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Ch. 2 Classic Soil Science

Greetings!

Opening up the Second Chapter discussion.

What parts of this are you strong on? What do you have questions about...

Any surprises?

HG

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On page 31, I learned I am not crazy!
...Think of the end product of composting. This valuable material is humus
:P from now on I call it AHT, or aerated humus tea. that way it includes humus not derived from composting.

Question: on p. 36, he calls for water softener in his silt/sand/clay test. I've always just used water. So why the softener?

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I would asssume to stop colloidal action from sticking clays to silt, but we'll have wait for word from the author to be sure...

HG

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I think the water softener must hold things in suspension long enough for the layering to occur. I read Toil's post and thought, oh I can do it without the water softener. I don't keep any around the place. So I went out and tried it. Despite much shaking, as soon as I set it down, everything immediately dropped out, so not much layering.

Didn't find this chapter as exciting. The most interesting part is that I've "always" known that sandy soil drains water out very fast and clay soils hold water. Now I know why! Spaces between the larger sand particles are too big for capillary action to occur. Fine clay particles have lots more surface area for adhesion and smaller spaces so hold lots of capillary water. Way cool! And who knew there were three kinds of water in the soil, gravitational, capillary, hydroscopic?!

The part on CEC's and pH served mainly to remind me how complex all this is ... so the root hairs are simultaneously giving off and taking up anions and cations. Interesting.

On to bacteria... I always like it better when we are talking biology instead of chemistry!

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Me too RBG, and Jeff too, I suspect, but you have to have some key elements now to get where a lot of the chemistry fits in later. CEC is really crucial and is the main reason why I am always sure to let people with clay soil know how good they have it (once they get the soil back to good). Sandy or rocky soils are much harder to get to a happy place, but with good humus and biology, clay soils can be some of the best on the planet...

HG

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I mentioned elsewhere that I'm thinking of adding some sand to my garden beds this year (in fact I started to last fall). The "way my root vegs come out" that I alluded to is that they come out, well, mucky: Covered in sticky mud or fine silty stuff that wash off as mud. I think the loam ratio described in Chapter 2 confirms that I'm on the right track.

Can someone break down the pH thing a little bit more? I mean I knew it ranged from 1~14, low pH of 1 being very acid and high pH of 14 being very alkaline and 7 being neutral. I know what kind of plants prefer lower pH soil and what likes higher pH/limey soil. I know the usual things to add to soil to lower pH or raise pH.

However, I could *not* explain when asked "What does pH mean?" (+H ?) or "How pH gets to be 1 or 7 or 14." to my kids. I read up a bit on it, and had to admit I was still a bit stumped. Read Ch. 2 and :idea: lit. I *think* I get it now, but I still don't think I can *explain* it. (Which, by definition, means I *don't* get it. :roll: )

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pH is realy a measure of [url=https://www.miamisci.org/ph/hoh.html]how a compound reacts with water[/url]... [url=https://www.miamisci.org/ph/hhhoh.html]some more strongly, some more weakly[/url]

Check out [url=https://www.miamisci.org/ph/hhoh.html]this table[/url]

Biological activity tends towards acidity, but that is oversimplifying; actually bacterial side pushes towards base, fungal side pushes towards fungal. But a true soil succession moves towards a more fungal, generally more acid soil. You can see the early succession stuff, more mineral on the base end, and the plants on the other... As the soil becomes more acid, more nutrient is released from the parent material. This suits some plants well, and some poorly; weeds do well in more base bacterial soils. Evergreen needled trees like an acid soil with a lot of fungus...

I am blending chemical and biological explanations, but that's because that's what happens in Nature; biology and chemistry overlap. Perhaps my understanding isn't all it should be either, but I do not worry much about pH in an organic system as I am balancing biologies and that balances pH. Trust but verify...

HG

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pH comes from the German potenz Hydrogen, the potency or potential of the hydrogen. That means it's a reciprocal correlation- the more Hydrogen ions, the more acid, so the lower the pH. The H+ ions get bonded with Cl- ions to form HCl, hydrochloric acid. So you can see how the more of that you have the more acidic. pH 1 corresponds to a .1 molar concentration of HCl. pH 4 corresponds to a 0.0001 molar HCl concentration. (Remember from high school chemistry a mole is Avagadro's number or 6. something x 10 to the 23rd molecules of whatever it is .)

I don't know if this helps any-- it's the chemistry answer, not the biology one.

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yes it does. thanks for jogging my memory.

I don't think biology is more important than chemistry. That's a simplistic view. They are just different.

But biology is the one we use to read and manipulate a natural garden to our ends while improving our world at the same time.

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Indeed the two are interelated in an inescapable way.
But biology is the one we use to read and manipulate a natural garden to our ends while improving our world at the same time.
Couldn't have said it better...

And thanks for the pH primer RBG. Good stuff!

HG

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Thanks everyone! Now I just have to digest it all. Really, I have a better idea than before. It just hasn't "clicked". Rainbow's numeric answer helps to visualize it better, as do HG's excellent link and the molecular representations.

What can I say? My chem lab grades were never very good -- in my lab reports, I dutifully wrote down what was SUPPOSED to have happened, and described in detail how in my experiment, it DIDN'T. :roll: I'm an excellent cook, however (or so most people say) 8) I'm a horrible chef though, because I can rarely reproduce a recipe again. :wink:

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Hi gang,

I have been lecturing around the country and not been able to log in.
Glad you are all into chapter 2. This is the most difficult chapter to get through. I have to tell you that this was the chapter I did not want to write. Ugh.....struggled with pH and CEC and soil types all my life and then it was my turn to give it a go......However, the soil is the stage for the characters in the book and you have to be exposed to this stuff. It will all come together in a few more chapters, that is for sure.

pH: In organic gardening it is the biology that creates the chemistry. That is the way to look at it. Later you will learn how to manipulate the biology to change the chemistry. Don't get too hung up on pH....all you need to know is that over 7 is basic and under is acidic. Really, it is as simple as that.

The one area I think I really nailed is the couple of paragraphs on CEC. Again, you don't really need to know too much about it, but it is interesting stuff that I had always struggled with. Good thing I didn't try and get into Brix numbers, huh!

Again, this is THE difficult chapter and it has a whole year's worth of soil science classes in it. Read it, and then move on. I pull what you need into other chapters and go over it again, so don't sweat it too much.

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Thanks so much Jeff!

See told you guys not to worry about the chemistry stuff too much... :P

...but ready to talk Brix any time you are, Jeff. I think it may be a more important number than any of these others we are discussing, but I'm no expert. And I tend to wander off topic which is why I don't write books... :roll:

(yet)...

But Jeff does, and this is a good one, eh? Anybody ready to move to Chapter Three? Sing out with the opinions...

HG

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Hi Jeff, if you can, I'd love to know if I can do the jar test without the water softener.

Thanks so much for taking time out to do this.

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I just finished reading chapter 5....

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We can move on. I'm reading Ch. 4. If something else relevant to earlier chapters come up, we can always post back. :wink:

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ditto, but I didn't want to say it.

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I'm rereading Ch. 4; one of the new ones and a weak subject for me...

But we are getting ahead of ourselves. Anyone NOT ready to move ahead to Chapter Three? Any other takers for Chapter 2? You can always post here with questions on soil basics, but a lot of folks do seem to be surging ahead...

HG

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well I would like an answer about the humus thing. I'm as confused as ever.

but that's up to Jeff.

In a perfect world, it would be cool if everybody did the jar test and reported back with a picture or just words. But even if we get a couple we can talk about them.

I mean, the subject is kinda boring (no offense Jeff!), but it might be because we are talking abstract instead of looking at something.

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I am not done with chapter 2 yet but I don't mind if you move on. I'll catch up. :wink:

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Seeing no other objections, I shall post for Ch.3 this evening...

HG

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I'm just starting chapter 8 I was kind of wondering what happened to this till I finally checked. :oops: 8) Carry on if you will this is definitely a book to reread. Great job Jeff.

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This is the sample


[img]https://i929.photobucket.com/albums/ad137/toilpics/soiltest/DSCF0001.jpg[/img]


here is a slice

[img]https://i929.photobucket.com/albums/ad137/toilpics/soiltest/DSCF0002.jpg[/img]


and this is enhanced for detail.


[img]https://i929.photobucket.com/albums/ad137/toilpics/soiltest/DSCF0002_2.jpg[/img]

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So with or without softener, toil?

HG

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without.

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soil sample b

[img]https://i929.photobucket.com/albums/ad137/toilpics/soiltest/DSCF0021.jpg[/img]

[img]https://i929.photobucket.com/albums/ad137/toilpics/soiltest/DSCF0023.jpg[/img]

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This was a pretty interesting chapter for me (don't mind all the chemistry stuff). I liked learning about the various types of in-soil water and their characteristics.

It was also interesting to find out that is is merely particle size, and not elemental-make up, that largely determines if it is sand, silt, or clay. And that sand and silt don't have an electrical charge, so they play a lesser role in determining the CEC of the soil.

I also enjoyed the science behind the CEC of the soil. It seems like we could say that plants that prefer nitrogen in the ammonium form wold get a better supply in good organic soil since this is the form that had a positive charge and is locked up by the soil. However, it would seem that nitrates, which have a negative charge, would be in slightly less supply since they appear to be more subject to reaction and leaching because of them not being locked up in the soil. However, it is nitrogen oxidizing bacteria that would create the nitrate, so perhaps they store it as well. What do you think?

On the topic of Ph, I thought it to be very clear about what Ph is and how it is determined (although, as you all have previously demonstrated, it appears to be a little more complex). It states that is is a measure of how many hydrogen ions are in a solution. Now, on page 41 it seems to directly contradict what RBG said about pH: "The pH tells the concentrations of hydrogen ions (H+, a cation) in the solution being measured. If you have relatively few hydrogen ions compared to the rest of what is in solution, the pH is low and the solution is acidic. Similarly, if you have a lot of hydrogen ions in solution, then you have a solution with a high pH, one that is alkaline."

RBG said that high levels of hydrogen denotes acidic soils and the book said high leaves denote basic (alkaline) soils. Which is correct?

I did not get a chance to try the soil layer test, but I'm glad someone did......now I need an interpenetration of it. How would you rate the particle levels in the soil, Toil? From my view, it looks like 40% sand and silt and about 10 or 20% clay :?:. I'm having trouble differentiating the layers :oops:

Great discussion on this chapter, everyone.

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I don't know where my copy of the book is off hand to see what is going on there and if there's anything in the book to resolve the contradiction.

But here's the Wikipedia explanation of pH:

"In a solution pH approximates but is not equal to p[H], the negative logarithm (base 10) of the molar concentration of dissolved hydronium ions (H3O+); a low pH indicates a high concentration of hydronium ions, while a high pH indicates a low concentration. "
https://en.wikipedia.org/wiki/PH

If the author of the book said otherwise, then he just got it wrong.

Hydronium ions incidentally are H30, which is how hydrogen exists in water. Wiki: "Hydrogen ions in water can be written simply as H+ or as hydronium (H3O+) or higher species (e.g. H9O4+) to account for solvation, but all describe the same entity." So that is not the difference.

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Well, RBG, after reading several sources and looking at it closely, you are clearly correct and the section on pH clearly got in backwards.

I think the trouble may lie in the fact that pH is a negative logarithm of the concentration of hydronium (hydrogen). I believe this means that it increases as the concentration decreases. I'll bet that more than likely, the article assumed that it was a direct measurement of the ion concentration. That is, it assumed pH increased as the concentration increased. Of course, the author could have just as easily confused the acid/alkaline properties of the compounds, but I think the former is more likely to have happened.

If HG was here, he'd probably kick both of us and tell us we should be focusing on the biology and not worry about the chemistry technicalities. I'll be the first to admit he'd be right, too.

However, I can't resist a resist a deeper look when presented with a discrepancy like this (and after all, this chapter is titled Classic Soil Science :wink: ). I'm glad I did, since now I've got an even better understanding of pH :D.

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Concentrate on the biology. It'll adjust the pH to where it needs to be anyway... :P

And Hydronium isn't hydrogen, it's H3O. Reduce the H3O and we get water and a free hydrogen. So an increase in hydrogen and a decrease in hydronium? Could this be our discrepency?

I dunno... just pay attention to the biology... :wink:

HG

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rainbowgardener wrote:

Hydronium ions incidentally are H30, which is how hydrogen exists in water. Wiki: "Hydrogen ions in water can be written simply as H+ or as hydronium (H3O+) or higher species (e.g. H9O4+) to account for solvation, but all describe the same entity." So that is not the difference.
It is how hydrogen ions exist in water. H+ ions quickly bond to become H30, and "higher species." That is not the discrepancy. He just made a mistake.

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Interesting! So the publisher's people don't "edit" -- I.e. have someone check a manuscript over -- for technical errors? I mean a scientific work -- the original science might be the author's but there could still be "typos" and "spelling/grammatical" errors, couldn't there? Isn't that what science editors do? (I've no idea) Hmm... I wonder if I know someone who would know that sort of thing.... :?:

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Apps, I've been thinking about that as well. Perhaps, as we all know, pH is such an intricate subject that the editors didn't even want to start picking apart the technicalities of it and just took the authors at their word (Jeff even said that this was a chapter he wasn't enthused about writing)? Just a guess.

Logically, this should have been double-checked and corrected, however, logical things don't always happen :roll:. Like HG said, the biology makes things how they should be, so I suppose we shouldn't worry too much.



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