Re: alfalfa for N scavenging

Alex McGregor (waldenfarm@sprintmail.com)
Wed, 04 Nov 1998 17:35:30 -0500

Fred Magdoff wrote:
Not clear why any non-nitrogen fixing alfalfa "scavenger" of N
would be any better than a number of good old N-scavenging grasses.

Ann,

It's true, any grass will absorb that N. Legumes will do it too. All
legumes will stop feeding the rhizobial colonies and they'll be dormant.
The plant invests 25-30% of it's photosynthate to feed these bacteria
when N isn't present in sufficient quantities for the plant.

But legumes are not altruistic. They'll stop feeding them and absorb N
from the soil- a much more efficient way for the plant to produce
biomass. I'm sure that some plants absorb N faster than others- that's
what you need to look for rather than a non-symbiotic legume. I'm
guessing that seed for such a creature is far more expensive than a more
common plant.

Alex

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