Thanks for the photo of nitrogen balls! Ive been surfing, and found this list so far for nitrogen fixing cover crops. Hungarian grazing rye (this from a uk site), red clover, buckwheat, field beans, white mustard.
Also chicken manure and horsemanure. And I guess my rabbit poop would fit in here also.
And I know Peacful Valley is a great source for cover crops.
http://www.groworganic.com/cat...