Here's what EDIS/IFAS has to say (emphasis added):

"...To be most beneficial to the garden, the cover crop must be plowed down (or added to a compost pile) so that this "captured" nitrogen can be released by the process of nitrification. Allow a few weeks time between plow-down and planting in your garden. Early investigations proved that the greatest benefit was achieved when the green manures were incorporated at the half-grown stage. At this stage there is more nitrogen available and fewer problems related to soil-borne diseases..."

Here is a link that might be useful: Publication #EES113

The cow peas (black eye peas) are growing. It is recommended to turn it under at the half grown stage. But what does that mean? Since the big benefit is in the roots, I speculate that when the pod starts to form the roots might need to be at their apex. But that is speculation. Does anybody know? Thanks.

Hi Shavedmonkey, the raised bed looks nice and the peas look healthy, I hope that this info answer some of your questions.
With some of the peas that I grew the past season, I just cut them leaving the roots and putting hay on top, they will be ready for planting soon.

Silvia

Here is a link that might be useful: green manure