I have been planting a mix of WW, oats, radish, turnips, rape and clovers together in one pass with a seed drill in lightly worked ground for 3 years and have never had a bad stand of the turnips, rape and radish. I'm in the piedmont of NC.
I have 80 acres with 10 permanent stands (2 tripods, 3 ladders, 4 lock-ons and 1 ground blind) and 10 more locations that are cleaned up for portable stands or blinds.
One option and one that I've used is to add clover at brassica planting, mow through spring and summer. Mowing is a must to keep the brassicas from bolting. Terminate everything in late summer and start over.
I used it last year for screening purposes and it did ok for what I wanted. It did not grow as tall as they said it would but that could have been the 70 days without rain. It stood up most of the hunting season and even after it fell it was still tall enough to screen and provide cover for...
I planted LabLab this year for the first time and the deer browsed it but by no means hammered them. I will keep planting it for the simple fact that we went 70 days without rain and you'd have never known looking at the plot.