Got it, then the grasses build organic matter now, cow peas do the N later. If you have thin topsoil less tillage is better at keeping the organic matter around. Me I have very deep topsoil and pretty good organic matter so I look at other things, and beat the snot out of the ground along the way. ;)
Turnips or tillage (aka oil) radish are getting popular in the mix, they send down a deep thin root and pull nutrients up to the bulb, they kind or recycle nutrients and keep them in the field near the surface. But of course, first you need some nutrients deeper in the soil to start with.... The deeper roots help break up and mellow the ground some in a low or no tillage system.