From: Archimedes Plutonium

Sean Houtman wrote:


Many nitrogen fixing legumes will shed their nodules in periods of
particular
stress. At those times, the miniscule amounts of Nitrogen available in the
nodules will become available to other plants. In some instances, such as a
plentiful supply of soil nitrogen, they won't form the nodules at all.

Sean

Yes, thanks for the information. A few days ago I dug up some Trefoil to
see what nodules there are. Found many.

Question: if we see a nodule on a plant then are we guaranteed that the plant
fixes nitrogen with the proper bacterium? I wonder about the practice
of the application of inoculants of bacteria. So, if the legume has nodules
is
proof that the field has nitrogen fixing bacteria on those legumes?

There are other things that can cause nodules, not necessarily nitrogen fixing
bacteria. A nodule is a bit like a gall on a root, and galls can be caused by
any number of things. Many nitrogen fixing bacteria do not even form nodules on
their host plants, Shepherdia, Elaeagnus, and Dactylus do not form nodules when
they have bacteria fix nitrogen for them, but they aren't Legumes either.


I wonder about locust trees. I have dug up the roots of a few but never
found anything resembling nodules. The roots are sort of orange colored
outer surface. Is the reason they are orange colored because of nitrogen
fixing bacteria?

Legumes have a kind of hemoglobin called Leghemoglobin, it is red like other
hemoglobins. The orange color is likely other pigment, possibly a carotene of
some sort. Many woody legumes either do not form nodules or they only have them
during certain times of the year.



Question: what does one look for in locust tree roots for the nitrogen fixing
component?

If you want to look for nodules, make sure you look at the finer, non-woody
roots.



Question: do locust trees emit some sort of herbicide akin to what
blackwalnut
emits as juglone?

Not to my knowledge, in other posts you mentioned sap, that sap is just gum.

Sean



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