I run a cover under my small grains, but a whopping 10-15 acres.
I put some urea on ten acres of corn when I could still drive through the corn, I threw in a back of cover crop mix to see what happens. Certainly my one bag will be too light to matter, but just to see if anything comes of it. Good side we had lots of rain this year. Bad side we have so very many weed escapes it's hard to see anything else out there, not sure the cover crop can compete with the weeds, much less the corn.
I see more cover crops use behind peas and sweet corn up here.
I use my few acres for cattle grazing.
Still wrapping my head around the good of it for just plowdown in a northern climate. I want to believe in the positives, but in my short cold growing season, long winters, it's not like we get a green bridge anyhow up here, we get an ice and snow bridge. For decades we're we're taught anything not a crop plant is robbing your grain yield, and even the crop plants that are behind are robbing yield.
Now we intentionally plant stuff in the crop.