Lucerne and Organic Nitrogen

For mineral utilization AND nitrogen fixation, one just cannot go past lucerne. This legume has extraordinarily deep roots and brings up a lot of trace elements. I mainly use lucerne in the walkways, as a good way to utilize what is basically fallow soil. I cut it from an early stage, just as flowers form, and continue to do so from then on. Being penultimate to flowering, then being denied the chance, forces the plant to become biennial. This then affords an in-situ supply of nitrogenous mulch for the beds.
Lucerne, being attractive to aphis, acts as a food source for ladybirds, also as a shelter belt for beneficial insects.
I have tried using clover as a living mulch, nitrogen fixer, but found it to be far too invasive, to the point of rapaciousness as it practically took over the garden.
The old adage " One year's seeding, seven years weeding" holds well for the variety of clover I chose (Subterranean clover). This stuff actually buried its own seed! I kid you not - I have actually witnessed the process.
Peanuts, also a legume (viable seed readily available at the supermarket as 'raw peanuts'), will grow with anything - then probably smother it.
This is a peculiar member of the legume family for the fact that the seeds are produced underground. Not all that dissimilar to subterranean clover, by the fact that it, too buries its own seed, the nuts.
The plants grow to about the size of a basketball, I have found it to be too competitive for space, to be planted in close proximity to most small-crops. However, it does relatively well with quick growing, robust plants like corn, daikon and artichokes, both globe and jerusalem.
Highly susceptible to white-fly, I have had a disastrous attempt at growing it with tobacco, also a white-fly favorite.
In order to produce more nuts, the plants are traditionally 'hilled' to assist with the seed burying process. I have found that, not hilling them, but using them as a 'cut-and-come-again' supply of readily available mulch material, keeps them manageable in a vegetable garden.
I have found an enormous amount of benefit, and amusement, from growing them in poultry forage yards. Chooks aren't all that interested in the growing plant, other then an excellent place to have a dust bath under - and can at times kill the plant. However, once the plant is pulled at harvest, poultry can be kept amused all day long, scratching for the pods, then trying to extract the nut.