I'd echo that...why kill it? It won't compete much and it's roots will foster mycorrhizae (that don't associate with rape) and so help keep the soil buzzing. It's easy enough to control elsewhere in the rotation, but you won't need to. Bees love it too.I've found it doesn't tend to make it through an arable rotation beyond the 1st self seeded year.
But it's the nicest 'weed' to have, and entirely tolerable if you have the choice.