and then pull out some quote from a university or other "expert" (much like the one above) to prove that gypsum removes salts regardless of which salts are the primary contributors to overall salinity. It makes it very hard to educate people when this sort of bullocks gets strewn about by universities and others.

Whoa, I've had too much coffee again.

That sounds really bad and not at all like what I meant. How I should have typed it is:
then pull out some quote (much like the one above)from a university or other "expert" to prove that gypsum.....

I was in no way implying that gardengal48 doesn't know what she's talking about. I know that she knows what's what.

Gardengal: What do you use to raise the pH then if lime is only temporary at best? And what test would I use to determine if gypsum is needed? A general hardness and/or a carbonate hardness test?

Al, I didn't get to read your email yet but will just after this. I'm supposed to shoot for a pH of 5 then, right? And many of my pots do dry out in the summer when it gets almost 100 degrees so I do face things getting hydrophobic. I refuse to water more than once a day. Would a drop or two of Johnson's baby shampoo be safe for the environment? I'm not into the whole organic thing so I'm not limited to only using products that claim to be organic on the package.

gargwarb: I don't think anyone thought you meant it that way. I didn't even catch it until you pointed it out.

All this brings me to wondering if coir would be a good replacement for peat. It can be salty (or do I mean high in sodium?) but I've always had good results with it. It didn't repel water or hold too much in. And I've never even mixed any perlite or anything into it but probably would if I use it for germinating. Does anyone know if it has neutral pH? What would I need to add to it in terms of macro and micro nutrients and other amendments?

When I used it in the past, I just used it straight up for potting up plants and watered with Miracle Grow but I've learned the hard way that I can't do that with my winter sown seedlings and other seedlings.

I refuse to water more than once a day

Although that practice seems counterproductive to me (why would you bother growing things in a container if you did not intend to provide them the care they require?), adding the water absorbing polymer granules could get you around that requirement.

Ms M - I think you're making it harder than it needs to be. Please don't think that you can simply shoot for and maintain a pH of 5.0, or any other pH in a container for that matter. You'll just end up dealing with frustration. If a hobby grower tells you that that he maintains a certain soil pH for his containerized plants, it's a pretty safe bet you can doubt his veracity. It's just too difficult w/o very frequent testing and correction with a variety of chemicals.

Coir has a much higher pH than peat, and that high pH virtually eliminates any chance of using lime as a Ca source w/o raising pH too high when coir is a substantial % of a container medium.

I'm, not sure why you don't just use the 5:1:1 mix referred to in the thread linked to below and use Turface or better yet - NAPA floor dry instead of perlite. You will have excellent aeration and all the water retention it's reasonable to want.

Al

I will now. But what is NAPA floor dry? Okay, I googled it. I have to go to a NAPA auto store to find it, right? I'm not sure if there's one near me... Is it cheaper than perlite? I would prefer what's cheapest.

I apologize but I still haven't read your email yet! I really need to do that!

In stark contrast with these mineral soils, the organic components of container media contain only minute quantities of micro-nutrients. These elements are very tightly bound as an actual part of the organic components chemical structure and are only released when the organic matter decomposes. Therefore, raising/lowering pH within the general limits of around 4.5-6.5 has very little effect on the availability of these nutrients. Even high media pH has little influence on the availability of micro-nutrients unless there are also high levels of Ca, Mg, Na, or bicarbonates (HCO3s).

E.g., in container soils we commonly blame the upward creep of media pH for the lack of availability of (the most common deficiencies) Fe and Mn. It may very well be true that these elements are usually less available as pH rises, but it is not the pH that is the cause. It's what is driving the pH - Ca ... and high pH is merely a symptom of the increased Ca.

So, we can start with a much lower container media pH than than we could a mineral soil pH and still have perfectly healthy plants. The lower starting pH allows for a greater (mostly) Ca presence in the soil than if we were trying to carry an 'ideal' mineral soil pH over to container culture. As long as the pH is reasonable, and the presence of Ca/Mg/bicarbonates is reasonable, no insoluble compounds are likely to form from the fertilizer solutions we supply, and the plants will readily take what they need from the soil solution - as long as it's there at a favorable o/a level and in favorable ratio. Since the o/a presence of nutrients in container media is low, low pH doesn't present the Al issues it would in mineral soils, though there would be some Fe concerns in bark-based soils because of the potentially high Fe:Mn ratio in conifer bark. It's interesting that I just read a study about growing plants that seemed to like high pH soils because of their inability to tolerate Fe, but when Fe levels were monitored and kept within tolerable limits, pH from 4.0 - 8.0 had almost no effect on growth rates

I suppose this (the pH thing) could go on the list with other clear delineations between how things work in the garden vs in container culture.

Al

container media

Al