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Re: Nitrogen fixing beans
In article <MOD$971003.14144@rec.gardens.ecosystems>, "Nick LaRocca"
<poly_math@*hotmail.com> wrote:
> Jack Dingler <jdingler@onramp.net> wrote in article
> <MOD$970928.20324@rec.gardens.ecosystems>...
> >
> > Chuck, beans and other legumes fix nitrogen by using nitrogen fixating
> > bacteria that are harbored in root nodules under the soil. So to answer
> > your question the notrogen is already in the bed.
> >
>
> Actually, this isn't quite the whole story. Most of the nitrogen produced
> by the nodule bacteria is immediately absorbed by the legume,
Yes, but there is some leakage from the nodules, on the order of 10%?
(From one or another of my first-year bio books; I can't remember which,
maybe Campbell.) Also, root systems are much less static than the upper
parts, so as the roots keep growing and breaking off, nodules get detached
and returned to the detritus system, releasing even more.
> and that's
> where it stays until the plant is dug in. If you remove the plant and take
> it somewhere else, most of the nitrogen goes with it.
Yes, though don't discount the roots, which can be pretty extensive in some
species. If you carry off the tops and leave the roots behind, you're
still ahead of the game, though not by as much. For me, it's worth not
tilling in the tops, because tilling does me a lot of no-good in turning up
huge amounts of weed seeds, as well as disturbing my little helpers (ants,
worms, beetles, etc.). Mostly I can leave the tops as mulch though, and it
vanishes faster every year.
--
Allyn Weaks allyn@u.washington.edu
PNW Native Wildlife Gardening: http://chemwww.chem.washington.edu/natives/
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