Dan Whitaker

There are numerous Nitrogen fixing trees/Shrubs.

Goumi - https://en.wikipedia.org/wiki/Elaeagnus_multiflora
Siberian Tree shrub - https://en.wikipedia.org/wiki/Caragana_arborescens
Red Bud - https://en.wikipedia.org/wiki/Cercis_canadensis
Alder - https://en.wikipedia.org/wiki/Alder
Russian Olive - https://en.wikipedia.org/wiki/Elaeagnus_angustifolia
NewJersy Tea - https://en.wikipedia.org/wiki/Ceanothus_americanus

Perennial Tubers/Vines

Groundnut - https://en.wikipedia.org/wiki/Apios_americana
Wisteria - https://en.wikipedia.org/wiki/Wisteria_frutescens

Here is a fairly complete list - http://www.perennialsolutions.org/all-nitrogen-fixers-are-not-created-equal

Enjoy...