A month ago we walked beside a field of very colourful flowers and assumed that these have been planted as green manure.   These are grown briefly in between main crops to recycle nutrients and protect the soil.  It is not as colourful now but there are still some flowers including  Wild Radish,  Phacelia,  Crimson Clover, Field Poppy,  Common Vetch and Flax.   Actually I think the poppies were intruders and probably not in the original seed mix.