Simulating Italian Volcanic Soil - How?

svirfnebliDecember 17, 2010

Hi all,

I've taken it upon myself that I'm going to learn how to can tomatoes to make good italian sauces and nepoletano pizza. So i'm starting this year with growing several cultivars of San Marzano varieties to see what I like best. I'm trying for 6 different cultivars.

I have built some large planter boxes (8 x 4 x 2) and want to fill it with an appropriate soil for this tomatoes. San Marzano's are often described as being being grown in volcanic soil - specifically in the "shadow of mt vesuvius".

What is the best way to emulate this volcanic soil? I'm assuming the Volcanic part is Ash based, and not rock based. I've not have much luck looking online for italian soil information.. Any help is appriciated.

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I see many references to volcanic soils being very rich but little real information about why, ie soil test results. Some few people have specualted that those soils are rich because of the amount of oganic matter that is in them from the vegetation that was cooked as the lava flowed.

Here is a link that might be useful: Volcanic soils

    Bookmark   December 18, 2010 at 6:48AM
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tapla (mid-MI z5b-6a)

There are 2 separate parts of your question to consider. The first is 'What is it about these soils that might set them apart from other soils from the nutritional perspective?' The second part is 'What is it about these soils that might set them apart from other soils from the structural perspective?' Your challenge is to determine which deserves your attention. Of course, things like light/day length/temperature and weather patterns all have impact, but you're ability to change those things is minimal, where you have considerable influence over the soil's structure and your nutrient supplementation program.

I grow a LOT of herbs and other perennials in a soil that looks like this:

Don't be put off by it's appearance, it's EXTREMELY productive when used with a suitable nutritional program, as a large group of GWers will witness to.

There is another soil that many use for tomatoes with very good results that is made with pine bark fines with a little peat and perlite. Almost all that have used either of these soils are extremely happy with their choice, leaving peat and compost-based soils behind & never looking back.

I'll leave you to your studies and to determining what significant nutritional issues there might be, but if it's soil structure that makes the difference, then it's probably to be found in the drainage/aeration properties of the soil.


    Bookmark   December 18, 2010 at 11:04AM
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As Al has said, there are many other factors that determine flavour other than soil. From my own experience, living in different countries, the character and flavour of the same vegetables are not the same.

A grated daikon from my garden doesn't have the same pungency as one grown in Japan. Interestingly, they also have volcanic soil. My son had a meal in Norway that included brussel sprouts. He cannot stand brussel sprouts but in this case, he ate them and they tasted good. Different soil, different climate, different cook. Who can tell what the factor is?

You can buy volcanic rock, crush it and add it to your raised beds. I would still use soil and compost unless you are very diligent with fertilizer and watering. The advantage of high CEC material such as compost is its buffering or storage capacity for nutrients and water.

I don't think you will get the same flavour in your tomatoes, no matter what you add, as the tomatoes grown in Italy. Just enjoy your fruit and be happy.

Here is a link that might be useful: Soil Development in Volcanic Ash

    Bookmark   December 18, 2010 at 12:22PM
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wayne_5 zone 6a Central Indiana

You could try what I am going to try. I ordered some Azomite rock powder from Fedco Seeds. You sprinkle some on the surface and work it in. It contains trace minerals. I believe it comes from a location in Utah and whether it is volanic, I am not sure. If it performs like the post reply I entered on the Organic Gardening Forum under "Is Rock Dust Safe?", I will be happy.

    Bookmark   December 18, 2010 at 1:21PM
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I think you're mistaken to assume a volcanic soil is "ash based". Mt. Vesuvius ejects a lot of ash when it erupts, but even larger quantities of lava, silica, and pumice. Volcanic soils are rich in potassium, phosphorus, and sulfur, and all kinds of trace minerals, which make them so ferile. They are also extremely well-draining, due to the porous nature of the pumice and relatively large particle size. If you try to replicate this type of soil structure-wise, you will probably have to water and fertilize frequently.

This was a fun question to research, but you're right, I could find no information specifically about trying to re-create volcanic soils or the growing conditions around Mt. Vesuvius. You're probably going to have to experiment. If it were me, I would probably start with a pumice-based growing medium... maybe pumice, granite grit, and a bit of sand? Getting the fertilizer just right will also be a challenge.


    Bookmark   December 18, 2010 at 4:44PM
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wayne_5 zone 6a Central Indiana

I did a Google search for Azomite. It is from an old volcano and seabed deposit.

Here is a link that might be useful: Azomite

    Bookmark   December 18, 2010 at 5:44PM
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Maureen is RIGHT! Coffee plants like low pH soil, high in sulfur. Colombia,Brazil & Hawaii all grow fine coffee on old volcanic soil. Central Texas in USA, is on top of very old volcanic soil.
I say go for it if you find the right mix, then write a book & sale the recipe for the mix. Good Luck

    Bookmark   December 18, 2010 at 8:39PM
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jolj - I live in central Texas. I don't know whether this area has any volcanic rock or not, but we do have a high pH problem (7 to 8.) I spoke with a liquid fertilizer producer once, and he commented to me that they used ammonium sulfate instead of ammonium nitrate to help lower the pH; it made the phosphorus more available to the crops, thus reducing the the amount of phosphorus that they had to apply overall.

Last year I grew BUSHELS of tomatoes: all hybrids (Better Boy, Super Fantastic and Celebrity) except for a few Romas. This year I'm trying San Marzano, Big Rainbow, Jubilee, Purple Calabash, Brandywine, Great White, Beefsteak and Better Boy. I think I had good success last year because of the sulfur and the native tree mulch I worked into the soil.

Both my spring and fall crops did beautifully, despite the 100 degree days in summer. We have heavy blackland clay soil here, and I've worked a lot of sand into it, along with several piles of compost. I'm waiting until late February before I attempt to plant; we've had some REALLY unusually cold weather here as of late. I hope that changes soon, my tomato plants are outgrowing their pots.

If I can't get the San Marzanos to produce decent tasting fruit, I'll let you know. I'd even crush up volcanic rock out of my flower beds with my chipper and work THAT into the soil if I thought it would help, but I'm going to use a wait-and-see attitude. Please let me know if anyone comes up with any ideas.

    Bookmark   February 8, 2011 at 4:25PM
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tapla has been at this for some time, so I would go with what he said.
cowgril2, thanks for the link.
wanye 5- AMEN!!!
bjustice-search "Ancient Volcanoes", I do not remember if the map show the towns in the fall out or not.

    Bookmark   February 8, 2011 at 7:22PM
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snidelywhiplash(z5a Nebraska)

Hhhmmm....reading the analysis for Azomite, it sez that its five highest-percentage contents are:

Silicon dioxide 65.85%;
Alumina (aka aluminum oxide) 11.43%;
Potassium oxide 5.23%;
Calcium oxide (lime) 3.67%;
Sodium oxide 2.07%;

And a jillion trace elemental metals. Can't speak to the value of the trace elements, but the vast majority of the stuff - over 75% by weight - is basically good ol' SAND. : )


Here is a link that might be useful: Azomite Certificate of Analysis

    Bookmark   February 10, 2011 at 12:30AM
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wayne_5 zone 6a Central Indiana

Well, it's the trace and micro elements that I'm cobalt, yttrium, strontium, and some others. The silicon is more useful for plant stem strength than you realize.

    Bookmark   February 10, 2011 at 9:55AM
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This year I am going to add some pulverized volcanic rock to the soil where I plant my San Marzano tomatoes. I couldn't find much info on the Italian soil they are grown in either. Every year I do a new experiment with my garden. Sometimes I hit on something good, but not always. I always add a crushed egg shell to the hole where I plant my tomato and I no longer have blossom end rot. That adds calcium. That was one year's experiment.

    Bookmark   April 23, 2011 at 5:52PM
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AMAN again, wayne 5.
Micky, I am not a soil Dr. & I have no ideal if egg shells break down into usable nutrients or not. I compost them, because they do not hurt the soil & the land fill is overflowing.
There is a thread on one of these forums & almost everyone said that we are not getting our calcium from egg shells, & not in one year anyways. Yes I still compost egg shells, tea & coffee bags. Some one said that coffee slows the growth of plants to.I covered the ground with 12 inches of fresh roasted,ground coffee. I did this to kill the weeds & grasses & to compost the waste coffee. The grass grew though the 12 inches & is green & spreading.
So you can not believe everything on the net.
BER is caused by more then one thing, watering & heat play apart in it. I lime & put egg shells in my garden & never had BER here in S.C., in 30 years.

    Bookmark   April 23, 2011 at 11:12PM
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This is my first try at San Marzano tomatoes. I have done research and have read about pumice. You can buy 40 pound bags of pumice at Souther States farm store. It is used in horse stalls to keep them dry. The product is called Dry Stall. It is 17 dollarls a bag. Check it out.

    Bookmark   May 5, 2013 at 2:33PM
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I wanted to know how svirfnebli your tomatoes turned out?

I also am starting San marzanos for pizza napoletana and wanted to hear what the verdict was?


    Bookmark   June 19, 2014 at 1:46PM
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tropical_thought(San Francisco)

I think you need to collect from volcanic soil from a site. It would have broken down lava in the soil.

    Bookmark   June 20, 2014 at 12:02PM
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