Oh I'm probably just wrong about the moringa nitrogen fixing then. I've got a packet of the tithonia rotundifolia waiting out for spring. 
I tried red cowpeas for a cover crop but we have a huge issue with invasive Russian bindweed here, as well as it's cousin morning glory, and they just took over the field. I learned from it though and have better plans for more direct watering next season that I think should help.