Question about nitrogen fixing plants

I am looking for Sonoran Desert specific plants to fix nitrogen, but there's only a few ever listed on most places, like mesquite, palo verde, and ironwood for trees, and Bird's of paradise and fairy dusters for bushes, and lupines for flowers. I'm slowly building a list of more legumes to fill in the gap, but the question I had was: do ALL legumes help fix nitrogen? If I simply create a list of all the native legumes I can find, will all of these be useful as nitrogen fixers?

Is there any way to tell which plants are better nitrogen fixers? Observation, certain types of soil in areas where they grow, or more plant life, anything like that? I saw the USDA link one a post here, where they will list a plants nitrogen fixing ability, but for most of the plants I'm looking at, the USDA doesn't have that information yet.

And for non-leguminous plants that fix nitrogen, any characteristics that help find these? Any particular plant families where it's more common to find these? Maybe these are more likely to be listed as 'nurse plants?'

Thanks!

This site has a decent list if some dry land nitrogen fixers and a rough ranking of low, medium and high nitrogen fixation:

http://www.perennialsolutions.org/all-nitrogen-fixers-are-not-created-equal

I am just now planting:
False indigo bush (Amorpha fruticosa)
Siberian Pea Shrub (Caragana arborescens)
Mimosa Trees (Albizia julibrissin)
Feather Dalea (Dalea formosa)

We have volunteer locoweed which fixes nitrogen and is poisonous - so nothing much eats it . I am just getting started with planting - so no results to report.

Shauna, you need to visit the Desert Legume Program. Not only do they have all the info you would ever want about legumes native to the Sonoran desert, they are a seed bank and you can get samples of seeds from them.

And yes, all legumes fix nitrogen. That was a step in their early evolution where they co-evolved with bacteria in a symbiotic relationship.

Thanks for the link, Ardilla. LOL - that's where I found out about the USDA database, actually! But I'd forgotten the percentages estimated for providing nitrogen to the soil that's needed, so good reminder.

And thank you for the link and the info, John. That links new to me - it looks wonderful. I'm very excited to go check it out.