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#1
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Volcanic soil
The recent Joanna Lumley programme about Japan visited a volcanic island
in the extreme south where the world's largest radishes are grown. I can't figure out why a pumice rich soil would be any different to vermiculite or perlite, all 3 having the same properties of air and moisture entrainment. No mention of nutrients, but there must be some in volcanic soil? Puzzled...again. --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
#2
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Volcanic soil
"Stuart Noble" wrote in message ... The recent Joanna Lumley programme about Japan visited a volcanic island in the extreme south where the world's largest radishes are grown. I can't figure out why a pumice rich soil would be any different to vermiculite or perlite, all 3 having the same properties of air and moisture entrainment. No mention of nutrients, but there must be some in volcanic soil? Puzzled...again. Volcanic soil is particularly rich in potassium and is of great benefit to potatoes so would guess that radishes would also benefit. Phil |
#3
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Volcanic soil
On 02/10/2016 08:35, Chris Hogg wrote:
On Sun, 2 Oct 2016 07:46:13 +0100, Stuart Noble wrote: The recent Joanna Lumley programme about Japan visited a volcanic island in the extreme south where the world's largest radishes are grown. I can't figure out why a pumice rich soil would be any different to vermiculite or perlite, all 3 having the same properties of air and moisture entrainment. No mention of nutrients, but there must be some in volcanic soil? Puzzled...again. --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus Not sure this is telling you anything you don't already know, but volcanic soils world-wide are exceptionally fertile. The slopes of volcanoes are extensively cultivated for growing crops. The ash in the soils keeps the structure open and free draining, but at the same time retains moisture (that sounds a bit Irish! I'm not entirely sure how it works). The minerals and chemical elements released when volcanic ash weathers further contribute to the range of trace elements available for plant nutrition. I think these things *entrain* moisture, but they don't absorb it. Yes, it's Irish but the amount they can "hold" is phenomenal, and yet they dry to a reusable powder. The idea that you can use them to fill containers on balconies is flawed because, although they seem ideal when dry, they are extremely heavy when wet! IME vermiculite is surprisingly quite alkaline due to the presence of calcium (I think it's on the cation exchange sites, to be boringly technical). I also find it tends to break down and eventually go rather claggy. I use perlite in preference, which should have similar properties to volcanic ash as it's made from weathered volcanic glass, obsidian*. A couple of years ago, I saw packets of some sort of 'rock dust' for sale in my local garden centre, with much printed on the packets as to how wonderful it was for growing plants (BTWSTWT!). Can't remember the trade-name, or whether it was specifically ground volcanic ash or lava, but most quarries with stone-crushing facilities have piles of discarded dust, as it's too fine to be used for roadstone or construction work. Perhaps one of the big quarrying and roadstone groups was branching out. I'm sure if there's a quarry near you, they'd be happy to let you have a few bags' full for nothing if asked. Or you could take a trip to Mexico ATM http://tinyurl.com/gv2lor2 *https://en.wikipedia.org/wiki/Perlite I buy the 100L size vermiculite from builders merchants and, as I have a small garden, I can use it everywhere. Mixed 1-4 with compost it stops the soil compacting and makes it dead easy to weed (things just pull out by hand). What I can't figure out is what it, or volcanic ash for that matter, might contain in the way of nutrients to produce the world's largest radishes! I suppose no amount of feed is any use without a good soil structure --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
#4
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Volcanic soil
tephra which has since weathered to rich soils
I gather tephra is just Greek for ash. So how does ash weather into rich soil? I must be missing something, like where the nutrients come from. Nothing much will grow in ash surely. --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
#5
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Volcanic soil
On 02/10/2016 18:44, Stuart Noble wrote:
tephra which has since weathered to rich soils I gather tephra is just Greek for ash. So how does ash weather into rich soil? I must be missing something, like where the nutrients come from. Nothing much will grow in ash surely. --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus But you can grow in charcoal |
#6
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Volcanic soil
On 02/10/2016 13:16, Chris Hogg wrote:
But the region around Naples, which includes Mount Vesuvius, is very rich mainly because of two large eruptions 35,000 and 12000 years ago that left the region blanketed with very thick deposits of tephra which has since weathered to rich soils. A little more recent than that. The eruption that buried Pompeii dropped several metres of ash, then added a pyroclastic flow. From memory it's over 10 metres at Herculaneum. IIRC the last eruption was 1940-something - late WW2. Andy |
#7
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Volcanic soil
On 02/10/2016 20:04, Chris Hogg wrote:
On Sun, 2 Oct 2016 18:44:06 +0100, Stuart Noble wrote: tephra which has since weathered to rich soils I gather tephra is just Greek for ash. So how does ash weather into rich soil? I must be missing something, like where the nutrients come from. Nothing much will grow in ash surely. It's a slow process, and AIUI two things happen in parallel. Simple organisms like algae first colonise the ash, followed by increasingly more complex plant forms. At the same time, weathering breaks down the ash, releasing nutrients such as phosphate and potash, together with trace elements, and changing the mineral composition of the ash, often to the clay mineral montmorillonite, found in many weathered volcanic ash deposits. Montmorillonite has the ability to absorb cations (pron. cat-ions) such as calcium, sodium, potassium, magnesium etc. and release them slowly over time or as conditions change. The combined effect of these two processes is very slowly to make a humus-rich and very fertile soil. The weathering can take centuries. The island of Surtsea, off Iceland, which appeared between 1963 and 1967, showed signs of plant life in 1965, and is now mostly covered in mosses and lichens, although higher plant forms are now beginning to appear. As they die and rot down, their compost will contribute to the soil and assist other plants to grow. At least, that's what I understand. See also http://tinyurl.com/hqyq36c, http://tinyurl.com/hhf2z5h and http://tinyurl.com/jeq7uk7 Many thanks, Chris. That explains everything! Fascinating stuff, particularly Surtsea, which we're able to observe in real time. 2-5 new species a year. Impressive! --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
#8
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Volcanic soil
On Sun, 2 Oct 2016 21:56:24 Chris Hogg wrote:
On Sun, 2 Oct 2016 21:20:18 +0100, Vir Campestris wrote: On 02/10/2016 13:16, Chris Hogg wrote: But the region around Naples, which includes Mount Vesuvius, is very rich mainly because of two large eruptions 35,000 and 12000 years ago that left the region blanketed with very thick deposits of tephra which has since weathered to rich soils. A little more recent than that. The eruption that buried Pompeii dropped several metres of ash, then added a pyroclastic flow. From memory it's over 10 metres at Herculaneum. IIRC the last eruption was 1940-something - late WW2. Andy Well, yes, but it doesn't say they were the only eruptions, just that those were the ones responsible for the soils of the area. Vesuvius eruptions listed here http://tinyurl.com/j85lp76 Er, that takes us to a Google list for Jenolite! At least it does on my computer! David -- David Rance writing from Caversham, Reading, UK |
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