I think it was it chickpeas that tends to put nitrogen into the soil? I vaguely remember my Dad telling me about them ~50 years ago. I've got my Dad's old garden area (~75' x 75') with most of a foot of rich loam but a couple monster pine trees grew bigger over the last 40 years and have shaded out a good part of it. I hate to take those trees down but if I ever intend to have a fantastic garden again, they will need to go. Sad, they have been there all of my life and were right in the back yard near the little chicken house. Kind of like taking down old historic monuments. I've been dragging my feet on taking them down.