Buckwheat is a great soil builder. I would burn it off mow it and til it under then plant your rape. Thigh high not much is going to grow in that. Cut it low to the ground and then try it.
I would also mow and till before planting. Rape is a great plant to mix with turnips. Deer hit the leafy rape early, then the turnips after the hard frosts. It's a good way to get early season activity on a plots that generally see most of the action later in the season. I just bought some Dwarf Essex rape yesterday along with Purple Top turnips and groundhog forage radish to plant this year.
I will plant my own mix of winter rye/rape/ ptt (60/5/2/lbs/acre) in 2 weeks for the 12th year. Buffet Works great from 8/1 till 5/1.
But with the brassicas already in the blend the oats add a palatable green during a time period the others aren't as sweet. Each to their own and each deer herd can dictate best mix as well.
Here is what me and a friend tried for the heck of it. Tilled up in spring a 1/4 acre plot real good (John Deere 3pt 5ft tiller). Planted buckwheat and mixed in a pound of radishes. Came back two weeks ago and broadcasted some brassicas (Honey Hole). Then I took my zero turn mower and knocked down/mowed the knee high/waist high brassicas. 2 weeks have gone bye and the radishes took off and the brassicas are sprouting. I suspect some volunteer buckwheat as some of it was flowered out when I mowed it. Left a strip standing of buckwheat that we didnt mow, I forgot to ask him how that non mowed strip did. I just like messing around with different planting methods. Ideally I would have mowed and then tilled in the buckwheat. Mixing in oats isnt a bad idea. I mix some oats in with my winter rye planting, but my thoughts rye is better all around.
