Interesting. They left out a discussion of grass vs legume. I wonder why. To me that implied ignorance or an agenda to blame global warming and warn about the need to provide the ground with ever more “artificial” fertilizer.
I farm grassfed beef on a very small scale (10+ acres and 15-25 cow/calves). I overseeded a legume blend (clover/trefoil) 10 years ago and have had no problem with nitrogen. I rotate so the legumes periodically go to seed and the field does fine on nitrogen. The bacteria associated with the legumes capture more than enough atmospheric N2 and convert it to a useable form for the both the legumes and the grass.
My limiting factor is actually soil pH, another thing they did not mention, and to a lesser extent other minerals. If the soil gets to acid the plants have a harder time taking up P and K. I sweeten every 3-5years with crushed limestone. I see much benefit from that.
So nitrogen does not have to be the limiting factor as they imply. Certainly it is more expensive to subsidize grassfed beef with oil than it is to use oil to prop up the feedlot model. But it can be done for a price. CO2 doesn’t, to me, seem like even part of the issue (except to the extent it contributes carbolic acid to my pH problem, we can discuss that, too, but it didn’t seem to be what the article was talking about).