Well, we can start with some quick and dirty definitions:

Chelate: Complex molecules that can bond to positively charged ions (cations for short) and can also be taken up by plants. For example if you add iron sulfate and a chelating agent, the soluble salt (iron sulfate) will go into solution (be dissolved) and iron will bind with the chelating agent, allowing it to stay in solution and available to plants rather than binding with oxygen to make highly insoluble iron oxides.

Colloidal: Describes soil particles that hold a negative charge (primarily organic matter and clay particles). The negative charge allows positively charged ions to be held to the surface of the particle.

Elemental: Atoms or groups of atoms comprised of one element from the periodic table. For example a single oxygen atom is considered elemental. Two oxygen atoms that are connected would be called O2 (which we breath) and is still considered elemental.

Mineral: For our purposes:
1) crystaline structure that makes up the "dirt" portion of the soil and is highly insoluble.
2) Soluble non-organic molecules (organic molecules being based on a carbon chain with other stuff stuck to it) that are available to plants as they go into solution for uptake. Nitrate (NO3) and sulfate (SO4) are examples. (This is why they say that as organic material breaks down it "mineralizes". Plants can only take up nutrients in their mineral form. A plant trying to take up an organic molecule would be like us trying to eat a watermelon through a straw).

Now to the other stuff. Reading through your post it sounds like your greatest concern is to provide micronutrients. I wasn't familiar with Azomite so I took a quick look and boy-howdy are there a lot of minerals in their guaranteed analysis. However, the method they mention to determine those values is Fusion ICP/MS. If the lab techs were the crew of the Starship Enterprise, that method is what happens when you set phasers to "kill". You just melt whatever you're testing down to a soup. Very little of what they list would be available to plants. For the most part you would just be adding "dirt".

Same goes for the rock dust. You can have oodles of any nutrient you care to name but if it is locked up in a highly insoluble form then the plants can't use it. Even adding a chelating agent wouldn't help because the materials have to first be soluble enough to go into solution in order to be chelated.

I'm not sure if that hit the nail on the head. Was that what you were looking for?

Oh yeah. Nutrients don't need to be chelated to be available. When chelates are most useful is when the reaction of the soil is alkaline. Different minerals are soluble at different pH levels. In alkaline soils, a downward pH adjustment is often all that is needed to free up nutrients.

What you have to remember about micronutrients is that if plants need them, then you can find them in plants - in other words, in your compost pile.

Silicon dioxide (aka silica or quartz) is the main ingredient in glass and the most abundant mineral in the earth's crust. Now, there are a lot of different minerals in rocks, but most of them have silicates in one form or another. I would be surprised if FL sand did not have much silica. Silica doesn't do anything for your plants really, as a nutrient, but provides the mineral structure of the soil. I don't see how adding silica to a sandy soil is going to do anything to help the garden. If you wanted more silica just buy some quartz sand. But you already have lots of sand!

The montmorillonite you mentioned is a type of clay. A little clay wouldn't be a bad thing to amend sandy soil with, but I wouldn't get it shipped from very far. There has to be a source closer than out West. I hear Georgia has some clay... :-]

But, again, compost.

Excellent points, Tox.

Thanks, Garb, that is helpful. I am not dealing with alkaline soil anywhere.

Let's see if I get it: one of the 'cations' is Ca. So calcium carbonate, for example, is a chelate? I know calcium sulfate is a salt, is it also a chelate?

One reads about chelating urine. This is what apparently happens when one stores urine in an air-tight container, and it has been my observation that such aged urine has more effect on plants than fresh, when applied as a diluted fertilizer in water. So if i am understanding it properly, the NPK in fresh urine can't bond to positively charged ions but in aged urine it can?

Regarding ph: are you familiar with the writings of Charles Walters? In one of his books I read recently he talks about how in soils over 7 the natural action that breaks fresh minerals out of compounds stops. That is why they have to use acidulated salt fertilizers on such soils. So accordingly it is a terrible mistake to lime soils to the neutral point, since not only will Ca likely be out of balance with Mag and K and S, but all the traces will be "locked up". That seems to go along with what you are saying about chelates and alkaline soil.

I will reserve judgement on the azomite until I can run some somewhat isolated tests with the small quantities I have presently.

How it was explained to me was that very old (millions of years) weathered sand has nothing left but silicon oxide. The plants need fresher stuff.

This idea that decomposed matter from plants grown on soil that is low in some micro-nutrients can then supply the missing micro-nutrients seems like a magic trick. How does that work? let's use the example of the florida sand, where my test showed less than .02 ppm of Boron. So I take a bunch of the plant matter that is growing there, compost it, and then expect the compost to raise the ppm B to acceptable levels? I think even if I religiously composted the produce of 5 acres of grass or millet or some other suited crop and concentrated the resulting extremely well broken-down compost into a far smaller area ppm B would never raise enough to sneeze at. It is an effectively missing element. Same goes for most of the other traces, they are not just a little deficient such that one could play the game of robbing the traces from a much larger area to raise them in a little garden. And where is the long-term gain in that?

Also, the term 'clay' I don't think says much about a material's mineral content, only the size of the particles.

I agree with your assessment that a soil lacking in certain minerals can't be remediated by applying vegetable composts that originate from the same soil - like some sort of immaculate conception. That is the advantage of sourcing composting ingredients from as many soils as possible.

You may want to check with FEDCO regarding Azomite, which may at least save you some shipping costs

Before you spend $$$ on long distance trucking, you might want to check with Fedco up in Maine. Their website is not the most elegant, but they have one of the best stocks of organic ingredients (including some of those you mentioned) in the Northeast. They sell in large quantities and their prices are excellent - I only wish they were closer to me in the Midwest. Here's a link to their site:

Here is a link that might be useful: Fedco - Organic Grower's Supply

Let's see if I get it: one of the 'cations' is Ca. So calcium carbonate, for example, is a chelate?
Actually, no. Chelates are very complex molecules that the plants can metabolize. Most are synthetic and have very long scary names but go by their initials like EDHA, DTPA, and EDDHA (from order of least to most effective). These work pretty well but are actually kinda nasty chemicals. I am not above using them when options are limited but I try to avoid it when possible.

Some others that are not synthetic are lignosulfates and a couple of others based on citric acid, I believe. I personally haven't found those to particularly effective in alkaline soils.

Regarding ph: are you familiar with the writings of Charles Walters? In one of his books I read recently he talks about how in soils over 7 the natural action that breaks fresh minerals out of compounds stops.
No, I'm not familiar but I would disagree with the statement. Most manures start out alkaline (pH greater than 8.0) and lots of mineralization occurs as they decompose. As that process occurs the pH shifts towards neutral but along the way, nutrients are being made available for plants. However, the availability of those nutrients will vary with the pH. That's something I deal with almost daily.

One reads about chelating urine. This is what apparently happens when one stores urine in an air-tight container.....
To be honest, I'm not sure what to tell you about jars of old pee. There might be something to it but I don't know.

This idea that decomposed matter from plants grown on soil that is low in some micro-nutrients can then supply the missing micro-nutrients seems like a magic trick.
Absolutely right. The compost that you make on nutrient deficient soil won't improve the nutrient status of that soil. I guess that maybe if you had something that was aggressively deep rooting like grapes, they could mine some nutrients from lower in the soil profile and you could pull nutrients up that way but...I dunno. Maybe that would make a nice thesis for some post-grad.

Also, the term 'clay' I don't think says much about a material's mineral content, only the size of the particles.
Clay is a very general term and there are lots of different types of clay. But the type of clay (i.e. the montmorillonite that you mentioned) does. Also, when you say "mineral content" do you mean what makes up that actual "dirt" particles or are you talking about plant available mineral content of a given soil?
Keep in mind we are talking about clay in a very strict sense. A soil classified as a "clay" according to USDA classification standards can also contain significant amounts of silt and sand. In fact, I've never ever once seen a sample of "clay" with 0% silt and 0% sand.

To add a little more to the "compost" paragraph. Compost would be a great way to improve the amount and availability of micronutrients in your soil. However, it needs to be made of something other than plants that were grown in nutrient deficient soils. In other words, you might have to truck some in.
By the way, did you mention your soil pH?

That is just my objection to buying/hauling compost or manure, which I have done plenty of in the past. How does one know what soil the ingredients were grown on? Given that most soils everywhere are deficient to some degree, one has to question whether compost is worth the hauling in the long-term picture. That is fuel and or money that maybe could go to buying and hauling something that would more certainly help to correct the deficiencies.

So that is the question for me: what is most worth the expenditure? If I have x number of bucks to spend on an acre of amendments, five years down the road will I be better off with this vs that or something else again from my inputs this year? I think the difference in that picture could be very large.

I have various plots with ph ranging from just under 6 to close to 7 in the one I have been using the longest. Most are right around 6.

I haven't seen a lot of success in regards to increased nutrients with the mineral "amendments" and considering their low solubility, it doesn't surprise me.

However, adding a clay material would improve your nutrient holding capacity. When you put in a source of micros, they'll be available to the plants longer. Typically, I don't advise mixing sand silt and clay for reasons I've mentioned a lot of times on these forms. But hey, you shouldn't follow anyone's advice to the exclusion of everything else you know. Mine included. If it seems to add up to you, go for it. You know your land better than I do.

Chelates are very expensive on a large scale and with pH values from 6 to 7, all you need to do is get the nutrients in there and they'll be available. No chelating necessary.

In regards to compost, some of the big suppliers actually run regular analyses and they can tell you exactly how much of each of the majors and minor will be immediately available as well as what will become available over time as it decomposes. If you find a place that does that sort of testing regularly, I'm sure that they would be happy to share it with you. It's actually a marketing tool for them.

By the way, do you know exactly which nutrients are low and by how much?

Wouldn't you be much better offer adding purified micronutrients - if that's your goal? Azomite (or whatever unrefined mineral source) may have a smorgasbord of trace elements, but you're buying and trucking a lot of useless "rock" along with it. Using sulfates (copper, zinc, manganese, etc.) would be a much more efficient approach. Even for an acre, the cost would be modest.

Right, sulfates added with OM. I did some of that last year, and will do some more this year, for example, sul-po-mag mixed with humate.

And you have struck on the crux of the matter, I would much rather use rock than synthesized products, but how much of the weight is useless? The implication in this thread is that silicon dioxide is useless filler. But is it really? Weathered quartz pieces and silicon dioxide aren't quite the same thing, otherwise one wouldn't need cement to make concrete.

Garg, another thing that I don't like about the guaranteed analysis of the azomite is the appearance of some of the minerals in oxide form. Curiously, the fellow who sold me the stuff (a retired extension agent) told me that plants cannot take up oxides. He also says that they don't take up sulfates well. What they like is organic compounds. I think the idea is that if one adds the azomite or other "active" rock dust to soil with plenty of OM, or if lacking also add a form of OM, together the minerals in the dust are fairly quickly converted to organic form.

If the guy told you that plants take up organic compounds he was wrong. Remember, plants can't take up organic molecules they have to be mineralized before the plants can take them up. Nitrogen has to be either nitrate (NO3) or ammonium (NH4), Phosphorous has to be P2O5, potassium has to be K2O. Sulfur has to be sulfate (SO4) etc...

When he said that plants don't take up oxides, he probably mean that oxides are highly insoluble. Remember back to my chelating example where I mentioned that chelates bind to the iron before it can become insoluble oxides.

Sulfates are a lot more soluble than oxides. I would suspect that saying that plants don't really take up sufates was either just part of the sales pitch or he really didn't quite understand what he was saying. Because yes, plants don't take up "sulfates" in the form of sulfate salts but sulfates go into solution relatively quickly and easily, allowing the nutrients to become available. Potassium sulfate, iron sulfate, calcium sulfate, magnesium sulfate, etc. all have varying solubilities but are plenty soluble enough to allow the nutrients to go into solution and become available to plants.

If you do go the sulfate route, keep an eye on your pH because some can shift your pH downward pretty significantly. That's especially true with iron sulfate in a sandy soil, which has a lot less buffering capacity than a heavier soil. You don't want to push your pH down too far or you'll start decreasing nutrient availability that way. But, if your cautious, sulfates can be a way to go. Copper, manganese and zinc are needed in such small amounts compared to iron that I don't think you'd have much of an issue with those. In regards to calcium sulfate (gypsum) there is no issue regarding pH change.

if one adds the azomite or other "active" rock dust to soil with plenty of OM, or if lacking also add a form of OM, together the minerals in the dust are fairly quickly converted to organic form.
That, my friend, is sales talk. Those types of materials are highly insoluble and require huge amounts of time to break down. The dust looks like really small particles to you and me but it is still just rocks physically broken down into smaller chunks. When discussing plant nutrients, we're talking about tiny polyatomic ions and atoms; stuff on the electron microscope scale. The size difference between plant nutrients and those bits of dust is like a baseball next to a cruise ship. Even at that stage they have a long way to go to break down to the point that you have individual atoms to work with. Adding organic matter along with them will not do anything to improve their innate solubility. Think about this. How quickly do rocks decompose in a compost pile compared to sitting out in the open? That's all the dust is. Very tiny rocks with all the same chemical and physical properties of that type of rock but on a small scale. And, as stated, plants need their nutrients in mineral form...

So what is your viewpoint on the idea that microbes "break" the nutrients out of the dusts in a form available to plants on a much faster scale than natural weathering?

And to support the microbes ones needs sufficient amounts of OM and/or clay particles.

BTW, the one-acre plot I am expanding into right now, long-time old grazing land, has the typical problem with light soil that has been chronically limed with dolomitic limestone, too much mag to ca and k, at least according to the Albrecht balance. Of course Umass had no problem with it. They also said on the test that micronutrients are all within normal range even though several of them were clearly low by their own paradigm! WTF? My co-farmer got the test, I would have used an Albrecht paradigm lab.

Unfortunately suppliers here only carry dolomitic lime, so I had to use it, but I also used nearly as much gypsum. The ph was 5.9, Ca 584ppm; Mag 101ppm; K 46ppm; Sulfur 10ppm. P was 5ppm which must surely be falsely low due to time of year. B low, Mn low, Copper a bit low. Iron tends to be adequate to high everywhere around here, which no doubt suppresses the already low Mn.

My view is that it doesn't happen they way they say it does but it sounds good so sales people keep saying it. It's like repeated claims that this product or that product "neutralizes" salts or that there are in-line filters that will "align" your water molecules to make your water penetrate the soil better.

There is some of that going on with a limited number of mined minerals such as rock phosphate and mined potassium sulfate and calcium sulfate. There are a few fungi like some in the generas Glomulus and Aspergillus that play a role in the increased availability of a few of these mined minerals that are commonly used as fertilizers. (That's why they're commonly used as fertilizers. Because it has been observed that through multiple avenues, the minerals do become available to the plants.) The fact that some microbes are a factor in the break down of some minerals is then extrapolated out by savvy sales people to imply that there is a virtual army of microbes out there that will break down any rock. That's simply not the case.

So let's see if I am grasping part of this:

It is often said, as you are saying, that the minerals in rocks leach out extremely slowly, too slowly to be much if any help in the time scale of growing crops. Yet we all know that calcium-bearing 'rocks' are very useful to growing crops. And we all know that the more finely calcium-bearing rock is ground up the better it works. From that it seems to stand to reason that other types of rock bearing other minerals would leach out better if ground as fine as possible.

What you are saying is that something like limestone is not comparable to something like granite or basalt. The former is a proven fertilizer, and the latter are known to science to be totally inert, regardless of particle size. Is that correct? Montmilloronite clay is yet another material. What do we know about it as a fertilizer? Probably next to nothing, from a peer-reviewed perspective. It might be very useful, or it might be mostly not worth hauling.

I stand corrected on the implication in my post that compost will improve micronutrients - obviously they won't be there if they weren't there in the first place. That was not exactly what I meant but it was late in the day!

No, Tox has not invented a new kind of alchemy.

What you are saying is that something like limestone is not comparable to something like granite or basalt. The former is a proven fertilizer, and the latter are known to science to be totally inert, regardless of particle size. Is that correct?

Yeah, that's pretty much the jist of it. Think of it this way. If all rock particles could be broken down the same way, you wouldn't have any mineral component to your soil because that's what sand and silt are. Broken down bits of rock; sand being bigger than silt. Yes, grinding the rocks to dust will speed the process but maybe you'll be looking at 850 years instead of 5000.

Looking at your data, I would agree that your Ca and Mg aren't out of wack and both look to be sufficient for a sandy soil. I have seen antagonistic calcium deficiencies with Ca Mg ratio less than 2 but your looking at 5.8 to 1 and I don't know many people who would even blink at that. For what it's worth though, I rely more on sufficiency than ratios in most cases anway. Here's a little article from Iowa state with some information and additional links in the document that provide more discussion on the topic. Cation ratios.

As far as liming goes, I don't think that the dolomite will hurt anything but if it makes you feel better, 5.9 is a little low but I think you could get away with not liming as long as you don't regularly use acidifying fertilizers.

They also said on the test that micronutrients are all within normal range even though several of them were clearly low by their own paradigm!
That's pretty common. A lot of labs have a computer program that will assign qualifiers of "high" "medium" "low" based only on the level of the nutrient. Then, if the people working there know what they're doing, they'll take into consideration other factors. My guess is that their computer program spits out "low" and the person reviewing the data said not to worry because the values don't need to be as high in a sandy soil to be sufficient.

In regards to boron, do you know what the level of that nutrient is in your water? Lots of irrigation sources contain enough boron to satisfy plant requirements for that nutrient. In those cases, it can look like boron is low in the soil but you have a constant feed and the plants do just fine.

The P could be really low or it could just be that the method used to extract phosphorous doesn't work well with your soil type. That nutrient is particularly finicky from method to method.

Yes, grinding the rocks to dust will speed the process but maybe you'll be looking at 850 years instead of 5000.

I've had colloidal phosphate show up on my soil test within a year and hard rock phosphate within two years. I've also used stuff like Azomite, glacial rock dust, greensand etc. with positive results. There's little scientific research on on the "whys," but there's a ton of anecdotal evidence that suggests a positive effect on the soil.

Garg, When these soil test results come back stating for example, 581 ppm, is this supposed to represent the available or the total quantity of that mineral/element?

Right, rock phosphate was one of the ones I mentioned specifically that it does work for. I believe that there's a little something to greensand as well. As far as most of the other stuff, I've seen a number of "rock dusts" used with no benefit to nutrient status in the soil. On the contrary, I've never once seen the results that were promised actually come to fruition.

The problem with anecdotal evidence is this. If you apply multiple strategies to a growing area without strict controls, it's tough to say which one or which combination actually improved (or was detrimental to) plant performance. Also, lots of the "anecdotal evidence" comes in the form of either overt, thinly veiled or cleverly disguised marketing materials. But like I say: I ain't the dirt cop and I don't know everything. If it's working for you, go for it.

The majority of extraction methods do their best to approximate the amount of the nutrient that is actually available to the plants. However, that is tempered with years and years of studies and observations comparing the levels of nutrients as measured by a given methodology and how plants respond.

For example. Let's say a soil test in which magnesium was extracted via Mehlich 3 extract comes back at 500 ppm (aka 1000 pounds per acre) and the data sheet says "sufficient". Does that mean that precisely 1000 lbs. of available calcium can be found in 1 acre furrow slice of that soil? No, not really. It'll just be in that neighborhood. (and anyone who claims that they have a test that can do that precisely isn't giving you the whole story) That approximation is used in conjunction with the fact that it has been observed time and again that when calcium is measured in a soil via Mehlich 3 and is found between this many and that many ppm in this particular soil type, plants generally do not show signs of deficiency or excess.

I had a Mehlich 3 test done a while ago on a very similar soil at the same time of year and it gave 43ppm for P, while another umass test for a field that is well known to be greatly superior to the other two, and the degree of production and the predominant weeds agree, gave low P.

So I think the umass test done during the winter greatly understates P.

Hi guys, great thread but it is way beyond my education level. Just a quick question. Would it be reasonable to use tooth decay as an analogy for how decaying organic materials can "dissolve" (bad word but I can't think of a simplistic word that describes what I am trying to get across) minerals? We know the acid released from the bacteria in our mouths can "dissolve" tooth enamel so could that be a description that high school drop-outs like myself can wrap our brains around?

Lloyd

Lloyd, I think that is what C.Walters and Albrecht were thinking. The soil solution needs to be slightly acidic to help leach nutrients from the rock minerals.

Garg, I don't have any water tests at all. I mostly use captured rainwater in my home gardens and for the acre site I referenced earlier there is no irrigation. Some sites that I am allowed to use in other fields get irrigated with well-water, but I have no control over amendments there in any case. In florida I have well-water which I ought to get tested for minerals.

Here is an interesting statement I found on a Scottish website which does a good job of graphically explaining John Hamaker's glacial cycle theory in terms of planetary fertility. Do you agree at all?

"Dr. D Supkow PhD, has degrees in geology from Rutgers University and the University of Maine and a PhD in hydrology from the University of Arizona. In his paper on the "control of CO2 build up and the greenhouse effect" in"RemineralizeTheEarth"*,issueno.7-8,1995,Dr. Supkow estimated that in order to keep atmospheric carbon stable at today�s level, 0.8 - 3.2 tonnes of rockdust would need to be applied to every acre on Earth, every year (apart fromAntarcticaandGreenland).Hesays,"Whenrockdustis applied to the land, the calcium and magnesium content combine with atmospheric carbon, forming carbonates".

Hoo wee. I don't know nothin' from carbon sequestration.

But yes, there can be some calcium and magnesium carbonate formed (depending on the parent material of the rock, of course) because CO2 in combination with rainwater makes a weak carbonic acid. That's why statues' detail starts to smooth out over the centuries. So yes, there will be some f that going on. But again, it would be very small amounts.

Also, he may be saying: "We see a rise of 'this amount' in CO2 every year so the chemistry works out that you would need 'this much' rock dust to neutralize it." But, can you realistically expect that much rock to be dissolved by rain water every year? And how much calcium carbonate and magnesium carbonate would the result in? His numbers would be interesting to look at but I would suspect, not a whole lot in regards to plant nutrition.

I think that John Haymaker's thinking was that the rock dusts spread over both forest and fields would improve vegetative growth enough to suck up enough CO2 and sequester enough carbon to hold CO2 levels down. He tried it on his farm and listed the improvement in growth not in decades away but right away.

Wayne, I think you are correct, that was Hamaker's solution to global warming. If Garg's viewpoint is correct then no amount of making and spreading rock dust will prevent run-away global warming and subsequent re-glaciation.

FWIW, the weathering of rock minerals which takes carbon out of the air is supposed to be a primary driver of glaciation. The Himalyan mountain range is the big player in that game. I guess the question is, do we have enough fossil fuel left to grind up enough rocks to increase the rate of weathering and suck up enough carbon? While, not unimportantly, growing enormous amounts of excellent foodstuffs in the process.

If Garg's viewpoint is correct then no amount of making and spreading rock dust will prevent run-away global warming and subsequent re-glaciation.

Keeping in mind, of course, that Garg is Waaaaay out of his comfort zone talking about carbon sequestration and atmospheric conditions.

Great thread & it is easy to understand.
Is Montorillonite better then sodium bentonite(drill mud)?
If so, why?
Can I buy it under that name or is there a brand name?
Anything I should know before applying the Montorillonite?
I will do a search, but Garg seems to have most, if not all the answers.
Thanks, pnbrown & Garg.

Regarding "rock-like" materials and how can we empirically know if they have any value as fertilizer, which is the main point of this thread.

Salts look like fine sand, or small bits of gravel, yet they dissolve in water on some fairly short time scale. Table salt dissolves in minutes, while the chips in sul-po-mag take a lot longer. Something like calcium sulfate visibly changes when put in water, as does the micronized azomite. Calcium carbonate seems very inert but we know it is not. Greensand seems very inert but there is too much evidence for it having a fertilizing effect to think it is completely inert.

If we add to the mere solubility of a material the potential action of living microbes ( there is little doubt that an active soil receives the benefit of lime more quickly than a dead soil, for example) then I don't think a material can be dismissed simply because it is a "rock". We must test it in various situations.

I am gardening on land that will be left to my children & hopefully their children.
So if the "rock-like" material will work or dissolve in the next 50 years then I would put in my garden.