I think it matters if the volcanic soil is based on ash(atmospheric deposition), eroded pumice, or eroded lava. Here in Wisconsin, we have heavy clay soil, presumably deposited when this area was the floor of an ancient sea. We also have limestone beds buried beneath the soil. Some volcanic soils are acidic, due to the sulfur content, and this makes the soil suitable for acid-adapted plants, like azalea, rhododendron, and blueberry. My experience with growing blueberries is that heavily amending our soil with compost made from shredded leaves, and adding agricultural sulfur to lower soil pH, gives good results. I know that acid loving plants can be found growing near volcanoes, so they must be adapted to volcanic soils.

soils of volcanic origin are called andisols. tend to be fluffy (ease of root penetration/growth), of high natural fertility, and excellent water holding capacity. some limitation of phosphorous availability, but that is easily managed.

Volcanic soils can be very good soils to grow plants in when the pH is in the range plants need and they are better when adequate amounts of organic matter are added.
Some time back people were conned into purchasing Volcanic soils to improve their soils and many found they had simply wasted their money on a magix elxar that did little. Where volcanic soils are they can be good soils, and made better with the addition of organic matter.

Here is a link that might be useful: About volcanic soils

There's really no concern about the pH being too low in my area, since soils are generally in the neutral or alkaline range anyway (I read that the problems with phosphorus availability are only in acidic volcanic soils).

I'm already using a black scoria that I collected mixed with some peat and/or compost as a potting mix, with good results. I just have not made the leap to collecting enough to use in the garden. It sounds like kimmsr is saying that would be a waste of time anyway... that it's good soil only where it is the native material?

I have created a good garden soil out of the dry clay that I have to work with, but it sure eats up organic material quickly, and well, it acts like clay. I would love to add some porosity and water holding capacity, and wonder if this is still possible with a volcanic cinder/scoria/pumice-type material...

Thanks for the feedback

what is your greatest limiting factor? i'm guessing it's water.

the phosphorous limition is partially related to pH, but more greatly related to age. as soils go, these are young, and to mature through the three forms of soil phosphorous is a function of time. again, easily managed.

a good primer on soil characteristics in general is by Weil and Brady, Elements of the Nature and Properties of Soils.

you sure you have a granite based soil? granite is a coarse textured material

as to whether or not you should, I have two answers. first, if it's not costing you much, what have to got to lose? a little exercise? an existing soil i'm going to guess you complain about?

second, if you question the validity of adding the stuff, i'd run three soil tests...a sample of existing garden space, a sample of what you'd haul in, and a sample of the two mixed.

now for the trick question...do you know your soil profile?

Assuming, as dangerous as that is, it has a rough texture, which would make similar in texture to crushed granite sand, which is totally different from washed pit sand, it may help loosen your soil

To learn the facts for your region, contact your county's Extension Service office.

Uses this clickable map to do so:
http://www.csrees.usda.gov/Extension/

Here is a link that might be useful: locate your Extension Service office

Strobiculite: I say my soil is of granitic origin because I'm at the base of a large mountain range (the Sangre de Cristo Mountains of the Southern Rockies) that in my area is granite and granite-type rock. My soil is what is locally called adobe soil, fine grained clayey soil, I'm guessing a result of decomposition over time of the high proportion of feldspar in the local granite (most of the rock appears pink from the feldspar in it). The hillier areas have granite outcrops and there the soil is much coarser grained but still has a clay component.

I'm also pretty familiar with my soil profile, having studied the various layers in several deep excavations I've had to make for various reasons.

So, to make a long story short, I like your idea that it doesn't hurt to try the amendment. As RpR guesses, the scoria I have in mind is certainly rough in texture and will almost certainly loosen (and lighten) the soil, as well as provide better aeration.

Thanks for the input...

Managing Adobe (clay) soils is best done by adding enough organic matter to that soil. If things such as sand, or volcanic rock, are to be added that needs to be in pretty hefty amounts to make enough of a difference and not create more problems and adding more mineral content to the soil will not do much for the Soil Food Web which needs organic matter to live on.
Perhaps the link below will be of some help and maybe this article by Keith Baldwin may also,
http://www.finegardening.com/how-to/articles/improving-clay-soils.aspx

Here is a link that might be useful: Managing clay soils

ok, i'm jealous. feldspar....hmmm, having a private moment here.

there anyone in your area who is growing produce, flowers, alfalfa, anything on any kind of scale? that you could talk to, buy them a few cups of coffee, bring them some donuts, and learn what they say are the "tricks" to production in that area?

because my experience has been...there are many people willing to tell you what they think, especially if they do not have to a) do the work or b) pay for it. and because of the nature of plants and growing them, just about anything you do is likely to at least not yield adverse results.

if you've done stuff like this before, under different applications, give it a shot. try a small area, see how it goes. onecof my personal theories is, unless you know it's going to work, use a light hand. that way, even if the experiment is a complete and utter failure, you don't do something irreversible.

off the top, i'd say you got a decent handle on your local conditions.

still not sure why you got to complain about clay, but that's a personal issue, one they don't make medication for.

kimmsr:
Thanks for those good links. Fortunately I have pretty much done what they describe, partly without knowing it.
strobiculate:
Thanks for the wise words. I did not mean to complain about my clay soil, it is actually quite good (extremely deep, retains moisture and nutrients well, is not hard at all to work if treated right). I have had very good results over the years, even though most (though not all) of the local growers are in areas with wonderful loamy soil along rivers.

I guess I'm always thinking of trying something new, some improvement that would benefit a wider variety of plants. I think I will just try this out as an experiment... thanks for the encouragement!

If the expense is little, then why not try it? The material you have access to may be valuable mineralogically. I reckon it goes without saying that no soil system is highly productive without a certain level of OM, which itself depends significantly upon moisture-holding capacity of the parent material, as well as climate if irrigation is not involved.

I don't know if volcanic soil is all that important, in and of itself. Which is to say, I read things that suggest if it is too new, or, has the wrong elements as the majority of its elemental makeup, it can be harsh on the plants.

Also, there are many places in the United States where there is a lot of volcanic soil. But, the place known for growing the biggest vegetables has less volcanic activity than many others, a shorter growing season, and the growing season is generally cooler with less sunlight by strength. What it does have is, for a while, a lot more sunlight by sheer number of hours, during the primary growing season.

But, you know, if you have access to volcanic soil, it probably wouldn't hurt to 1) Inspect any plants around the area to see how hardy they are and what sort they are; and, 2) go ahead and bring some home for a test run. And, if you are mixing it with other things, like compost, horse manure, potting soil and/or soil from your own yard, it will most likely be okay.

Help please my garden so fail this year. Thank you RoseMyarMy first time asking anything in here. We have bought off grid property east of Flagstaff Arizona in the Sunset Crater area. We really have no dirt it's fine volcanic pebbles. Real nice to lay in but not to grow veggies in. We have very little rain and summer temps this year were in the triple digits, winter's we get a few inches of snow come Dev. Jan. But temps stay atpund 30s days in teens knights. How do I make my garden grow. What can I add. Oh and we haul water

Thank you Arizona

It sounds like you need to either build up your 'soil' with a lot of organic matter, or import some topsoil.

If you are able to haul a truckload of something like manure, barn cleanings, compost, wood chips, etc. it would be a great start.

Do you know what the pH is out there? Arid regions are usually alkaline but volcanic soil may not be.

I would also recommend you look for an Ag Extension office, or Master Gardeners in your area or in Flagstaff. They may have some good local advice.

Do you have any neighbors with gardens? Maybe ask them what they are doing.