Back in the 1980's I was interested in growing naked seeds pumpkins in corn, building off of the "corn, beans, squash" trilogy. Intercropping can have benefits, with the different crops utilizing the available time and space more efficiently than when grown in monoculture. I had trouble making it work, the naked seeded pumpkins I had yielded much less seed than when grown by themselves, and wanted to climb the corn and break it down. At the time, I moved the naked seeded pumpkins to their own project, and started looking at bush cowpeas as another idea.
My first crosses were between shade tolerant vining cowpeas, and early bush varieties. The vining parents were Chinese Red, and a PI from Africa (offered in SSE) that had wild characteristics like explosive pods and more hard seeds. I don't remember what the initial bush variety was, I think it was from SSE and it was a PI from another country with cream colored seeds, but later I used early varieties developed in MN, also from SSE. Over the years I've selected for bush habit, strong upright pod stems so they are easier to pick and also stay off the ground, and every few years that they can mature under a full corn canopy. I plant the corn rows about 3 1/2 feet apart, so I can get in to harvest the cowpeas in late summer. The cowpeas are planted a couple of weeks after the corn, in a 6" grid, so they fill in quickly and shade out weeds. The cowpeas mature in about 70 days.
This year I'm evaluating some new crosses, at the F-2 or F-3 stage. The photo shows three different lines of cowpeas, in the space between the corn rows.