Er–coal ash as a soil amendment?

I always knew the Brits were crazy.

Given the justifiable panic over the Tennessee fly ash spill here in the States, it’s almost impossible to believe that people might put anything remotely resembling coal by-products in their gardens on purpose, but they do.

Sounds nuts, I know, but experiments have been ongoing in experiments have been conducted in India, Australia, China, and the United States, Poland, Thailand, and who knows, maybe the North Pole, growing vegetables (or in China, trees) in soil amended with bottom ash. Since ash is almost always quite alkaline (pH>9), this only makes sense in soils that have low pHs, but in those it can raise pH, improve water retention, improve mineralization, and increase nutrient availability. And at normal agricultural application rates (20 tons or more (!) or so on each hectare, which is about 2.5 acres) virtually all of experiments I’ve looked at show that these unlikely amendments are not accumulating at dangerous levels in plants.

Given my suspicious nature, my organic roots, my alkaline soil, and the fact that I haven’t had time to check on who’s funding these experiments, I’m not about to rush out to purchase coal ash for my garden.

Apparently, though, that’s exactly what some people in the U.K. do. A prime source appears to be one’s local chimney sweep, who clears chimneys of soot, then sells it to local gardeners. Soot wouldn’t be bottom ash, and I’m not sure off-hand which of the five or so commercial coal combustion by-products it would most resemble. (I’m not going to take the time to look it up now, since I’m once again late with a major article, and hoping to keep my job.)

But I’m wondering—what exactly is going on? Are people growing vegetables in the gardens on which coal soot gets deposited? Are people who use soot also using coal ash? Has this soil been tested? Come on, all you over there on that island, pipe up. Enlighten us.

8 Responses to Er–coal ash as a soil amendment?

  1. Crazy are we? Hm. I’ll carry on commenting, anyway…
    I’ve heard that soot is good for deterring slugs – this is mentioned in a long thread on a UK allotment gardener’s forum I found just now. There was also that memorable edition of the Radio 4 Gardener’s Question Time last year where a completely mad woman (well, OK, maybe some Brits are crazy) demanded to know where one of the panel members got his soot from. VP talked about it on her blog. Unfortunately you can’t hear the recording any more, but it was a classic. Patient Gardener did a follow-up post on uses of soot, too.

  2. Well, Amanda, its pretty funny that the only response comes from a British ex-pat. Guess I scared the rest of them away.
    Thanks for the links to other relevant posts.
    Oh, and I stand by my claim. I’ve got an e-mail folder entitled “Looney Limeys.” Of course, maybe the folks I hang out with aren’t typical. One can always hope.

  3. Hi Kate
    CBC’s The Current had an interesting segment this morning about the Tennessee coal ash disaster. It probably won’t tell you anything you haven’t already picked up from other media sources, but it was well put together. Apart from the ‘local resident’ guy who seemed to have trouble stringing a sentence together. Already showing the effects of arsenic poisoning, maybe?
    You can listen to it on the CBC site (it’s part three of today’s show).
    The part about the quantities of this waste material that are produced was mind-boggling.

  4. Amanda, you are a veritable fountain of useful information. I am listening now, and am glad that CBC covered this. It’s amazing how many Americans, or at least Bozemanites, haven’t heard of it. Of course, our local paper didn’t cover it, even though as the CBC points out, it may be the worst environmental disaster in US history.
    Go figure.

  5. Oops I’ve been meaning to come over and add a comment, but got a bit delayed by life taking over.
    The chimney sweeps round here give the soot away. We get frequent deliverys up at the allotment site which the ‘old boys’ quickly squirrel away. As Amanda says it’s meant to deter slugs (so I’m told) and it’s dark colour also helps clay soils like we have up at the allotment warm up more quickly in the spring.
    I believe the chimney sweep gives it away because it would actually cost him money to dispose of it via more conventional means. I also met him up at the plot a couple of months ago and he cheerfully give me his home address so I could go and help myself to loads more soot at any time!
    Unfortunately there’s not an easy access to soil testing for heavy metals etc. for the lay gardener. There’s only kits and tests to test basics like pH, potash, nitrogen etc. I’d love to get the soot tested just to see what’s in it. If I could do that, then I’d love to do some experiments to see if the claims for soot’s slug repelling, fertilising, fungus repelling properties etc. actually work.

  6. PS How nice of Amanda to remember me and link to the hilarious Monica Ridley episode and I’m very happy to be filed away in your Looney Limeys folder :)

    I think you’ll find this article really beneficial and interesting. The writer lives in Costa Rica and I have corresponded with him about this topic – he suggested putting additive free crushed charcoal briquets in your garden soil – and guess what – it works – I don’t know why, but the soil gets super fertile and stuff grows twice as big. He’s done it in Costa Rica and I am doing it with my garden.

  8. Has there been any further discussion on this topic this year (2010) it seems everything stopped in 2009?

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