eyes

I had the same idea about interplanting my corn with red clover as a green manure crop, but I didn't do it, since I wasn't sure then how it would work. Turns out that you're right. These green manure crops add nitrogen to the soil after they've grown, not while they're growing.

Since yours is already planted, maybe the only thing you can do is keep the corn well-fertilized. It's a heavy feeder, as I'm sure you know. Can you mow the vetch between the rows?

I use vetch as a cover crop on my farm. It does produce a lot of nitrogen and loosens the soil making it very easy to till. But you can not grow it together with corn. Vetch will suck every last drop of moisture from the soil and can grow from nothing to a mass of tangled impassable vines in 5 weeks. We do seed vetch into standing corn after the corn is three feet tall so that the corn can be harvested before the vetch takes off. In the garden its better to grow vetch as a cover crop and remove the vines to the compost pile before till the garden next year... Bob.

The vetch will not release its N until it decays... but since it produces most of its own, neither will it steal much N from the corn. Given how rampant it is, the same may not be true of other nutrients... and it is very water-hungry.

Of greater consideration may be the fact that vetch can easily become an obnoxious weed. I would never let it seed in a plot used for vegetables. Sunnfarm's idea of late-planting has merit, since the vetch could be plowed under before it seeds, and would restore some of the N depleted by the corn.

I guess my question is... why vetch??? Why not something which not only improves the soil, but is edible?

Pole beans were planted with corn by the Native Americans, as part of the "three sisters" method. Granted, that was using tall, sturdy field corn, not the shorter sweet corn grown by most gardeners. Tall pole beans would over-power most sweet corn. However, weaker climbers such as "half runners" & some of the "cornfield" bean varieties should do well. I have grown several semi-pole beans that might do well for that purpose.

Cowpeas (a.k.a. Southern peas, or field peas) have also been successfully grown with corn by several GW members. Again, you would want to use some of the less rampant varieties.