Tree in Field

I have used this tree and whatever crop was in the field before.  This year it was a cereal crop duly harvested.  The field was not ploughed yet this new crop has emerged.  I think it is oilseed rape.  Why?  This field had crops like this a couple of years back and they did grow into that yellow crop, but I'll just have to wait and see, like my friend is doing too.  Been a cloudy day with only a little brief brightness.  This field is by the A66 between Workington and Cockermouth.