Those plants are doing it via symbiosis with soil bacteria. That seems a bit difficult to engineer into other plants, because it involves a lot more than producing a couple of extra molecules, like e.g. BT corn. But then again, I'm not a geneticist.

Absolutely, and it's the reason why even something as lucrative as like white truffles or huckleberries can't be cultivated very easily, if at all.

I don't quite understand what your comment is getting at but I'm interested. Do truffles and huckleberries only grow in nitrogen rich soils?

Oh sorry, no. Truffles grow as part of a symbiotic system around certain tree roots, and it's devilishly hard to recreate those conditions well enough in "captivity" if you get my drift.

Huckleberries are an interesting case and that nobody is quite sure why they fail as a crop, but at the end of the day the only way to grow more huckleberries is to clear woodland and let huckleberries grow there.

http://www.npr.org/sections/thesalt/2017/08/11/542690164/for...

Corn and wheat.

Most of nitrogen is ferilizers and cattle poop. Most of plants grown and farmland used is for cattle.

I don't think farmers would care if they had nitrogen sucking gmo plants for their cattle since they already feed them tons of GMO.

Plants grown for human consumption are invisible in the profiler.

Clover is an excellent nitrogen fixer. I found out by being lazy and not fertilizing my lawn. In a few years I have a lot of clover and much less grass. I was wondering why and found out about nitrogen fixation from air. Granted can't substitute it as food crop but lawns also cover a good amount of area.