Source: Bloody Brilliant!
It’s spring, time to dig in the composts and pile on the mulches, so the blogging world is full of advice and debates about manure. Stuart of Gardening Tips and Ideas has just weighed in on the side of sheep manure, while Elizabeth and Michelle of Garden Rant defend manure against all comers.
Me, I can hardly bear to think about the stuff. The minute I hear the word “manure” I start to twitch and moan; observers report having heard mutterings of “No, no,” and “Tell me it isn’t true.” I wanted to post on this topic (the manure, not the moans) weeks ago, but after the incident with the broken blood-pressure cuff, my doctors warned me not to write about it for at least a month.
It’s all about the stuff they add to animal feed. I stumbled over it when researching the compost article (how else?) and haven’t entirely recovered. Here’s what happened.
Chinese brake fern (Pteris vittata L.) Source: Brake fern remediation
Today I get to write about one of my absolute favorite gardening topics, and for once I’m not being ironic. Phytoremediation isn’t going to make it onto most people’s gardening hit lists, and it’s not a fad that’s going to take the nation’s gardens by storm the way a new rose or hellebore might. But for me it’s proof positive of the extraordinary power of plants; it’s hope in a polluted world; it’s a spot of green in the brownfields of industry; it’s good sense in the midst of madness.
Yes, that’s what I said: thigmomorphogenesis. It may sound like a horrible spontaneous infection or a non-word entirely, the pseudo-scientific version of a thingamabob, but it’s not; it’s the horticultural term for the fact that plants’ growth patterns are altered by physical touch and agitation, whether by wind, rain, snow, contact with other plants, or—and now we’re getting to the heart of the matter—touch. All of these things cause upward growth to slow and stems to become sturdier.
The picture below shows a tree that didn’t get to experience it.
Source: Linda Chalker-Scott, Aug. 2005 horticultural myth on thigmomorphogenesis.
This phenomenon (but not, I’ll admit, the term, which I had to look up) came to mind as I read a recent post at A Way to Garden. Margaret’s comprehensive list of “tips for growing better tomatoes from seed” is all-around useful and informative, not to mention engaging. No surprises there, to anyone who reads her regularly.
Several posts back I mentioned in passing that compost can help fix arsenic in soil, and it seems reasonable to explain what the hell I was on about there. To "fix" arsenic is get it to bond with other, stable molecules so that it can neither leach from the soil into the water supply, nor migrate into your vegetables, and thence into you.
I got onto this originally because the news articles about the great Tennessee coal ash spill of '08 kept mentioning arsenic. Arsenic, I learned, occurs in several different forms, but the one that turns up most commonly in coal ash is arsenate(V), the same form that leaches into soil from telephone poles and fences treated with copper chromate arsenate (CCA).
And yes, at least one recent study conducted at the University of Florida found that when carrots and lettuce are grown in soil that's contaminated by CCA, both vegetables absorbed less arsenic when the soil received plentiful treatments of compost.
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.