If it is mainly maize and rape, there will be various reasons for growing them surely. Rape is mainly grown for the oil which has lots of uses, including as bio-oil, while rape is mainly grown as forage isn't it? They also use it as a cover crop round the edges of fields round here.
I meant tha viability of alternative break-crops. It's all very well taking away the tools that farmers need to make OSR & maize worthwhile, but I think carrot is as important as stick. The more sustainable crops need to be championed as there's far too much stick and not enough carrot around for everything at the moment.
That seems a good idea. If a wider variety of crops could be made viable, alternative crops would certainly reduce the buildup of pests like flea beetle. Round here it seems to be mainly rape and cereals or various sorts. The used to grow field beans occasionally, and sometimes borage, but that is one field somewhere over a good number of square miles.