We used to plant it as a cover crop for the pheasants on the shooting estate I worked on.
I spent one summer pulling up a quarter of an acre by hand, my then bosses bullshit job of the month to keep myself and the other under keeper busy while he was on holiday 🙄
The pheasants seemed to like it to hide in same for Quinoa the pheasants like the seeds.
I don’t know what they use now but we used to sow acres of the stuff for very little money so some one is making a good killing on this stuff!
Found a supplier
http://www.bostonseeds.com/products/12/Game-Cover-Crops/124/Top-10-Best-Selling-Game-Cover-Products/#product765
Traditional Game Cover Mix
Contains Maize, Red & White Millet, Buckwheat, Kale, Sunflower, White Mustard, Forage Rape, Gold of Pleasure and Phacelia.
you trendy types can grow your own with the above link 10 Kg of seeds will plant an acre!