I don't know who developed it, but there is an alfalfa variety known as
"Nitro" that is a good nitrogen-fixer and supposedly so non-dormant that
it reliably winter-kills. In my own garden (in Southwestern Idaho) I
found this not to be the case...but I am digressing. The seed industry
is so customer-driven, that very little effort goes into niche-market
products, like green manures. But maybe there isn't a need. There are
so many good green manure and cover crop species. But rest assured, if
there is a market for varieties like this, someone will develop them.
Regarding your other question in your private post about corn varieties
for organic production, our regular corn hybrids should do well under
these conditions. Good agronomic characteristics transcend the
(perceived) organic/conventional division. I'll bet that modern corn
hybrids will greatly outperform OP landrace corn varieties even in
primitive production systems, although I am not sure about extremely low
nitrogen environments. Anyone interested in setting up a few trials on
this with me?
Margaret Smith at Cornell is working on corn that does well under low
nitrogen conditions. You can bet that as nitrogen application is
restricted (for whatever reason) the seed industry will develop
varieties that need less nitrogen fertilizer.
Dale Wilson, Pioneer Production Research