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Volcanic rock, any nutrients?

Posted by poaky1 6 Pa (My Page) on
Sat, Apr 13, 13 at 1:06

I hear about adding Azomite and other rock dusts to soil. PLEASE keep your responses simple and to the point. Those black and red colored "pumicy" rocks you can get for mulch at the big box stores, are they rich in anything besides just pumice? Is there any iron, potassium, magnesium, phosphorous, calcium or trace minerals be they good or bad like too much aluminum? There was a post a while ago about volcanic soil in a part of Italy and these WONDERFUL tomatoes grown there. I know I should test my soil before adding much more than OM, but I wonder if this stuff has any mineral content use, or is just bonsai soil additive and mulch? Don't get too scientific until after you give me the answer for dummies. I realize the answer isn't always that simple, but try to give me the simplest answer before all you get into the long version. Thank you all who answer.


Follow-Up Postings:

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RE: Volcanic rock, any nutrients?

Plants grow quite well in Volcanic Ash soils, but most everything I have seen also says if there is a lot of organic matter in the mix. But if you look at piles of Volcanic Rock you do not see any plant growth.


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RE: Volcanic rock, any nutrients?

My pure guess is that they will not leach fast enough to be useful in correcting low traces in a soil, unless it were over many years. Volcanic soil has a lot of super-fine particles which is a very different situation.


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RE: Volcanic rock, any nutrients?

The simple answer is that yes, pumice contains all of the elements you mentioned, and it does break down, but probably not at a rate that matters.

Now the scientific answer:
Pumice is a rock, not a chemical component, so it can have a range of chemical compositions, but will always contain O, Si, Al, K/Na, Ca, Mg/Fe, roughly in that order (high to low), as well as a variety of trace elements. It chemically weathers into clay minerals and quartz, making some nutrients available.

Generally, if you get a darker volcanic rock, it has more Ca, Mg, and Fe relative to K and Na--in igneous systems, Ca and Mg/Fe-rich minerals crystallize at higher temperatures than K/Na-rich minerals and produce darker rocks. Those minerals are somewhat less stable at the low-temperature/low-pressure conditions that we're used to, so they will weather more quickly than lighter-colored volcanic rocks into clay minerals and quartz. Again, it is probably not at a rate that matters much to you.


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RE: Volcanic rock, any nutrients?

How quickly did the area around Mount St. Helens recover, show signs of new growth, after the eruption?


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RE: Volcanic rock, any nutrients?

I'm in Portland Oregon and we were covered in ash from Mt St Helens when it blew. The newscasters doing 24/7 coverage, when looking for something new to say, found somebody that explained the ash was going to be good for our gardens. I think they were just trying to help us feel better about all the required repeats of washing down our cars, sidewalks, streets, and indoor floors as it got tracked in, and the daily morning ritual of having to open the hood of the car and put a fresh toilet paper cover around the air filter.

As you might guess, then we had all the arm chair experts, you know the type, gardeners that have never planted a garden but know it all, telling us over and over what wonderful magic was going to happen in our gardens. One quickly learns to just smile and nod, as any talk of facts upset them greatly and caused much screeching. ;)

As far as how the garden improved... I'm still waiting. Thirty three years so far.

This post was edited by plaidbird on Sun, Apr 14, 13 at 12:29


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RE: Volcanic rock, any nutrients?

Of course, your soil to start with is probably volcanic and maybe recent enough geologically to not have had most of the goodies leached out, so a fresh dusting of ash didn't make a noticeable difference in crop performance. Bring it out east to leached soils especially south of the glacial zone and might be a different result.


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RE: Volcanic rock, any nutrients?

If we could have huffed and puffed and blown some your direction, without the Rockies getting in the way, I'm sure if we had thought of it, we could have gotten a big turn out for the event. What a mess we had. It was only about an inch or so deep at my place, but it lasted for a very long time.

Thanks for adding to the story, I could have done a better job of telling the tale.I agree, it was just adding more of the same to our soil. We have one volcano, Mt. Tabor, right here in the city itself, an easy walk from my front door. Plus Mt. Hood ( also a volcano) is about an hour/hour and a half away. It's the one you see when they do a photo of Portland to promote tourism. We see it everyday when outside, and you would see it on our postcards.

But now that we're here, I have been wondering about the huge landslide business they are doing now, selling types of rock dust to all my neighbors. Since all rocks are not the same, I've looked up the two most popular.

Glacial Rock Dust
Ingredients: Derived from glacial moraines located in British Columbia, Canada.
http://www.planetnatural.com/site/glacial-rock-dust.html

and
Cascade Minerals-Basalt
http://cascademineralsnw.com/product_facts.html
doesn't really say what it is from what I can see.
This ??? "Buffers both high and low pH levels in soils"

I realize without soil sample results this is all just theory, but I'm not sure adding these is not more of the same, same as MT. St. Helens ? I may be missing something here.

This post was edited by plaidbird on Sun, Apr 14, 13 at 20:07


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RE: Volcanic rock, any nutrients?

Oh-oh..spoke before I double checked. Seems the Rockies were not in the way as much as I thought. Amazing.

Here is a link that might be useful: check out where the ash did drift.

This post was edited by plaidbird on Sun, Apr 14, 13 at 20:01


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RE: Volcanic rock, any nutrients?

I have been close enough to mt hood to see it in reality, as it happens. I reckon without ancient/historical volcanoes we'd have all starved to death by now, but I can imagine that being around real-time eruptions is no fun at all.

Also I would think you must be correct that volcanic soils as recent as in your region would not much need rock dust additions.


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RE: Volcanic rock, any nutrients?

I often hope it's not just me being older and set in my ways, ya know ? I read here over the years in hopes of keeping up with what might be new. So thank you very much. Boy, adding rock dust is just what they all do now. It's not just the hippy dippy's either.( not that there's anything wrong with being a hippy dippy )

I'm glad you have been able to visit Mt Hood. It's such a beautiful place. One we do take for granted too often. It's a place where we grew up going on the weekends, and continue through the years.

Now after Mt St Helens ( which still looks broken to me) , I have brief moments when I consider Mt Tabor.. if it were to blow, I'm pretty sure I'm a toastedbird. I'm older and slower now, and one of those people that always says " no..you first". Probably wouldn't make it out from the middle of the city in a mass exodus. Hope my garden comes back impressively though.

Thanks again.

This post was edited by plaidbird on Mon, Apr 15, 13 at 0:12


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RE: Volcanic rock, any nutrients?

Bearing in mind that what I have said is guesswork on my part.


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RE: Volcanic rock, any nutrients?

I remember a thread where someone (maybe even me) looked up the composition of that red pumice but I can't find it now.

One thing about your question - is that pumice rock sold as mulch any good besides as mulch? - unless it's ground to powder, it doesn't release any of its minerals very fast. So, unless you have a way to crush it, it's not going to do much.

If you can make and use compost, it's going to have (by definition) all the minerals used by plants. Unless you just don't have enough, or your soil is VERY poor, you should be OK with compost. JMHO, from the land of rich clay soil. :-]


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RE: Volcanic rock, any nutrients?

" use compost, it's going to have (by definition) all the minerals used by plants."

Variations on this theme are very frequently stated as fact. I keep asking, without getting any good answer, why would that always be true, and how would we know?


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RE: Volcanic rock, any nutrients?

  • Posted by TXEB 9a (My Page) on
    Mon, Apr 15, 13 at 18:52

There's nothing magic about volcanic rock. If well ground it can be useful as a mineral additive to soil, just like about any other natural rock deposit. There are a number of solid additives for sale that originate from powdered volcanic rock, and like most ground natural mineral additives the availability of the mineral content will be affected most largely by soil pH. Typically the dominant base of volcanic rock is silica ( same as sand).

A number of "famed" agricultural soils are known for their high volcanic mineral content, including Idaho, HI, Italy, northern CA, etc. But in those areas the essential requirements for good soil remains the same, and volcanic mineral content via well degraded deposits (think millennia) doesn't change what constitutes good soil.

Mt. St. Helens is not a useful basis for comparison, at least not in our lifetime. That was a dump of volcanic ash on top of everything, not incorporated into the soil. It's more comparable to dumping a load of very dirty sand on top of whatever was growing.

This post was edited by TXEB on Mon, Apr 15, 13 at 18:53


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RE: Volcanic rock, any nutrients?

I have read that old volcanic soils can be quite nutrient poor, like old soils in general. Other than glaciation, volcanoes are the primary way that fresh minerals important to plant growth are brought near enough the surface to be broken down over a few millennia by weather and mitigate the problem of ancient soils, as I understand it.


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RE: Volcanic rock, any nutrients?

  • Posted by TXEB 9a (My Page) on
    Mon, Apr 15, 13 at 20:46

"If you can make and use compost, it's going to have (by definition) all the minerals used by plants."

Not necessarily. I can make great compost from shredded paper and horse manure, with nothing else added. Does that, by definition, have all the minerals needed in the proper ratios for tomatoes, or peppers, or Brussels sprouts, or carrots, or ...? The minerals supplied by compost will depend upon from what the compost is built, and the amounts supplied will depend upon the rate of incorporation. The real trick with compost is the formulation, not just that it is compost.


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RE: Volcanic rock, any nutrients?

Not to mention whether or not all horse manure, or even paper, has the same mineral composition.


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RE: Volcanic rock, any nutrients?

I was at an indoor garden show this past weekend and one of the vendors was advertising this product.

Here is a link that might be useful: Volcanic Minerals Plus


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RE: Volcanic rock, any nutrients?

The old volcanos & the volcanic rock strew all over many places in New Mexico is in arid areas & doesn't seem to have been broken down much over the years in this dry, hot climate so may not have contributed much to soil fertility as it would in say, Hawaii. We have both the dark & the red volcanic rocks & not sure if there differ in fertility/composition? In the garden here I don't see much of an improvement around the rocks & the red 'scoria' crushed rock used in some older landscapes makes a stained mess when broken down!


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RE: Volcanic rock, any nutrients?

Thanks for the replies. I bought a bag of the red rock form (not crushed) lava rock to add to potting mix for house plants. I never used the whole bag. I heard about tomatoes that tasted better in Volcanic soil. It was a post on this forum. I have crushed the rocks with a hammer, which is easily done, I add it to raised beds for veggies, potting mix, when I spread shredded leaves under trees. My in ground soil has good texture but showed a need for Phos and Calcium BADLY, I got Gypsum and Bone meal. The others are in the below optimum column, but not by much. I am glad to know it is okay to use, even if it isn't SUPER GREAT for my soil, It will do no harm if I use a dusting on top of shredded leaves or done compost.


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RE: Volcanic rock, any nutrients?

Unless you actually add minerals to your compost, it won't have any minerals in it. It will, however, have whatever chemical components of minerals were converted into living tissue.

If you want to get an idea for the mineral composition of your volcanic rock, look at this chart. It's called Bowen's Reaction Series, and it is a guideline to how minerals crystallize as magma or lava cools. The rule of thumb is that very dark igneous rocks (volcanic and plutonic) will chart in the upper two sections; if you have a very dark igneous rock, it is probably a basalt or a gabbro because ultramafics are rare in the crust. Dark-grey to medium-grey rocks chart in the intermediate area, while pink/red, light-grey, and white rocks chart in the felsic area.

As mentioned a couple of times above, however, coarse pieces of these rocks are not going to break down quickly enough to have any significant nutritional benefit for your garden. They would have to be either pulverized or sourced from ash deposits.

 photo bowen.gif


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RE: Volcanic rock, any nutrients?

  • Posted by TXEB 9a (My Page) on
    Tue, Apr 16, 13 at 20:02

weirdflowers - interesting! Where does obsidian (perlite) fit in?


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RE: Volcanic rock, any nutrients?

Even though it's black, obsidian is chemically felsic. It technically does not contain minerals though, because of the amorphous arrangement of particles within it (it cools too quickly for crystals to form). There are other forms of volcanic glass though; for example, when basaltic lava is extruded at mid-ocean ridges, it forms pillow-shaped rocks covered in a glassy crust.


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RE: Volcanic rock, any nutrients?

Fascinating.


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RE: Volcanic rock, any nutrients?

Our very old volcanos on the west side of Albuquerque don't seem to support any greater growth of plants nor do other types of volcanic rocks in other areas of the State but guess because of the age, dry climate & type of volcanic rocks they don't break down as readily as those in Hawaii do & support plant growth readily & so soon after eruption. Not sure what the NM types are but know there is obsidian (? "apache tears') & the red 'gravel' type used in landscaping years back.


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RE: Volcanic rock, any nutrients?

"Unless you actually add minerals to your compost, it won't have any minerals in it. It will, however, have whatever chemical components of minerals were converted into living tissue."

WF, I've been puzzling this statement over for a while. Can you expand further on what you mean by it?

I think when we talk about adding "minerals" to soil or compost we are generally not talking about pure elements, because these rarely exist in a form that we would normally be able to source, even if it were desirable to add them in pure form. So for example, when we talk about putting "potassium" in the soil, perhaps in the form of wood-ash, we are not adding pure elemental K but rather potassium hydroxide and maybe other compounds based on K. Various forms of K exist in soil, though I don't know in what forms, and trees and other plants assimilate those compounds. My understanding is that most if not all minerals useful to plants - if they are extant in the soil - exist in complex forms synthesized by soil microbes. The wider the range of useful macro and micro nutrients that have been "digested" by microbes from more elemental forms, the more fertile the soil for plants.

This generally explains why sandier soils are more impoverished than silty and clayey ones, am I right? Where the parent material happened to have a dominant quartz component the commonest particle size ends up no smaller than a quartz molecule, which is very large, and so many of the compounds based on trace elements slip through the profile over millennia leaving an impoverished and droughty landscape.


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RE: Volcanic rock, any nutrients?

I believe I understand the mineral point - it is the exact speciation or combination of elemental constituents that constitute a "mineral" in the true geological and chemical sense, e.g., calcium carbonate, kaolinite, etc. They have a balanced chemical composition, and are naturally occurring. There are over 4,000 specific naturally occurring geological minerals.

In agriculture or nutrition when the term "mineral" is used it is applied more loosely, generally referring to the chemical elements that are essential for a living organism, excepting carbon, nitrogen, oxygen and hydrogen, without regard for the chemical balance or the balanced composition of their occurrence in soil or the organism. Hence we talk about calcium or phosphorous or sulfur or iron or copper as minerals, without regard to how they exist in a balanced compound or salt. Mostly the term is applied to the metals, but it also includes several familiar nonmetals (sulfur, phosphorous, chlorine, iodine, and selenium). Chemically, a more proper term than minerals would be "elements", recognizing that they generally don't occur either in diets are ag applications in their pure elemental form.


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RE: Volcanic rock, any nutrients?

TXEB just about nailed it. There's a couple of other points as well: the chemical components are arranged in a crystal lattice, and the chemical composition can vary but only over a defined range.

Very sandy soils are generally nutrient-poor because even though "sand" describes the size of the particles rather than the mineral components, sands usually are relatively enriched in quartz, whether quartz was a dominant component of the parent rock or not. Quartz is both very hard and, unlike most minerals found in igneous and metamorphic rocks, is extremely stable at surface conditions. So when a rock is weathered and sediments are carried downstream, non-quartz minerals will break up into very tiny grains more easily than quartz, and will chemically weather to clay minerals (which are also soft and easier to break into tinier grains). That's a good enough generalization, though in reality you can occasionally find sands that have very little quartz content in them.


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RE: Volcanic rock, any nutrients?

weirdflowers - guess you don't accept the amorphous ones as "minerals" (e.g., obsidian, opal, etc.). Must be a crystallographer at heart.


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RE: Volcanic rock, any nutrients?

You're right, those ones are mineraloids ;)

I enjoy mineralogy petrology, but I'm not a crystallographer. Actually, I'm halfway through a BS in geology :)

This post was edited by weirdflowers on Wed, Apr 17, 13 at 13:32


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RE: Volcanic rock, any nutrients?

I knew as soon as I suggested that homemade compost would provide minerals, someone would challenge it. Yes, I agree manure and paper would probably not have the mineral content of yard and kitchen waste compost. It was meant to be a general statement.

I agree that w/o soil testing, you can't know for sure. On the other hand, there is also no evidence that one needs volcanic rock minerals either.

I maintain that for the casual gardener, in the absence of actual data showing a deficiency, compost will pretty much take care of your needs. It worked for grampa.


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RE: Volcanic rock, any nutrients?

I was questioning the assertion that compost will always provide every nutrient a plant could use, not that compost has nutrients.


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RE: Volcanic rock, any nutrients?

Yeah, I get that. I think we're on the same page with this. :-]


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RE: Volcanic rock, any nutrients?

As far as my compost goes, I add gypsum, bone meal, Blood meal, Alaska fish fert 5-1-1, Bunny poo tea, very strong bunny poo solids with water, in other words. Egg shells in powder form, shredded leaves, sawdust, veggie scraps and coffee grounds. The compost should be fairly high in some nutrients. I will be starting a new raised bed pretty soon. The Yew shrubs that have been there for 30 + years are getting removed. I will be making a raised bed for shade loving perennials there.


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RE: Volcanic rock, any nutrients?

poaky1 - gypsum, bone meal and egg shells are all high calcium materials. Depending on amounts you incorporate into the compost, the amount of compost you use, and the soil type and pH in which it is used, you could you could be headed for high calcium levels. It's something worth watching for over time.


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RE: Volcanic rock, any nutrients?

I have never had too much Calcium problem on soil test, so I get what you're saying, but I don't think I need to worry for a while. My phosphorous is very low on soil test, I am hoping the bone meal will help with that. The gypsum is of course calcium, my PH is 6.0, I have lots of acid lovers, so avoid lime.


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RE: Volcanic rock, any nutrients?

volcanic rock dust is loaded with what most gardeners and farmers need....healthy soil, healthy plants, healthy people...end of health problems in our country.....it is costly to apply, but your soil builds up so not necessary to keep adding every year....i have noticed my tomatoes need way less water...once a week, or twice if hot weather....let your food be your medicine, plus a little sunshine...i use azomite...can find online about a dollar a pound delivered...alisorganics.com...try out, use 1/2 cup per plant at planting time...the indian


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RE: Volcanic rock, any nutrients?

It's unfortunate that this excellent thread was adulterated by a spam post, but also fortunate in bringing it back to view.

So thanks, indian! Maybe a few more people can read the thread and learn a little from the well-educated participants.


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RE: Volcanic rock, any nutrients?

"The end of health problems in our country." Haha!

Here is a link that might be useful: When a product claims to solve all your problems


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RE: Volcanic rock, any nutrients?

TXEB- in the SW high Calcium may stay like that for a long while. In my Climate high calcium won't stay that way long, unless there is a limestone deposit a few ft down. Pa does have limestone deposits, but I had a dificiency in calcium in my veggie garden before, so I needed to add some to the soil. My Tomatoes get Blossom end rot every year. It effects the first bunch of ripening tomatoes most. It is said to be from low calcium levels. That is my main reason for adding all that calcium.


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RE: Volcanic rock, any nutrients?

Even here in NM we often times find some tomatoes w/blossom end rot. I use Epsom salts around those plants & it works too.... & cheap!


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RE: Volcanic rock, any nutrients?

The fact that Epsom salts works on BER is an indication that it is not directly related to calcium, since Epsom is magnesium sulfate. I get BER on the first few tomatoes and peppers, then it goes away. I have not tried to preempt it with mag sulfate, just never seem to get around tuit. :-]


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