Re: [compost_tea] Re: Kudzu
Nitrogen fixing plants are symbiotic with Rhizobium.
This bacterium fixes N using the plant's carbon. The bacteria in the nodule
get the fixed N first. Once their N-requirement is met, then the plant gets
the fixed N, but that N is not in the form of nitrate, nitrite or ammounium.
It is given to the plant as a kind of protein usually.
The plant then has elevated N in it's tissue. It does not release that N as
nitrate - it has spent way too much carbon to obtain that N, and so that N is
retained in the plant.
And thus legumes, or even plants where free-living N fixing bacteria are
present in the soil, will have higher than usual concentrations of N.
The C:N of a plant where nodules are active is 10:1 usually. Maybe 20:1.
And so legumes can serve in the place of manure, or other high nitrogen
containing materials.
Usually free-living N-fixing bacteria don't result in elevated N in the
plant. When the bacteria are eaten by protozoa or nematodes, then the fixed N is
released into the soil as mineral forms.
Hope this helps -
Elaine
Received on Fri Mar 04 2005 - 02:46:01 EST
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