Subject: Re: Nitrogen fixing beans
From: "Todd M. Bolton" <tmbolton@erols.com>
Organization: Todd Bolton Associates, Inc.
Date: Sat, 11 Oct 1997 16:57:20 -0400
Message-ID: <MOD$971011.5846@rec.gardens.ecosystems>
References: <MOD$970927.29878@rec.gardens.ecosystems> <MOD$970928.20324@rec.gardens.ecosystems> <MOD$971003.14144@rec.gardens.ecosystems> <MOD$971006.15925@rec.gardens.ecosystems>
Allyn Weaks wrote:
>
> In article <MOD$971003.14144@rec.gardens.ecosystems>, "Nick LaRocca"
> wrote:
>
> > Jack Dingler 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.
Accordong to NRCS "Nutrient Management" booklet dealing with
conventional farming and the amount of reduction in N fert if the field
is put on a legume rotation. The first year alfalfa is planted it
allows reducing N fertilizer app by 100 to 140 lbs. per acre. This is
out of a range of 90 to 160 lbs acre normal application for high yield
corn.